The Caracal
The caracal /ˈkærəkæl/ (Caracal caracal), also known as the desert lynx, is a wild cat widely distributed across Africa, central Asia, and southwest Asia into India. In 2002, the IUCN listed the caracal as Least Concern, as it is widespread and relatively common. The felid is considered threatened in North Africa, and rare in the central Asian republics and India.
German naturalist Johann Christian Daniel von Schreber first described Felis caracal in 1776 from a specimen collected from Table Mountain, South Africa, which is considered the type locality of the species. The generic name Caracal was first used by the British naturalist John Edward Gray in 1843 on the basis of a type specimen collected near the Cape of Good Hope.
The caracal has been classified variously with Lynx and Felis in the past, but molecular evidence supports a monophyletic genus closely allied with the African golden cat and serval.
Nomenclature
The word caracal is derived from the Turkish words kara kulak, which means "black ear". In Persian, the caracal is known as siyāh-gōsh, also meaning "black ear". In North India, it is known as syahgosh.
It is also called African lynx, Asian lynx and desert lynx, though it is not a member of the genus Lynx.
The local Toubou name is ngam ouidenanga, meaning gazelle cat. In Afrikaans, it is called Rooikat, which means red cat.
Characteristics
The caracal is distinguished from Felis by the presence of a long tuft on the tip of the ears, exceeding half their length. No trace of pattern remains in the coat, except a few spots on the underside and inside of the fore legs. It is a slender, long-legged cat of medium size with a relatively short tail. The fur on the back and sides is generally of a uniform tawny grey or reddish, frosted-sand colour. The belly and the undersides of the legs and chest are whitish and spotted or blotched with pale markings. The tufted ears are black-backed. Black caracals also occur. The skull is high and rounded. The jaw is short, stoutly built, and equipped with large powerful teeth. About 92% of caracals lack the second upper premolar teeth. Males reach a head and body length of 75 to 105.7 cm (29.5 to 41.6 in), with a 23.1 to 34 cm (9.1 to 13.4 in) long tail, and weigh 8 to 20 kg (18 to 44 lb). Females are smaller with a head and body length of 69 to 102.9 cm (27.2 to 40.5 in) and a tail 19.5 to 34 cm (7.7 to 13.4 in) long. They weigh from 7 to 15.9 kg (15 to 35 lb).
Facial markings comprise a dark line running down the center of the forehead to near the nose, and another one running from the inner edge of the eye to the nostrils. The pupils of the eyes contract to form circles. A light-colored ring encircles the eyes, and a rather indistinct dark brown patch occurs over each eye. White patches occur on either side of the nose. The inner surface of the pinna is covered with small white hairs. Numerous stiff hairs emerge from between the pads and probably are an adaption for moving through soft sand.
Distribution and habitat
Caracals are common in parts of their sub-Saharan African range, especially in South Africa and southern Namibia, where they expand into new, and recolonize vacant, areas. They occur at much lower densities in Central and West Africa, where the carnivore community is more diverse. They occupy a wide variety of habitats from semidesert to relatively open savanna and scrubland to moist woodland and thicket or evergreen and montane forest such as in the Western Cape of South Africa. They prefer drier woodland and savanna regions with lower rainfall and some cover. They also occur in the Saharan mountain ranges and semiarid woodlands. On the Arabian Peninsula, caracals occur throughout the mountain ranges and hilly steppe regions, but probably do not penetrate far into the great sand deserts of the interior.
The Caspian Sea, Ustyurt, and the Aral Sea constitute the northern distribution limit of caracals, which barely extends east of the Amu Darya. In Turkmenia, caracals were known from the coastal plains at the mouth of the Atrek River to the foothills of the Kopet-Dag, along the Tedzhen River, in the deserts along the Murghab River and east of the Kushka River. Their range extends southeastwards through Iran, Baluchistan, Punjab, and central India to Uttar Pradesh.
Distribution of subspecies
Subsequent to Schreber's first description of a caracal from South Africa, several subspecies were described, of which these are recognized today:
C. c. caracal (Schreber, 1776) – inhabits South Africa.
C. c. nubicus (Fischer, 1829) – inhabits Nubia.
C. c. algira (Wagner, 1841) – ranges from Algeria through Tunesia to Morocco.
C. c. lucani (Rochebrune, 1885) – ranges from Angola to north of the Congo River basin.
C. c. schmitzi (Matschie, 1912) – ranges from the Dead Sea region through Syria and Pakistan to India.
C. c. poecilotis (Thomas and Hinton, 1921) – inhabits northern Nigeria.
C. c. damarensis (Roberts, 1926) – inhabits southwest Africa.
C. c. limpopoensis (Roberts, 1926) – inhabits Transvaal.
Russian zoologist Heptner described C. c. michaëlis in 1945 from the western Karakum.
Ecology and behaviour
Adult caracals are solitary, but have also been observed in pairs. They produce the usual range of sounds for cats, including growling, hissing, purring, and calling. Unusually, they also make a barking sound, which is possibly used as a warning. They scent mark their territory, leave faeces in visible locations, and mark territory by spraying urine onto bushes or logs, or raking it into the ground with their hind feet.
Their home ranges are large in arid areas. Three males averaged 316.4 km2 (122.2 sq mi) on Namibian ranchland.[16] In northern Saudi Arabia, a radio-tracked male ranged over 270 to 1,116 km2 (104 to 431 sq mi) in different seasons.[17] In an agricultural area in Israel's Negev Desert, male home ranges averaged 220.6 km2 (85.2 sq mi). Home range size was positively correlated with body weight, and negatively correlated with prey availability. Male home ranges overlapped substantially (50%), and typically included those of several females. Two dispersals were observed: a male migrated 60 to 90 km (37 to 56 mi) south before establishing a home range, whereas a female remained in the vicinity of her natal range, with her range partly overlapping that of her mother. Twenty caracals, several of them transients, were found to use an area of 100 km2 (39 sq mi) with some ranging outside this area, making for a relatively high local density despite the large home ranges. Male home ranges in better-watered environments of South Africa are smaller. In the West Coast National Park, South Africa, home ranges of two males averaged 26.9 km2 (10.4 sq mi), and those of three females 7.39 km2 (2.85 sq mi). Male home ranges overlapped completely with those of females, whereas female ranges overlapped between zero and 19%. Caracal were active by night and day, and significantly longer on nights colder than 20°C. Males moved more than twice the distance of females during an active period.
Caracals can survive without drinking for a long period—their water demand is satisfied with the body fluids of prey. They are known for their ability to capture birds by leaping 2 m (6.6 ft) or more into the air from a standing start. They hunt by stalking their prey, approaching within about 5 m (16 ft) before suddenly sprinting. They kill smaller prey with a bite to the nape of the neck, and larger animals by biting the throat and then raking with their claws. They sometimes cover larger prey if they cannot consume the whole carcass in a single meal, and return to it later. Some have even been observed to hide carcasses in trees. They live mainly on prey smaller than 5 kg (11 lb), including hyraxes, springhares, gerbils, mice, and birds. They are capable of taking antelopes, including species such as mountain reedbuck, springbok, common duiker, and steenbok. Occasionally, they tackle adult goitered gazelle.
Reproduction and lifecycle
Mating occurs year round. In the Sahara, breeding is reported to occur primarily in midwinter. Estrus lasts 5–6 days. Females copulate with several males in a "pecking order" which is related to the age and size of the male. One female was found to have mated with three different males during every estrus period, each time the same individuals in the same sequence. In some areas, males have been observed to fight aggressively for access to females and to remain with one for several days to guard against rivals; in others, they appear to be less protective. Copulation can last from 90 seconds to 10 minutes.
Gestation lasts from 69 to 81 days, and litter size ranges from one to six kittens. Females use caves, tree cavities, or burrows as shelter when giving birth. Newborn kittens weigh 198 to 250 g (7.0 to 8.8 oz), and open their eyes between four and ten days of age. Kittens venture outside the birthing den at around one month of age. Their deciduous teeth are fully developed at the age of 50 days. They are weaned at about 10 weeks. At around four or five months, the canine teeth appear, with the others following over the next six months. The young stay with their mother for up to one year, when they start to reach sexual maturity. In captivity, they have lived to be 16 years old.
Threats
Habitat destruction due to agriculture and desertification is a significant threat in central, west, north, and northeast Africa where caracals are naturally sparsely distributed. It is also likely to be the main threat in the Asian part of its range. As caracals are capable of taking small domestic livestock, they are often subject to persecution. Severity of depredation appears to be dependent on the availability of wild prey and husbandry techniques.
In Iran, the killing of small livestock has brought the caracal into serious conflict with local people, who sometimes make efforts to eradicate it. The cat has never been recorded to be killed in road incidents, and no severe poaching pressure on it appears to happen.
Conservation
Populations in Asian range states are included in CITES Appendix I; populations in African range states are included in Appendix II. Hunting of the species is prohibited in Afghanistan, Algeria, Egypt, India, Iran, Israel, Jordan, Kazakhstan, Lebanon, Morocco, Pakistan, Syria, Tajikistan, Tunisia, Turkey, Turkmenistan, and Uzbekistan. In sub-Saharan Africa, the caracal is protected from hunting in about half of its range states. In Namibia and South Africa, the caracal is classified as a "problem animal", which permits landowners to kill the species without restriction; nonetheless, caracal have persisted and remain widespread.
In captivity
As of November 2009, 18 caracals were kept in 12 AZA-accredited institutions participating in the Population Management Plan.
In culture
Caracals appear to have held some religious significance for the ancient Egyptians. They were found in wall paintings, their bodies embalmed, and sculptures of caracals and other cats guarded tombs.
Historically, caracals have been used in India for hunting and blood sports. A popular sport in India was to have a captive caracal set upon a flock of pigeons, whereupon bets were made on how many birds could be taken down by the cat. A practised caracal could ground as many as a dozen birds. Today, as well as in the past, caracals have occasionally been kept as exotic pets in Africa, India, North America, and elsewhere.
The Caracal Battalion is a unique combat unit in the Israel Defense Forces. About two third of the battalion soldiers are women and their main role is to prevent infiltration on the south borders of Israel.
THE KUDU
Etymology
The name of the animal was imported into English in the 18th century from isiXhosa , via Afrikaans koedoe.
Habitat
Lesser kudus come from the savannas near Acacia and Commophora shrubs. They have to rely on thickets for protection, so they are rarely seen in the open. Their drab brown and striped pelts help to camouflage them in scrub environments.
Behavior
Like many other antelope, male kudus can be found in bachelor groups , but they are more likely to be solitary. Their dominance displays tend not to last long and are generally fairly peaceful, consisting of one male making himself look big by making his hair stand on end. When males do have a face-off, they will lock their horns in a competition to determine the stronger puller; kudus' necks enlarge during the mating season for this reason. Sometimes two competing males are unable to unlock their horns and, if unable to disengage, will die of starvation or dehydration. Males are seen with females only in the mating season, when they join in groups of 5–15 kudus, including offspring. Calves grow very quickly and at six months are fairly independent of their mothers.
A pregnant female will leave the herd to give birth to a single offspring. She will leave the newborn lying hidden for 4–5 weeks while coming back only to nurse it, which is the longest amount of time for any antelope species. Then the calf will start meeting its mother for short periods. At 3 or 4 months , the calf will be with its mother constantly, and at about six months they will permanently join the group.
When threatened, the kudu will often run away rather than fight. Wounded bulls have been known to charge the attacker, hitting the attacker with their sturdy horn base rather than stabbing it. Wounded females can keep running for many miles without stopping to rest for more than a minute. They are great kickers and are capable of breaking a wild dogs or jackal's neck or back. They are good jumpers and can clear a 5-foot fence from a standing start.
Diet
Kudus are browsers and eat leaves and shoots. In dry seasons, they eat wild watermelons and other fruit for the liquid and the natural sugars that they provide. The lesser kudu is less dependent on water sources than the greater kudu.
Predators and threats
Many predators , such as big cats (namely lions and leopards), wild dogs , hyenas and cheetahs , hunt kudu and their young.
Kudus were highly susceptible to the rinderpest virus (now eradicated after a vaccination program in domestic cattle), and many scientist think recurring epidemics of the disease reduced kudu populations in East Africa.
Kudus are highly susceptible to rabies in times of extended drought. They have been known to enter farm houses and other buildings when infected. Infected animals appear tame and have a distinct frothing at the mouth. They are fearless and bulls may sometimes attack humans who get too close to them.
Meat
Kudu meat is similar to venison (deer), with a slight gamey, liver-like flavor. It is a very dry and lean meat, so it needs to be cooked carefully to avoid drying it out and making it difficult to eat. When prepared correctly, it can be very healthy because of its low fat content.
Use in music
A kudu horn, used by Yemenite Jews as a shofar for the holiday of Rosh Hasanah.
A kudu horn is a musical instrument made from the horn of the kudu antelope. A form of it is sometimes used as a shofar in Jewish ceremonies. It is mostly seen in the Western world in its use as a part of the Scouting movement's Wood Badge training program which, when blown, signals the start of a Wood Badge training course or activity.
A horn of this shape, when used by soccer fans, is called kuduzela (a portmanteau of "kudu" and "vuvuzela"). The kudu, "tholo" in the language Setswana , is a tribal totem of the Barolong and Bathaping people of Botswana and South Africa.
Use in sport
In the sport of kudu dung spitting , contestants spit pellets of kudu dung , with the farthest distance reached being the winner. The sport is mostly popular among the Afrikaner community in South Africa, and a world championship is held each year
THE ORYX
Etymology
The term "oryx" comes from the Greek word Ὂρυξ , oryx, for a type of antelope. The Greek plural form is oryges , although oryxes has been established in English.
SPECIES
Arabian oryx
The scimitar oryx is the only oryx with clearly curved horns, ochre neck, and no dark markings on the legs.
The Arabian oryx (Oryx leucoryx) , the smallest species, became extinct in the wild in 1972 from the Arabian Penin sula. It was reintroduced in 1982 in Oman, but poaching has reduced their numbers there. One of the largest populations of Arabian oryx exists on Sir Bani Yas Island in the United Arab Emirates. Additional populations have been reintroduced in Qatar , Bahrain , Israel , Jordan and Saudi Arabia. As of 2011, the total wild population is over 1000, and 6000–7000 are being held in captivity. In 2011, the IUCN downgraded its threat category from Extinct in the Wild to Vulnerable, the first species to have changed back this way.
Scimitar oryx
The scimitar oryx , also called scimitar-horned oryx (Oryx dammah) , of North Africa , is now listed as possibly extinct in the wild. However, unconfirmed surviving populations have been reported in central Niger and Chad, and a semi-wild population currently inhabiting a fenced nature reserve in Tunisia is being expanded for reintroduction to the wild in that country. Several thousand are held in captivity around the world.
East African oryx and gemsbok
The East African oryx resembles the closely related gemsbok , but the latter has an entirely black tail, a black patch at the base of the tail, and more black to the legs and lower flanks.
The East African Oryx (Oryx beisa) inhabits eastern Africa , and the closely related gemsbok (Oryx Gazella) inhabits Southern Africa. Neither is threatened, though the former is considered Near Threatend by the IUCN. The gemsbok is monotypic, and the East African oryx has two subspecies; East African oryx "proper" (O.b beisa) and the fringe-eared oryx (O.b callotis). In the past, both were considered subspecies of the gemsbok.
Between 1969 and 1977, the New Mexico Deparment of Game and Fish intentionally released 93 gemsbok into its state's White Sands Missile Range , and that population is now estimated between 3,000 and 6,000 animals. Within the state of New Mexico, oryxes are classified as "big game" and can be harvested with the proper license, but the quality of the hunt may be affected by military regulation of the missile range.
Ecology
All oryx species prefer near-desert conditions and can survive without water for long periods. They live in herds of up to 600 animals. Newborn calves are able to run with the herd immediately after birth. Both males and females possess permanent horns. The horns are narrow, and straight except in the scimitar oryx, where they curve backwards like a scimitar. The horns are lethal — the oryx has been known to kill lions with them, and oryxes are thus sometimes called the sabre antelope (not to be confused with the sable antelope). The horns also make the animals a prized game trophy, which has led to the near-extinction of the two northern species.
Blue Wildebeest
Taxonomy and naming
The blue wildebeest was first described by English naturalist William John Burchell in 1823 and he gave it the scientific name Connochaetes taurinus. It shares the genus Connochaetes with the black wildebeest (C. gnou) , and is placed in the family B0vidae , ruminant animals with cloven hooves. The generic name Connchaetes derives from the Greek words κόννος, kónnos, "beard", and χαίτη, khaítē, "flowing hair", "mane". The specific name taurinus originates from the Greek word tauros , which means a bull or bullock. The common name "blue wildebeest" refers to the conspicuous, silvery-blue sheen of the coat, while the alternative name "gnu" originates from the name for these animals used by the Khokloi people , a native pastoralist tribe of southwestern Africa.
Though the blue and black wildebeest are currently classified in the same genus, the former was previously placed in a separate Gorgon genus. In a study of the mitotic chromosomes and mtDNA which was undertaken to understand more of the evolutionary relationships between the two species, it was found that the two had a close phylogenetic relationship and had diverged about a million years ago.
Subspecies
C.taurinus has five subspecies:
- C. t. albojubatus (Thomas, 1912; Eastern white-bearded wildebeest), is found in the Gregory Rift Valley (south of the equator). Its range extends from northern Tanzania to central Kenya.
- C. t. cooksoni (Blaine, 1914; Cookson's wildebeest), is restricted to the Luangwa Valley in Zambia. Sometimes these animals may wander into the plateau region of central Malawi.
- C. t. johnstoni (Sclater, 1896; Nyassaland wildebeest), occurs from Mozambique (north of the Zambezi river) to east-central Tanzania. This subspecies is now extinct in Malawi.
- C. t. mearnsi (Heller, 1913; Western white-bearded wildebeest), is found in northern Tanzania and southern Kenya. Its range extends from the west of the Gregory Rift Valley to Speke Bay on Lake Victoria.
- C. t. taurinus (Burchell, 1823; Blue wildebeest, common wildebeest or brindled gnu) is found in southern Africa. Its range extends from Namibia and South Africa to Mozambique (north of the Orange river) and from southwestern Zambia (south of the Zambezi river) to southern Angola.
The blue wildebeest is known to hybridise with its black relative. The differences in social behaviour and habitats have historically prevented interspecific hybridisation, however it may occur when both species are confined within the same area, and the offspring is usually fertile. A study of these hybrid animals at Spioenkop Dam Nature Reserve in South Africa revealed that many had congenital abnormalities relating to their teeth, horns and the Wormian bones of the skull. Another study reported an increase in the size of the hybrid as compared to either of its parents. In some hybrid animals the auditory bullae are highly deformed and in others the radius and ulna are fused.
Genetics and evolution
The diploid number of chromosomes in the blue wildebeest is 58. Chromosomes were studied in a male and a female wildebeest. In the female, all except a pair of very large submetacentric chromosomes were found to be acrocentic. Metaphases were studied in the male's chromosomes, and very large submetacentric chromosomes were found there as well, similar to those in the female both in size and morphology. the rest were acrocentric. The X chromosome is a large acrocentric while the Y chromosome a minute one.
This species of wildebeest seems to have evolved around 2.5 million years ago. The black wildebeest is believed to have diverged from the blue wildebeest to become a distinct species around a million years ago, in the mid to late Pleistocene. Fossil evidence suggests that the blue wildebeest were quite common in the Cradle of Humankind in the past. Apart from eastern Africa, fossils are commonly found in Elandsfontein , Cornelia and Florisbad.
Description
A close view of the blue wildebeest
The blue wildebeest exhibits sexual dimorphism , with males being larger and darker than females. The blue wildebeest is typically between 170–240 cm (67–94 in) in head-and-body length. The average height of the species is 115–145 cm (45–57 in). While males weigh up to 290 kg (640 lb), females seldom exceed 260 kg (570 lb). A characteristic feature is the long, black tail, which is around 60–100 cm (24–39 in) in length. All features and markings of this species are bilaterally symmetrical for both sexes. The average life span is 20 years in the wild and 21 years in captivity. The oldest known captive individual lived for 24.3 years.
Colouration
This broad-shouldered antelope has a muscular, front-heavy appearance, with a distinctive robust muzzle. Young blue wildebeest are born tawny brown, and begin to take on their adult colouration at the age of two months. The adults' hues range from a deep slate or bluish gray to light gray or even grayish-brown. The back and flanks are slightly lighter than the ventral surface and underparts. Dark brown vertical stripes mark the area between the neck and the back of the ribcage, thus giving it the name "brindled gnu". The manes of both sexes appear long, stiff, thick and jet black, the same colour as the tail and face as well. While the manes of the western and eastern white-bearded wildebeest are lank, those of the Nyassaland wildebeest and common wildebeest stick up. Scent glands, which secrete a clear oil, are present in the forefeet and are larger in males than females.
In terms of skull length, the smallest subspecies of the blue wildebeest is the western white-bearded wildebeest. It is also the darkest subspecies, the eastern white-bearded wildebeest being the lightest race. Both these subspecies possess a creamy white beard, whereas the beard is black in both the Nyassaland wildebeest and the common wildebeest. The longest muzzles are found in the Nyassaland wildebeest, and the shortest in female western white-bearded wildebeest.
Horns
Both sexes possess a pair of large horns which are shaped like parentheses. These extend outward to the side, and then curve upward and inward. In the males, the horns can be 83 cm (33 in) long, while the horns of the females are 30–40 cm (12–16 in) long. Despite being an antelope, the blue wildebeest possesses various bovine characteristics. For instance, the horns resemble those of the female African buffalo. Further, the heavy build and disproportionately large forequarters give it a bovine appearance.
Diseases and parasites
While rinderpest is probably the most serious disease from which the blue wildebeest suffers, it is also susceptible to foot-and-mouth disease, anthrax, sarcoptic mange and hoof gangrene. The herpesvirus was first isolated from the blue wildebeest in 1960 by veterinary scientist Walter Plowright. Although the causes of death will vary from year to year, in one drought in Botswana, young calves and aged females were the most likely to die. On another occasion it was estimated that 47% of deaths were caused by disease, 37% were due to predation and the remainder were the result of accidents.
The animal can be host to a number of different parasites. In one study, blue wildebeest were found to be hosts to thirteen species of nematode, one trematode, larvae of five oestrid flies, three species of lice, seven ixodid tick species, one mite and the larvae of a tongue worm. Of these, most were more prevalent at some times of the year than others. Generally, the larvae of Gedoelstica and Oestrus occur in the nasal passages and respiratory cavities of the blue wildebeest, and sometimes migrate to the brain. Compared to some other bovids, blue wildebeest are resistant to infestations by several species of tick.
Ecology and behaviour
Plains zebra and blue wildebeest grazing at Ngorongoro Crater
The blue wildebeest is mostly active during the morning and the late afternoon, with the hottest hours of the day being spent in rest. These extremely agile and wary animals can run at speeds of up to 80 km/h (50 mph), waving their tails and tossing their heads. An analysis of the activity of blue wildebeest at the Serengeti national Park showed that the animals devoted over half of their total time to rest, 33% to grazing, 12% to moving about (mostly walking) and a little to social interactions. However, there were variations among different age and sex groups.
The wildebeest usually rest close to others of their kind and move about in loose aggregations. Males form bachelor herds, and these can be distinguished from juvenile groups by the lower amount of activity and the spacing between the animals. Around 90% of the male calves join the bachelor herds before the next mating season. Bulls become territorial at the age of four or five years, and become very noisy (most notably in the western white-beared wildebeest) and active. The bulls tolerate being close to each other and a square kilometre of plain can accommodate 270 bulls. Most territories are of a temporary nature and fewer than a half of the male population hold permanent territories. In general, blue wildebeest rest in groups of a few to thousands at night, with a minimum distance of 1–2 m (3.3–6.6 ft) between individuals (though mothers and calves may remain in contact). They are a major prey item for lions, hyenas, and crocodiles.
Bulls mark the boundaries of their territories with heaps of dung and with secretions from their scent glands. The territories are advertised by their behaviour as well as by the physical marking. Body language used by a territorial male includes standing tall with an erect posture, profuse ground pawing and horning, frequent defecation, rolling and bellowing, the sound "ga-noo" being produced. When competing over territory, males grunt loudly, paw the ground, make thrusting motion with their horns, and perform other displays of aggression.
Diet
The blue wildebeest is a herbivore, feeding primarily on the short grasses which commonly grow on light, and alkaline soils that are found in savanna grasslands and on plains. The animal's broad mouth is adapted for eating large quantities of short grass and it feeds both during the day and night. When grass is scarce, it will also eat the foliage of shrubs and trees. Wildebeest commonly associate with plains zebras as the latter eat the upper, less nutritious grass canopy, exposing the lower, greener material which the wildebeest prefer. Whenever possible, the wildebeest likes to drink twice daily and due to its regular requirement for water, it usually inhabits moist grasslands and areas with available water sources. Despite this, it can also survive in the arid Kalahari desert, where it obtains sufficient water from melons and water-storing roots and tubers.
In a study of the dietary habits of the wildebeest, the animals were found to be feeding on the three dominant grasses of the area, namely : Themeda triandra, Digitaria macroblephara and Penisetum mezianum. The time spent grazing increased by about 100% during the dry season. Though the choice of diet remained the same in both the dry and the wet season, the animals were more selective during the latter.
Reproduction
Blue wildebeest fighting for dominance
Male blue wildebeest become sexually mature at about two years of age while females can conceive at sixteen months if adequately nourished. Nevertheless, most females do not start to breed until a year later. The mating season, which lasts for about three weeks, coincides with the end of the rainy season. This means that the animals are in good condition, having been feeding on highly nutritious new grass growth, and the conception rate is often as high as 95%. The mating season, or rut, typically begins on the night of a full moon, suggesting that the lunar cycle influences breeding. At this time, testosterone production peaks in males, resulting in increased calling and territorial behaviour. The activities of these sexually excited males may also stimulate female to come into estrus.
As they stake out their territories and compete for females, males exhibit rivalry. When they clash, they face up to each other with bent knees and exchange horn thrusts. Elaborate individual displays are made during their rivalry and they may bellow, snort and dig their horns into the ground. Once dominance has been established, each male attempts to lure the female into his domain. During courtship, urination and low-stretch are common activities and the male soon attempts to mount the female. A receptive female holds her tail to one side and stands still while copulation takes place. Matings may be repeated several times and may take place twice or more times within a minute. The male neither eats nor rests when a female is present in his territory and during this time, the female keeps close to the male, often rubbing her head on his torso and sniffing his penis. While in season, a female may visit several territories and mate with several different males.
The gestation period is about eight and a half months and between 80 and 90% of the calves are born within a three-week time period. Female wildebeest give birth in the middle of a herd rather than alone, and typically in the middle of the day. This allows time for the newborn to become steady on its feet before night falls and the predators become more active. Calves weigh about 19 kg (42 lb) at birth, and can usually stand on their own within a few minutes of birth. To escape predation, calves remain close to their mothers for a significant time, and may continue suckling until the next year's calf is nearly due. Some calves leave their mother at about eight months and form herds with other juveniles. In large female herds, 80% of the wildebeest offspring survive the first month, compared to a 50% survival rate in smaller herds.
Distribution and habitat
Blue wildebeest inhabits places where water is available.
The blue wildebeest is native to Kenya, Tanzania, Botswana, Zambia, Zimbabwe, Mozambique, South Africa, Swaziland and Angola. Today it is extinct in Malawi, but has been successfully reintroduced into Namibia.
Blue wildebeest are mainly found in short grass plains bordering bush-covered acacia savannas in southern and eastern Africa, thriving in areas that are neither too wet nor too arid. They can be found in habitats that vary from overgrazed areas with dense bush to open woodland floodplains. Trees such as Brachystegia and Combretum are common in these areas. Blue wildebeest can tolerate arid regions as long as a potable water supply is available, normally within about 15–25 km (9.3–15.5 mi) distance. The southern limit of the blue wildebeest stops at the Orange river, while the western limit is bounded by Lake Victoria and Mt Kenya. The range does not include montane or temperate grasslands. These wildebeest are rarely found at altitudes in excess of 1,800–2,100 m (5,900–6,900 ft). With the exception of a small population of Cookson's wildebeest that occurs in the Luangwa Valley (Zambia), the wildebeest is absent in the wetter parts of the southern savanna country, and particularly is not present in miombo woodlands.
Each year, some East African populations of blue wildebeest take part in a long-distance migration, seemingly timed to coincide with the annual pattern of rainfall and grass growth. The timing of the migration in both directions can vary considerably from year to year. At the end of the rainy season, they migrate to dry-season areas in response to a lack of drinking water. When the rainy season begins again a few months later, the animals trek back to their wet-season range.
Threats and conservation
A pair of blue wildebeest in Royal Burgers' Zoo (Netherlands)
The blue wildebeest is preyed on by lions, leopards, African wild dogs and hyenas and predation is the main cause of death. They are also prone to outbreaks of disease which may also lead to a decline in numbers. Major human-related factors affecting populations include large-scale deforestation, the drying up of water sources, the expansion of settlements and poaching. Diseases of domestic cattle such as sleeping sickness can be transmitted to the animals and take their toll. The erection of fences that interrupt traditional migratory routes between wet and dry-season ranges have resulted in mass death events when the animals become cut off from water sources and the areas of better grazing they are seeking during droughts. A study of the factors influencing wildebeest populations in the Maasai Mara ecosystem revealed that the populations had undergone a drastic decline of around 80% from about 119,000 individuals in 1977 to around 22,000 twenty years later. The major cause of this was thought to be the expansion of agriculture, which led to the loss of wet season grazing and the traditional calving and breeding ranges.
The total number of blue wildebeest is estimated to be around 1,550,000. The population trend overall is stable and the numbers in the Serengeti national Park (Tanzania) have increased to about 1,300,000. The population density ranges from 0.15/km2 in Hwange and Etosha National Parks to 35/km2 in Ngorongoro Crater and Serengeti National Park where they are most plentiful. Blue wildebeest have also been introduced into a number of private game farms, reserves and conservancy areas. For these reasons, the International Union for Conservation of Nature (IUCN) rates the blue wildebeest as being of Least Concern. However, the numbers of the eastern white-bearded wildebeest (C. t. albojubatus) have seen a steep decline in numbers to a current level of probably 6,000 to 8,000 animals and this is causing some concern.
Uses and interaction with humans
As one of the major herbivores of southern and eastern Africa, the blue wildebeest plays an important role in the ecosystem and is a main prey item for large predators such as the lion. It is one of the animals that draws tourists to the area to observe big game and as such it is of major economic importance to the region. Traditionally blue wildebeest have been hunted for their hides and meat, the skin making good quality leather though the flesh is coarse, dry and rather hard.
However, blue wildebeest can also affect human beings negatively. They can compete with domestic livestock for grazing and water and can transmit fatal diseases like rinderpest to cattle and cause epidemics among animals. They can also spread ticks, lungworms, tapeworms, flies and paramphistome flukes.
An ancient carved slab of slate depicting an animal very similar to the blue wildebeest has been discovered. Dating back to around 3000 BC, it was found in Hierkonopolis (Nekhen), which used to be the religious and political capital of Upper Egypt at that time. This may be evidence that the animal used to occur in North Africa and was associated with the ancient Egyptians.
Black Wildebeest
Taxonomy and evolution
The scientific name of the black wildebeest is Connochaetes gnou. The animal is placed in the genus Connochaetes and family Bovidae and was First described by the German zoologist, Eberhard August Wilhelm von Zimmermann in 1780. He based his description on an article written by natural philosopher Jean-Nicolas-Sebastien allmand in 1776. The generic name Connochaetes derives from the Greek words κόννος, kónnos, "beard", and χαίτη, khaítē, "flowing hair", "mane". The specific name "gnou" originates from the Khoikhoi name for these animals, gnou. The common name "gnu" is also said to have originated from the Hottntot name T'gnu, which refers to the repeated calls of "ge-nu" by the bull in the mating season. The black wildebeest was first discovered in the northern part of South Africa in the 1800s.
The black wildebeest is currently included in the same genus as the blue wildebeest (Connochaetes taurinus). This has not always been the case and at one time the latter was placed under a separate genus of its own, Gorgon. The black wildebeest lineage seems to have diverged from the blue wildebeest in the mid to late Pleistocene, and became a distinct species around a million years ago. This evolution is quite recent on a geologic time scale.
Features necessary for defending a territory such as the horns and broad-based skull of the modern black wildebeest, have been found in their fossil ancestors. The earliest known fossil remains are in sedimentary rock in Cornelia in the Orange Free State and date back about eight hundred thousand years. Fossils have also been reported from the Vaal River deposits, though it is unclear whether or not they are as ancient as those found in Cornelia. Horns of the black wildebeest have been found in sand dunes near Hermanus in South Africa. This is far beyond the recorded range of the species and it has been suggested that these animals may have migrated to that region from the Karoo.
Hybrids
The black wildebeest is known to hybridise with its taxonomically close relative, the blue wildebeest. Male black wildebeest have been reported to mate with female blue wildebeest and vice versa. The differences in social behavior and habitats have historically prevented interspecific hybridization between the species, however hybridization may occur when they are both confined within the same area. The resulting offspring is usually fertile. A study of these hybrid animals at Spioenko Dam Nature Reserve in South Africa revealed that many had disadvantageous abnormalities relating to their teeth, horns and the wormian bones in the skull. Another study reported an increase in the size of the hybrid as compared to either of its parents. In some animals the auditory bullae are highly deformed and in others the radius and ulna are fused.
Description
The black wildebeest has horns that curve forward.
Black wildebeest are sexually dimorphic, with females being smaller in size and more slender than males. The head-and-body length is typically between 170 and 220 cm (67 and 87 in). Males reach approximately 111 to 121 cm (44 to 48 in) at the shoulder, while females reach 106 to 116 cm (42 to 46 in). Males typically weigh 140 to 157 kg (309 to 346 lb.) and females 110 to 122 kg (243 to 269 lb.). A distinguishing feature in both sexes is the tail, which is long and similar to that of a horse. Its bright-white colour gives this animal the vernacular name of "white-tailed gnu", and also distinguishes it from the blue wildebeest, which has a black tail. The length of the tail ranges from 80 to 100 cm (31 to 39 in).
The black wildebeest has a dark brown or black coat which is slightly paler in summer and coarser and shaggier in the winter. Calves are born with shaggy, fawn-coloured fur. Males are darker than females. They have bushy and dark-tipped manes that, as in the blue wildebeest, stick up from the back of the neck. The hairs which compose this are white or cream-coloured with dark tips. On its muzzle and under its jaw it has black bristly hair. It also has long, dark-coloured hair between its forelegs and under its belly. Other physical features include a thick neck, a plain back, and rather small and beady eyes.
Both sexes have strong horns that curve forward, resembling hooks and are up to 78 cm (31 in) long. The horns have a broad base in mature males, and are flattened to form a protective shield. In females, the horns are both shorter and narrower. They become fully developed in females in the third year, while it is not before the age of four or five that horns are fully grown in males. The black wildebeest normally has 13 thoracic vertebrae, though specimens with 14 have been reported, and this species shows a tendency for the thoracic region to become elongated. There are scent glands that secrete a glutinous substance in front of the eyes, under the hair tufts and on the forefeet. Females have two nipples. Apart from the difference in the appearance of the tail, the two species of wildebeest also differ in size and colour, with the black being smaller and darker than the blue.
The black wildebeest can maintain its body temperature within a small range in spite of large fluctuations in external temperatures. It shows well-developed orientation behavior towards solar radiation which helps it thrive in hot, and often shadeless, habitats. The erythrocyte count is high at birth and increases till the age of two to three months, while in contrast, the leucocyte count is low at birth and falls throughout the animal's life. The neutrophil count is high at all ages. The hematocrit and hemoglobin content decreases till twenty to thirty days after birth. There is a peak in the content of all these homological parameters at the age of two to three months, after which the readings gradually decline, reaching their lowest values in the oldest individuals. The presence of fast-twitch fibres and the ability of the muscles to use large amounts of oxygen help explain the rapid running speed of the black wildebeest and its high resistance to fatigue. Individuals may live for about twenty years.
Diseases and parasites
The black wildebeest is particularly susceptible to anthrax, and rare and widely scattered outbreaks have been recorded and have proved deadly. Ataxia related to myelopathy and low copper concentrations in the liver have also been seen in the black wildebeest. Heart water (Ehrlichia ruminantium) is a tick-borne rickettsia disease that affects the black wildebeest and, as the blue wildebeest is fatally affected by rinderpest and foot-and-mouth disease, it is believed that the black wildebeest is also likely to be susceptible to these. Malignant catarrhal fever is a fatal disease of domestic cattle caused by a gammaherpesvirus. It seems that, like the blue wildebeest, the black wildebeest acts as a reservoir for the virus and that all animals are carriers, being persistently infected but showing no symptoms. The virus is transmitted from mother to calf during the gestation period or soon after birth.
Black wildebeest act as hosts to a number of external and internal parasites. A study of the animal in Karroid Mountainveld (Eastern Cape Province, South Africa) revealed the presence of all the larval stages of the nasal bot flies Oestrus variolosus and Gedoelstia hassleri. The first instar larvae of G hassleri were found in large numbers on the dura mater of wildebeest calves, especially between June and August, and these later migrated to the nasal passages. Repeated outbreaks of mange (scab) have led to large-scale extinctions. The first study of the protozoa in blue and black wildebeest showed the presence of 23 protozoan species in the rumen, with Diplodinium bubalidis and Ostracodinium damaliscus common in all the animals.
Ecology and behavior
Black wildebeest can run at speeds of up to 80 km/h (50 mph).
Black wildebeest are mainly active during the early morning and late afternoon preferring to rest during the hottest part of the day. The animals can run at speeds of 80 km/h (50 mph). When a person approaches a herd to within a few hundred metres, the wildebeest snort and run a short distance before stopping and looking back, repeating this behavior if further approached. They communicate with each other using pheromones detected by flehmen and several forms of vocal communication. One of these is a metallic snort or an echoing "hick", that can be heard up to 1500 meters (1 mile) away. They are preyed on by animals like lion, spotted hyena, Cape hunting dog, leopard, cheetah and crocodile. Of these the calves are targeted manly by the hyenas, while lions attack the adults.
The black wildebeest is a gregarious animal with a complex social structure comprising three distinct groups: firstly, the female herds, consisting of adult females and their young; secondly, the bachelor herds, consisting only of yearlings and older males; thirdly, the territorial bulls. The number of females per herd is variable, generally ranging from 14 to 32, but is highest in the densest populations and also increases with forage density. There is a strong attachment among members of the female herd, many of whom are related to each other. Large herds often get divided into smaller groups. While small calves stay with their mothers, the older ones form groups of their own within the herd. These herds have a social hierarchy, and the females are rather aggressive towards others trying to join the group. Young males are generally repelled by their mothers before the calving season starts. Separation of a young calf from its mother can be a major cause of calf mortality. While some male yearlings stay within the female herd, the others join a bachelor herd. These are usually loose associations and, unlike the female herds, the individuals are not much attached to each other. Another difference between the female and bachelor herds is the lesser aggression on the part of the males. These bachelor herds move widely in the available habitat and act as a refuge for males that have been unsuccessful as territorial bulls, and also as a reserve for future breeding males.
Mature bulls, generally more than four years old, set up their own territories through which female herds often pass. These territories are maintained throughout the year, with animals usually separated by a distance of about 100–400 m (330–1,310 ft.), but this can vary according to the quality of the habitat. In favorable conditions, this distance is as little as 9 m (30 ft.), but can be as large as 1,600 m (5,200 ft.) in poor habitat. Each bull has a patch of ground in the center of his territory in which he regularly drops dung, and in which he performs acts of display. These include urinating, scraping, pawing and rolling on the ground and thumping it with his horns - all of which demonstrate his prowess to other bulls. An encounter between two bulls involves elaborate rituals. Estes coined the term "Challenge Ritual" to describe this behavior for the blue wildebeest, but this is also applicable to the black wildebeest, owing to the close similarity in the behavior in both species. The bulls approach each other with their heads lowered, resembling a grazing position (sometimes actually grazing). This is usually followed by movements like standing in a reverse-parallel position, in which one male urinates and the opponent smells and performs freshmen, after which they may reverse the procedure. During this ritual or afterwards the two can toss their horns at each other, circle one another, or even look away. Then begins the fight, which may be of low intensity (consisting of interlocking the horns and pushing each other in a standing position) or high intensity (consisting of their dropping to their knees and straining against each other powerfully, trying to remain in contact while their foreheads are nearly touching the ground). Threat displays like shaking the head may also take place.
Diet
The black wildebeest is primarily a grazer.
Black wildebeest are predominantly grazers, preferring short grasses but also feeding on other herbs and shrubs, especially when grass is scarce. Shrubs can comprise as much as 37% of the diet but grasses normally forms more than 90%. Water is essential, though they can exist without drinking water everyday. The herds graze either in line or in loose groups, usually walking in single file when moving about. They are often accompanied by cattle egrets, which pick out and consume the insects hidden in their coats or disturbed by their movements.
Before the arrival of Europeans in the area, wildebeest used to roam widely, probably in relation to the arrival of the rains and the availability of good forage. They never made such extensive migrations as the blue wildebeest but at one time, they used to cross the Drakensberg Range, moving eastwards in autumn, searching for good pastures. Then they returned to the Highveld’s in the spring and moved towards the west, where sweet potato and Karoo vegetation were abundant. They also moved from north to south as the sour grass found north of the Vaal River matured and became unpalatable, the wildebeest only consuming young shoots of sour grass. Nowadays, almost all black wildebeest are in reserves or on farms and the extent of their movements is limited.
In a study of the feeding activities of a number of female black wildebeest living in a shadeless habitat, it was found that they fed mostly at night. They were observed at regular intervals over a period of one year and it was observed that with an increase in temperature, the number of wildebeest feeding at night also increased. During cool weather they lay down to rest but in hotter conditions they rested while standing up.
Reproduction
Male black wildebeest reach sexual maturity at the age of three years but may mature at a younger age in captivity. Females first come into season and breed as yearlings or as two-year-olds. They breed only once in a year.
A dominant male black wildebeest will have a harem of females and will not allow other males to mate with them. The breeding season occurs at the end of the rainy season and lasts a few weeks between February and April. When one of his females comes into oestrus the male concentrates on her and mates with her several times. Sexual behavior by the male at this time includes stretching low, ears down, sniffing of the female's vulva, performing ritual urination and touching his chin to the female's rump. At the same time, the female keeps her tail upwards (sometimes vertically) or swishes it across the face of the male. The pair usually separates after copulation, but the female occasionally follows her mate afterwards, touching his rump with her snout. During the breeding season, the male loses condition as he spends little time grazing. Males are known to mount other males.
The gestational period lasts for about eight and a half months, after which a single calf is born. Females in labour do not move away from the female herd and repeatedly lie down and get up again. Births normally take place in areas with short grass when the cow is in the lying position. She stands up immediately afterwards which causes the umbilical cord to break, vigorously licks the calf and chews on the afterbirth. In spite of regional variations, around 80% of the females give birth to their calves within a period of two to three weeks after the onset of the rainy season - from mid-November to the end of December. Seasonal breeding has also been reported among wildebeest in captivity in European zoos. Twin births have not been reported.
The calf has a tawny, shaggy coat and weighs about 11 kilograms (24 lb.). By the end of the fourth week, the four incisors have fully emerged and about the same time, two knob-like structures, the horn buds, appear on the head. These later develop into horns which reach a length of 200–250 mm (8–10 in) by the fifth month and are well developed by the eighth month. The calf is able to stand and run shortly after birth, a period of great danger for animals in the wild. It is fed by its lactating mother for six to eight months, begins nibbling on grass blades at four weeks and remains with her until her next calf is born a year later.
Distribution and habitat
The black wildebeest is native to southern Africa. Its historical range included South Africa, Swaziland and Lesotho, but in the latter two countries it was hunted to extinction in the 19th century. It has now been reintroduced to them and also introduced to Namibia where it has become well established.
The black wildebeest inhabits open plains, grasslands and Karoo shrub lands in both steep mountainous regions and lower undulating hills. The altitudes in these areas varies from 1,350–2,150 m (4,430–7,050 ft.). the herds are often migratory or nomadic, otherwise they may have regular home ranges of 1 km2 (11,000,000 sq. ft.). Female herds roam in home ranges around 250 acres (100 ha; 0.39 sq.) in size. In the past, black wildebeest occurred in the Highveld temperate grasslands during the dry winter season and the arid Karoo region during the rains. However, as a result of massive hunting of the animal for its hide, they vanished from their historical range, and are now largely limited to game farms and protected reserves in southern Africa. In most reserves, the black wildebeest shares its habitat with the blesbok and the springbok.
Threats and conservation
Where it lives alongside the blue wildebeest, the two species can hybridise, and this is regarded as a potential threat to the maintenance of the species. The black wildebeest was once very numerous and was present in southern Africa in vast herds but by the end of the nineteenth century, it had nearly been hunted to extinction and fewer than 600 animals remained. A small number of individuals was still present in game reserves and at zoos and it is from these that the population was rescued.
There are now believed to be more than 18,000 individuals, 7,000 of which are in Namibia, outside its natural range, and where it is farmed. Around 80% of the wildebeest occur in private areas, while the other 20% are confined in protected areas. The population is now trending upward (particularly on private land) and for this reason the International Union for Conservation of Nature (IUCN), in its Red List of Threatened Species, rates the black wildebeest as being of "Least Concern". Its introduction into Namibia has been a success and numbers have increased substantially there from 150 in 1982 to 7,000 in 1992.
Uses and interaction with humans
The black wildebeest is depicted on the coat of arms of the Province of Natal in South Africa. Over the years the South African authorities have issued stamps displaying the animal and the South African Mint has struck a five rand coin with a prancing black wildebeest.
Though they are not present in their natural habitat in such large numbers today, black wildebeest were at one time the main herbivores in the ecosystem and a main prey item for large predators such as the lion. Nowadays they are economically important for human beings as they are a major tourist attraction as well as providing animal products such as leather and meat. The hide makes good quality leather and the flesh is coarse, dry and rather hard. Wildebeest meat is dried to make biltong, an important part of South African cuisine. The meat of females is tenderer than that of males, and is at its best during the autumn season. The wildebeest can provide ten times as much meat as the Thomson's gazelle. The silky, flowing tail is used to make fly-whisks or "chowries".
However, black wildebeest can also affect human beings negatively. Wild individuals can be competitors of commercial livestock, and can transmit fatal diseases like rinderpest and cause epidemics among animals, particularly domestic cattle. They can also spread ticks, lungworms, tapeworms, flies and paramphistome flukes.
The Springbok
Appearance
Springboks are slender, long-necked antelopes, with a total length of 150 to 195 cm (59 to 77 in), and horns present in both sexes. Adults are between 70 and 90 cm (28 and 35 in) tall at the shoulder, depending on weight and gender; they weigh between 30 and 44 kg (66 and 97 lb) for the females and 33 and 48 kg (73 and 106 lb) for the males. The tail is 15 to 30 centimetres (5.9 to 11.8 in) long.
Their colouring consists of a pattern of white, reddish/tan and dark brown. Their backs are tan-coloured and they are white beneath, with a dark brown stripe extending along each side from the shoulder to inside the thigh. The face is white in adults, with a dark patch on the forehead, and a stripe running from just above the eyes to the corner of the mouth. The hooves and horns are black, and the tail is white with a black tuft at the tip.
Rams are slightly larger than ewes, and have thick horns; the ewes tend to have skinnier legs and longer, more frail horns. The horns are, however, of similar shape in both sexes, with a hook-like tip that curves inwards, and a series of rings along their length. The average horn length for both genders is 35 cm (14 in), with the record being a female with horns measuring 49.21 centimetres (19.37 in). Springbok footprints are narrow and sharp, and are 5.5 cm (2.2 in) long. springbok are distinguished from gazelle in that they only have two premolar teeth in each side of each jaw, instead of three, and therefore a total of twenty eight teeth, rather than thirty.
There are three variations in the color of springbok pelage. In addition to the normal-coloured springboks there are also black and white morphs. Although born jet black, adult "black" springboks primarily have two shades of chocolate-brown and a white marking on the face. White springboks are predominantly white with a very light brown coloured side stripe.
Distribution and habitat
Springbok inhabit the dry inland areas of south and southwestern Africa. Their range extends from the northwestern part of South Africa through the Kalahari desert into Namibia and Botswana. Springbok occur in numbers of up to 2,500,000 in South Africa; it is the most plentiful antelope. They used to be very common, forming some of the largest herds of mammals ever documented, but their numbers have diminished significantly since the 19th century due to hunting and fences from farms blocking their migratory routes.
In South Africa, springbok inhabit the vast grasslands of the Free State and the open shrublands of the greater and smaller Karoo. They inhabit most of Namibia – the grasslands of the south, the Kalahari desert to the east, and the dry riverbeds of the northern bushveld of the Windhoek region, as well as the harsh Namib Desert on the west coast. In Botswana, they mostly live in the Kalahari desert in the southwestern and central parts of the country.
Three subspecies are recognised:
- Antidorcas marsupialis marsupialis - South Africa
- Antidorcas marsupialis angolensis - northern Namibia, southern coastal region of Angola
- Antidorcas marsupialis hofmeyri - southern and central Namibia, Botswana
Springbok are mixed feeders, switching between grazing and browsing seasonally. When grasses are fresh, they mostly graze. At other times, they browse on shrubs and succulents. Springbok can meet their water needs from the food they eat, and survive without drinking water through dry season, or even over years. Reportedly, in extreme cases, they do not drink any water over the course of their lives. Springbok may accomplish this by selecting flowers, seeds, and leaves of shrubs before dawn, when these foods are most succulent. Springbok gather together in the wet seasons and spread out during the dry season, an unusual trait among African animals. In places such as Etosha, springbok can and do seek out water bodies when they are available. Examples of food items eaten by springbok are grasses, such as Themeda triandra, and succulent plants, such as Lampranthus.
Behavior
Springbok are mainly active around dawn and dusk, although they may feed through the day in colder weather, or through the night at particularly hot times of the year. During the summer, they sleep in the shade of trees or bushes, although they often bed down in the open when the weather is cooler.
The social structure of the springbok is similar to the Thomson's gazelle. Bachelor males and females form separate herds, although mixed sex herds are also common, with a roughly 3:1 female:male ratio. These groups are normally kept separate by territorial males, which round up female herds that enter their territories and keep out the bachelors. Females may leave the herds solitarily or in groups to give birth. Mothers and fawns may gather in nursery herds separate from harem and bachelor herds. After weaning, female offspring stay with their mothers until a new young is born, while males join bachelor groups.
Outside of the rut, mixed sex herds can range from as few as three to as many as 180 individuals, while all-male bachelor herds are of typically no more than fifty individuals. Harem and nursery herds are much smaller, typically including no more than ten individuals. The Dutch/Afrikaans term trekbokken refers to the large-scale migration of herds of springbok seen roaming the country during the early pioneer days of South Africa before farm fences were erected. Millions of migrating springbok formed herds hundreds of kilometres long that could take several days to pass a town. These are the largest herds of mammals ever witnessed.
Springbok often go into bouts of repeated high leaps of up to 2 m (6 ft 7 in) into the air in a practice known as "pronking" (Afrikaans and Dutch: pronk, to show off) or "stotting". While pronking, the Springbok repeatedly leaps into the air in a particular stiff-legged posture, with its back bowed and the white fan lifted. While the exact cause of this behaviour is unknown, springbok exhibit this activity when they are nervous or otherwise excited. One theory is pronking is meant to indicate to predators that they have been spotted. Another is the springbok show off their individual strength and fitness so the predator will go for another (presumably weaker) member of the group. Another opinion is springbok and other similar antelopes do this to spray scent secreted from a gland near the heel.
Springbok make occasional low-pitched bellows as a greeting and high-pitched snorts when alarmed, but are otherwise relatively quiet animals.
Reproduction
Springbok mate year-round, although females may be more likely to enter oestrus during the rainy season, when food is more plentiful. During the rut, males establish territories, ranging from 10 to 70 hectares (25 to 173 acres), which they mark by urinating and depositing large piles of dung. Males in neighbouring territories frequently fight for access to females, which they do by twisting and levering at each other with their horns, interspersed with occasional stabbing attacks. Females wander between the territories of different males, rather than remaining in a single one for long periods of time. When one approaches a territorial male, the male holds his head and tail out horizontally, lowers his horns and makes a loud grunting noise to attract her. The male then urinates and sniffs the female's perineum. If the female is receptive, she also urinates, and the male makes a flehmen gesture, and taps her leg until the female either leaves or permits him to mate.
Gestation lasts 168 days, and results in the birth of a single calf, or, rarely, twins. The young weigh from 3.8 to 5 kg (8.4 to 11.0 lb) at birth, and are initially left under shelter, such as a bush, while the female feeds elsewhere. Mother and calf rejoin the herd about three to four weeks after birth, and the young are weaned at five to six months. Springbok typically leave their mother when she next gives birth, by which time they are normally about six to twelve months old. Females are sexually mature at seven months, but rarely mate during their first year, while males are mature at two years of age. Springbok live for up to ten years.
Predators
Leopards, cheetahs, hyenas, and lions are the springbok's primary predators. A study in the Etosha National Park found that springboks are the most common prey species for lions, accounting for nearly seventy percent of the hunts. Pythons occasionally take springboks; black-backed jackol, carcals, and eagles often take springbok lambs.
Other herbivores
It shares its range with many other herbivores, such as the gemsbok, african bush elephant, blue wildebeest, plains zebra, and blesbok. It is sympatric with the impala only in certain corners of its range, such as Etosha national Park and the Pilanesberg area.
Evolution
Fossil springbok are known from the Pliocene, and appear to have first evolved about three million years ago, from a gazelle-like ancestor. Three fossil species have been identified, in addition to the extant form, and appear to have been widespread across Africa. Two of these, Antidorcas bondi and A. australis, became extinct during the early Holocene, about 7,000 years ago. The third species, A. recki, probably gave rise to the living form during the Pleistocene, about 0.1 million years ago.
Relationship with humans
Since prehistory, the springbok was hunted by primitive man using stone tools. Up to the present, springbok are hunted as game throughout Namibia, Botswana and South Africa because of their beautiful coats, and because they are very common and easy to support on farms with very low rainfall, which means they are cheap to hunt, as well. The export of springbok skins, mainly from Namibia and South Africa, is also a booming industry. The meat is a prized fare.
Springbok are one of the few antelope species considered to have an expanding population.
National symbol
The springbok was a national symbol of South Africa under white minority rule (including a significant period prior to the establishment of apartheid). It was adopted as a nickname or mascot by a number of South African sports teams, most famously by the national rugby union team. It appeared on the emblems of the South African Air Force, the logo of South African Airways (for which it remains their radio callsign), the reverse of the Krugerrand, and the coat of arms of South Africa. It also featured as the logo of 'South Africa's Own Car', the Ranger, in the early 1970s.
The former South African prime minister and architect of apartheid, Hendrik Frensch verwoerd, had a dream to change the then-current flag of South Africa, remove the three small flags in its center (he objected especially to the British Union Flag being there) and replace them with a leaping springbok antelope over a wreath of six proteas. This proposal aroused too much controversy to be implemented.
The springbok is currently the national animal of South Africa.
After the demise of apartheid, the African National Congress government decreed that South African sporting teams were to be known as the Proteas after the national flower of South Africa. The national rugby team still maintains the name Springboks, and are affectionately known by their supporters as the Boks. The emblem issue occasionally resurfaces and leads to some political controversy. It is recognised and supported by most South Africans, however.
During the Second Boer War, a Boer force attempting to sneak up on the royal Canadian Dragoons was defeated after their movements startled the nearby springbok, thus alerting the Canadian sentries, which is why the Dragoons have the springbok as their cap badge and as their mascot.
The Impala
Taxonomy and naming
The scientific name of the impala is Aepyceros melampus. It is the type species of the genus Aepyceros and belongs to the family Bovidae. It was first described by German zoologist Martin Hinrich Carl Lichtenstein in 1812. The vernacular name "impala" comes from the Zulu language meaning "gazelle". The scientific name is derived from Greek words αιπος aipos ("high"), κερος ceros ("horn") and melas ("black"), pous ("foot").
Due to its close affinity to some species of gazelles, the kob and reedbucks, taxonomists had placed the impala in the same tribe as these alcelaphines. Its resemblance to the hartebeest led palaeontologist Elisabeeth Verba to consider the impala as a sister clade to the alcelaphines, and Aepyceros was included under subfamily Alcelaphinae in 1985. However, the impala was subsequently placed in its own tribe, Aepycerotini, in 1992, which has been elevated to subfamily status.
Up to six subspecies have been described, although only two are usually recognized, supported by mitochondrial DNA analysis. These are the common (A.m. melampus) and the black-faced (A.m. petersi) impala. While the former is abundant throughout southern and eastern Africa, the latter is restricted to southwestern Africa. Both subspecies show much genetic differntiation, and no hybrids are known. Several fossil species have been found, including A. datoadeni from the Pliocene of Ethiopia.
A study by Verba revealed that while the common alcelaphine ancestor has diverged at least 18 times into various morphologically different forms of hartebeest and wildebeest, the impala has continued in its basic form for at least five million years. The oldest fossil discovered suggests its ancient ancestors were slightly smaller than the modern form, but otherwise similar in all respects to the latter. Even the two subspecies have only a few differences between them. This implies that the impala is perfectly adapted to its environment. Its gregarious nature, variety in diet, high population growth, defense against ticks and cooperation with oxpeckers who feed on ticks are some of the traits suggested as preventing major changes in morphology and behavior.
Physical description
It is a sexually dimorphic antelope; only males are horned, and they are noticeably larger than the females. The head-and-body length for the species as a whole is typically between 120–160 cm (47–63 in). Males reach approximately 75–92 cm (30–36 in) at the shoulder, while females reach 70–85 cm (28–33 in). Males typically weigh 53–76 kg (117–168 lb.) and females 40–53 kg (88–117 lb.). The tail is 30–45 cm (12–18 in) long. The impala is comparable in size to the kob.
The coat is a glossy reddish brown. The red hue fades away towards the animal's sides and the underside is white. Facial features include white rings around the eyes, as well as a light chin and muzzle. There are black stripes on the forehead, rump and tail. The ears are also tipped with black. the impala has a strong resemblance to the gerenuk in terms of colouration. However, the gerenuk has shorter horns and lacks the black thigh stripes of the impala. The impala has scent glands covered by the black tuft of hair on the back feet. Sebaceous glands are concentrated on the forehead and dispersed on the torso of dominant males. the forehead glands present in males are most active during the mating season, while those of females are only partially developed and do not undergo seasonal changes. The bulbourethral glands are heavier and testosterone levels are nearly double in territorial males in comparison to bachelors. There are four nipples.
Males grow 45–92 cm (18–36 in)-long slender, lyre-shaped horns. The horns have strong ridges and the tips are far apart. They are circular in section and hollow at the base. Their arch-like structure helps the animal to interlock the horns and throw off the opponent. These also protect the cranium from damage.
Like other small to medium-sized African antelopes, the impala has a special dental arrangement on the front lower jaw similar to the toothcomb seen in strepsirrhine primates, which is used during allogrooming to comb the fur and remove ectoparasites. In allogrooming, adult males and females groom one another orally on the head and neck. Each partner generally grooms the other six to twelve times. Allogrooming in females is generally between related individuals, and in males between unrelated individuals.
Of the subspecies, the black-faced is significantly larger as well as darker than the common impala. A recessive gene causes the black coloration in these animals. The black tip on the ear is much larger in the former, and the tail is bushier and almost 30% longer.
Ecology and behavior
The impala are known for their significant leaping ability, reaching heights up to 3 m (9.8 ft.).
Impala are diurnal, most active shortly after dawn and before dusk. They spend the night feeding and resting. They use various kinds of unique visual, olfactory and auditory communication, most notably laying scent-trails and giving loud roars. The roaring process consists of one to three loud snorts with mouth closed, followed by two to ten deep grunts with an open mouth, lifted chin and upraised tail. the most characteristic movement of the impala is its unique leap. When alarmed, the impala run at considerably high speeds and jump to heights of 3 m (9.8 ft.), over bushes and even other impala, covering distances between 8.5 and 9 m (28 and 30 ft.). The impala has an average lifespan of about 15 years in the wild, and nearly 17 years in captivity.
An alert and wary animal, the impala turns motionless on sensing danger. The antelope will scan the vicinity with its eyes to spot the predator, and rotate its ears to hear any sounds. It stares at and moves its head to get a better view of any object it cannot identify. The female, who leads a file of impala on the way to drink, often stops and surveys the surroundings for danger, while the rest in the file stand relaxed. Unlike other antelopes, who run away in the open when disturbed, the impala tries to hide itself in dense vegetation in case of any alarm. Impala are important prey animals for several apex carnivores, including lions, leopards, Cape hunting dogs, spotted hyenas, crocodiles and pythons.
The social behavior of the impala is influenced by the seasons. While the home ranges are heavily fortified in the wet season, they often overlap in the dry season. While the southern impala are much likely to intermix in the dry season, the eastern impala are territorial during this period. Three distinct social groups are formed in the wet season: the territorial males, bachelor herds and female herds. These groups continually break up into smaller herds and reunite. About a third of the adult males hold individual territories, which range from 0.2–0.9 km2 (2,200,000–9,700,000 sq. ft.) in size and may change according to the season. The males demarcate their territories with urine and faeces and defend them against any other male intruders. A study of impala in the Serengeti National Park showed that in 94% of the males, territoriality was observed only for a duration of less than four months. During the mating season males prefer small, easily defended territories, and will sometimes reclaim their old ones from previous mating seasons. These territorial males may or may not have breeding females in their territories. The male will try to control any female herds passing through his territory by herding them towards the center, and will also chase away any bachelor males or juveniles who accompany them.
The bachelor herds comprise non-territorial adult as well as juvenile males, and can have about 30 members. Individuals maintain distances of 2.5–3 m (8.2–9.8 ft.) from one another. Young and old males may interact, but middle-aged males usually avoid one another. The female herds consist of 15-100 individuals, and comprise of breeding herds of females and their young (including young males below four years). The females form clans, and inhabit home ranges 80–180 hectares (200–440 acres; 0.31–0.69 sq.) in size. There is no distinct leader of the female herd, though animals aged five years or more may move independently. Membership in both bachelor and female herds is variable.
Diet
Unlike other antelopes, the impala is an adaptable forager and does not need to migrate long distances. They generally prefer to have water sources nearby, though they can survive on green succulent vegetation if water is scarce. Upper incisors and canines are absent in these ruminants, and the cheek teeth are folded and sharp. It eats both monocot and dicot plants, and also feeds on fruits and Acacia pods whenever available, providing an adequate and nutritious diet under most circumstances. It switches between grazing and browsing depending on the season and habitat. An analysis showed that the diet of impala consists of 45% monocots, 45% dicots and 10% fruits. The proportion of grasses in their diet increases significantly after the first rains (up to 90% of the diet), but declines in the dry season. In the late wet and dry season, forbs are the main item of the diet. Diets are nutritionally poor in the mid-dry season, when impala feed mostly on woody dicots. another study revealed that the dicot proportion in the diet is much higher in bachelors and females than in territorial males.
Impalas most often feed in herds after dawn, before dusk and in the night. They stop feeding if it rains, and face away from the wind. The herd assembles nearer to one another, and begin chewing the cud. The animals who feed on the periphery of the herds are usually more vigilant against predation than those feeding in the center of the herds. A foraging impala will try to defend the patch it is feeding on by lowering its head. A study revealed that time spent in foraging reaches a maximum of 75.5% in the late dry season, decreases through the rainy season, and is minimal in the early dry season (57.8%).
Reproduction
Though males are sexually mature by the time they are a year old, they actually mate only after four years. At this time they establish their own territories. Females can conceive after they are a year and a half old. The annual three-week long breeding season of the impala, also called the rut, begins toward the end of the wet season in May. The males begin preparations for mating in March, including gonadal growth and hormone production, resulting in greater aggressiveness and territoriality in them. Males undergo several physical changes as well, such as darkening of the coat due to greasy secretions from the sebaceous glands, thickening of the neck and acquiring a musky odour. The rut is also influenced by the lunar cycle, with most mating taking place between full moons.
Rutting males fight over dominance, often giving out noisy roars and chasing one another. They walk stiffly and display their neck and horns. Territorial males usually reduce feeding and allogrooming during the mating season, probably in order to devote more time on the outlook for females in estrous. The male detects estrous in the female by testing her urine. The estrous cycle is 12 to 29 days and lasts for 24 to 48 hours. On coming across a breeding female, the excited male begins the courtship by chasing the female about. This gradually turns into a walk, with the female 3–5 m (9.8–16.4 ft.) ahead of her mate. The male flicks his tongue and may nod vigorously. The female allows him to lick her vulva, and holds her tail to the side. The male tries mounting the female, holding his head high and clasping her with his forelegs. Mounting attempts may be repeated every few seconds to every minute or two. The male loses interest in the female after the first copulation, though she is still active and can mate with other males. He is also no longer interested in maintaining an individual territory, and may join the bachelor herds.
The gestational period is of six to seven months; however, the mother has the ability to delay giving birth for an additional month if conditions are harsh. Fawns are born singly. When giving birth (usually in the midday), the female will isolate herself from the herd, despite numerous attempts by the male to keep her in his territory. The female will keep the fawn hidden in an isolated spot for a few days, weeks, or sometimes more, before returning to the herd. There, the fawn will join a nursery group and will go to its mother only to nurse or when predators are near. Fawns are suckled for four to six months. Males which mature are forced out of the group and will join bachelor herds.
Distribution and habitat
The impala is mainly found in southern Africa.
The impala is native to Angola, Botswana, Kenya, Malawi, Mozambique, Namibia, Rwanda, South Africa, Swaziland, Tanzania, Uganda, Zambia and Zimbabwq. Regionally extinct in Burundi, it has been introduced in Gabon. The current distribution of the impala is not much different from its historical range. The black-faced impala is confined to Kaokolan (Namibia) and southwestern Angola. The common impala has been widely introduced in southern Africa.
A typical ecotone species, the impala inhabits savanna grasslands and woodlands close to water sources. They show a preference for acacia savannas for their nutritious grasses and browse in the dry season. while they inhabit Acacia Senegal woodlands in the wet season, they prefer A. drepanolobium savannas in the dry season. Impala in southern Africa have been found to be associated with Colophospermun mopane woodlands. High population densities are observed in places with short grasses. They may also choose habitats with shade, as they are not adapted to dry heat. Black-faced impala, who live in semi-arid environments, also select the interface between wooded savannas and open grassy wetlands. Impala are not known to be part of mountainous ecosystems.
A study found that the reduction of woodland cover and creation of scrublands by the African bush elephants has favoured impala population by increasing the availability of more dry season browse. Earlier, the Baikiaea woodland that has now declined due to elephants provided minimum browse to impala. The newly formed Capparis shrub land, on the other hand, can be a key browsing habitat.
Threats and conservation
Though there are no major threats to the survival of the impala, poaching and natural calamities have significantly contributed to the decline of the black-faced subspecies. The population of the common impala has been estimated to be around 2 million, while that of the black-faced impala is only 2,000-3,000. While the common impala has been listed as of Least Concern by the International Union for Conservation of Nature (IUCN), the black-faced has been rated as Vulnerable. Translocation of the black-faced impala can be highly beneficial in conserving the populations, especially when larger populations are introduced into a place at first.
The common impala is one of the most abundant antelopes in Africa, with about one-quarter of the population occurring in protected areas. The largest populations occur in the Masai Mara and Kajiado (Kenya); the Serengeti, Ruaha National Parks and Selous Game Reserve (Tanzania); Luangwa Valley (Zambia); Okoavago Delta (Botswana); Hwange, Sebungwe and Zambezi Valley (Zimbabwe); and Kruger National Park (South Africa). The rare black-faced impala has been reintroduced from Kaokoland into private farms in Namibia and the Etosha National Park. Population densities vary largely from place to place; from less than 1/km² in Mkomazi National Park (Tanzania) to as high as 135/km² near Lake Kariba (Zimbabwe).
The Giraffe
Etymology
The name "giraffe" has its earliest known origins in the Arabic word zarafa, perhaps from some African language. The name is translated as "fast-walker". There were several Middle English spellings such as jarraf, ziraph, and gerfauntz. The word possibly was derived from the animal's Somali name geri. The Italain form giraffa arose in the 1590s. The modern English form developed around 1600 from the French girafe. The species name Camelopardalis is from Latin.
Kameelperd is also the name for the species in Afrikaans.
Taxonomy and evolution
The giraffe belongs to suborder Ruminantai, and many Ruminantia have been described from the mid-Eocene in Central Asia, Southeast Asia, and North America. The ecological conditions during this period may have facilitated their rapid dispersal. The giraffe is one of only two living species of the family Giraffidae, the other being the okapi. The family was once much more extensive, with over 10 fossil genera described. Their closest known relatives are the extinct climacocerids. They, together with the family Antilocapridae (whose only extant species is the pronghorn), belong to the superfamily Giraffoidea. These animals evolved from the extinct family Palaeomerycidae 8 million years ago (mya) in south-central Europe during the Miocene epoch.
While some ancient giraffids such as Sivatherium had massive bodies, others such as Giraffokeryx, Palaeotragus (possible ancestor of the okapi), samotherium, and Bohlinia were more elongated. Bohlinia entered China and northern India in response to climate change. From here, the genus Giraffa evolved and, around 7 mya, entered Africa. Further climate changes caused the extinction of the Asian giraffes, while the African ones survived and radiated into several new species. G. CamelopardalisG. Camelopardalis arose around 1 mya in eastern Africa during the Pleistocene. Some biologists suggest the modern giraffe descended from G. jumae; others find G. gracillis a more likely candidate. The main driver for the evolution of the giraffes is believed to have been the change from extensive forests to more open habitats, which began 8 mya. Some researchers have hypothesized this new habitat with a different diet, including Acacia, may have exposed giraffe ancestors to toxins that caused higher mutation rates and a higher rate of evolution.
The giraffe was one of the many species first described by Carl Linnaeus in 1758. He gave it the binomial name Cervus Camelopardlis. Morten Trane Brunnich classified the genus Giraffa in 1772. In the early 19th century, Jean-Batiste lamarck believed the giraffe's long neck was an "acquired characteristic", developed as generations of ancestral giraffes strove to reach the leaves of tall trees. This theory was eventually rejected, and scientists now believe the giraffe's neck arose through Darwinian natural selection—that ancestral giraffes with long necks thereby had a competitive advantage that better enabled them to reproduce and pass on their genes.
Subspecies
"Approximate geographic ranges, fur patterns, and phylogenetic relationships between some giraffe subspecies based on mitochondrial DNA sequences. Colored dots on the map represent sampling localities. The phylogenetic tree is a maximun-likelihood phylogram based on samples from 266 giraffes. Asterisks along branches correspond to node values of more than 90% bootstrap support. Stars at branch tips identify paraphyletic haplotypes found in Maasai and Reticulated giraffes".
Up to nine subspecies of giraffe are recognized (with population estimates as of 2010):
- The Nubian giraffe, G. c. camelopardalis, the nominate subspecies, is found in eastern South Sudan and south-western Ethiopia. Fewer than 250 are thought to remain in the wild, although this number is uncertain. It is rare in captivity, although a group is kept at Al Ain Zoo in the United Arab Emirates. In 2003, this group numbered 14.
- The reticulated giraffe, G. c. reticulata, also known as the Somali giraffe, is native to north-eastern Kenya, southern Ethiopia, and Somalia. An estimated no more than 5,000 remain in the wild, and based on International Species Information System records, more than 450 are kept in zoos.
- The Angolan giraffe or the Namibian giraffe, G. c. angolensis, is found in northern Namibia, south-western Zambia, Botswana, and western Zimbabwe. A 2009 genetic study on this subspecies suggests the northern Namib Desert and Etosha National Park populations form a separate subspecies. No more than 20,000 are estimated to remain in the wild; and about 20 are kept in zoos.
- The Kordofan giraffe, G. c. antiquorum, has a distribution which includes southern Chad, the Central African Republic, northern Cameroon, and north-eastern DR Congo. Populations in Cameroon were formerly included in G. c. peralta, but this was incorrect. No more than 3,000 are believed to remain in the wild. Considerable confusion has existed over the status of this subspecies and G. c. peralta in zoos. In 2007, all alleged G. c. peralta in European zoos were shown to be, in fact, G. c. antiquorum. With this correction, about 65 are kept in zoos.
- The Masai giraffe, G. c. tippelskirchi, also known as the Kilimanjaro giraffe, can be found in central and southern Kenya and in Tanzania. No more than 40,000 are thought to remain in the wild, and about 100 are kept in zoos.
- Rothschild's giraffe, G. c. rothschildi named for Walter Rothschild, is also called the Baringo or Ugandan giraffe. Its range includes parts of Uganda and Kenya. Its presence in South Sudan is uncertain. Fewer than 700 are believed to remain in the wild, and more than 450 are kept in zoos.
- The South African giraffe, G. c. giraffa, is found in northern South Africa, southern Botswana, southern Zimbabwe, and south-western Mozambique. Less than 12,000 are estimated to remain in the wild, and around 45 are kept in zoos.
- The Rhodesian giraffe, G. c. thornicrofti, also called the Thornicroft giraffe after Harry Scott Thornicroft, is restricted to the Luangwa Valley in eastern Zambia. No more than 1,500 remain in the wild, with none kept in zoos.
- The West African giraffe, G. c. peralta, also known as the Niger or Nigerian giraffe, is endemic to south-western Niger. Fewer than 220 individuals remain in the wild. Giraffes in Cameroon were formerly believed to belong to this subspecies, but are actually G. c. antiquorum. This error resulted in some confusion over its status in zoos, but in 2007, it was established that all "G. c. peralta" kept in European zoos actually are G. c. antiquorum.
A 2007 study on the genetics of six subspecies—the West African, Rothschild's, reticulated, Masai, Angolan, and South African giraffe—suggests they may, in fact, be separate species. The study deduced from genetic drift in nuclear and mitochondrial DNA (mtDNA) that giraffes from these populations are reproductively isolated and rarely interbreed, though no natural obstacles block their mutual access. This includes adjacent populations of Rothschild's, reticulated, and Masai giraffes. The Masai giraffe may also consist of a few species separated by the Rift Valley. Reticulated and Masai giraffes have the highest mtDNA diversity, which is consistent with the fact that giraffes originated in eastern Africa. Populations further north evolved from the former, while those to the south evolved from the latter. Giraffes appear to select mates of the same coat type, which are imprinted on them as calves. The implications of these findings for the conservation of giraffes were summarised by David Brown, lead author of the study, who told BBC News: "Lumping all giraffes into one species obscures the reality that some kinds of giraffe are on the brink. Some of these populations number only a few hundred individuals and need immediate protection."
The West African giraffe is more closely related to Rothchild's and reticulated giraffes than to the Kordofan giraffe. Its ancestor may have migrated from eastern to northern Africa and then to its current range with the development of the Sahara Desert. At its largest, Lake Chad may have acted as a barrier between West African and Kordofan giraffes during the Holocene.
Appearance and anatomy
Fully grown giraffes stand 5–6 m (16–20 ft) tall, with males taller than females. The average weight is 1,192 kg (2,628 lb) for an adult male and 828 kg (1,825 lb) for an adult female. Despite its long neck and legs, the giraffe's body is relatively short. Located at both sides of the head, the giraffe's large, bulging eyes give it good all-round vision from its great height. Giraffes see in color and their senses of hearing and smell are also sharp. The animal can close its muscular nostrils to protect against sandstorms and ants. The giraffe's prehensile tongue is about 50 cm (20 in) long. It is purplish-black in color, perhaps to protect against sunburn, and is useful for grasping foliage, as well as for grooming and cleaning the animal's nose. The upper lip of the giraffe is also prehensile and useful when foraging. The lips, tongue, and inside of the mouth are covered in papillae to protect against thorns.
The coat has dark blotches or patches (which can be orange, chestnut, brown, or nearly black in color) separated by light hair (usually white or cream in color). Male giraffes become darker as they age. The coat pattern serves as camouflage, allowing it to blend in the light and shade patterns of savanna woodlands. The skin underneath the dark areas may serve as windows for thermoregulation, being sites for complex blood vessel systems and large sweat glands. Each individual giraffe has a unique coat pattern. The skin of a giraffe is mostly gray. It is also thick and allows it to run through thorn bush without being punctured. The fur may serve as a chemical defense, as its parasite repellents give the animal a characteristic scent. At least 11 main aromatic chemicals are in the fur, although indole and 3-methylindole are responsible for most of the smell. Because the males have a stronger odor than the females, the odor may also have sexual function. Along the animal's neck is a mane made of short, erect hairs. The one-meter (3.3-ft) tail ends in a long, dark tuft of hair and is used as a defense against insects.
Skull and ossicones
Both sexes have prominent horn-like structures called ossicones, which are formed from ossified cartilage, covered in skin and fused to the skull at the parietal bones. Being vascularized, the ossicones may have a role in thermoregulation, and are also used in combat between males. Appearance is a reliable guide to the sex or age of a giraffe: the ossicones of females and young are thin and display tufts of hair on top, whereas those of adult males end in knobs and tend to be bald on top. Also, a median lump, which is more prominent in males, emerges at the front of the skull. Males develop calcium deposits that form bumps on their skulls as they age. A giraffe's skull is lightened by multiple sinuses. However, as male’s age, their skulls become heavier and more club-like, helping they become more dominant in combat.The upper jaw has a grooved palate and lacks front teeth. The giraffe's molars have a rough surface.
Legs, locomotion and posture
The front and back legs of a giraffe are about the same length. The radius and ulna of the front legs are articulated by the carpus, which, while structurally equivalent to the human wrist, functions as a knee. The foot of the giraffe reaches a diameter of 30 cm (12 in), and the hoof is 15 cm (5.9 in) high in males and 10 cm (3.9 in) in females. The rear of each hoof is low and the fetlock is close to the ground, allowing the foot to support the animal's weight. Giraffes lack dewclaws and interdigital glands. The giraffe's pelvis, though relatively short, has an ilium that is outspread at the upper ends.
A giraffe has only two gaits: walking and galloping. Walking is done by moving the legs on one side of the body at the same time, then doing the same on the other side. When galloping, the hind legs move around the front legs before the latter move forward, and the tail will curl up. The animal relies on the forward and backward motions of its head and neck to maintain balance and the counter momentum while galloping. The giraffe can reach a sprint speed of up to 60 km/h (37 mph), and can sustain 50 km/h (31 mph) for several kilometers.
A giraffe rests by lying with its body on top of its folded legs, to lie down, the animal kneels on its front legs and then lowers the rest of its body. To get back up, it first gets on its knees and spreads its hind legs to raise its hindquarters. It then straightens its front legs. With each step, the animal swings its head. In captivity, the giraffe sleeps intermittently around 4.6 hours per day, mostly at night. It usually sleeps lying down, however, standing sleeps have been recorded, particularly in older individuals. Intermittent short "deep sleep" phases while lying are characterized by the giraffe bending its neck backwards and resting its head on the hip or thigh, a position believed to indicate paradoxical sleep. If the giraffe wants to bend down to drink, it either spreads its front legs or bends its knees. Giraffes would probably not be competent swimmers as their long legs would be highly cumbersome in the water, although they could possibly float. When swimming, the thorax would be weighed down by the front legs, making it difficult for the animal to move its neck and legs in harmony or keep its head above the surface.
Neck
The giraffe has an extremely elongated neck, which can be up to 2 m (6 ft 7 in) in length, accounting for much of the animal's vertical height. The long neck results from a disproportionate lengthening of the cervical vertebrae, not from the addition of more vertebrae. Each cervical vertebra is over 28 cm (11 in) long. They comprise 52–54 percent of the length of the giraffe's vertebral column, compared with the 27–33 percent typical of similar large ungulates, including the giraffe’s closest living relative, the okapi. This elongation largely takes place after birth, as giraffe mothers would have a difficult time giving birth to young with the same neck proportions as adults. The giraffe's head and neck are held up by large muscles and a nuchal ligament, which are anchored by long dorsal spines on the anterior thoracic vertebrae, giving the animal a hump.
The giraffe's neck vertebrae have ball and socket joints. In particular, the atlas–axis joint (C1 and C2) allows the animal to tilt its head vertically and reach more branches with the tongue. The point of articulation between the cervical and thoracic vertebrae of giraffes is shifted to lie between the first and second thoracic vertebrae (T1 and T2), unlike most other ruminants where the articulation is between the seventh cervical vertebra (C7) and T1.[11] This allows C7 to contribute directly to increased neck length and has given rise to the suggestion that T1 is actually C8, and that giraffes have added an extra cervical vertebra. However, this proposition is not generally accepted, as T1 has other morphological features, such as an articulating rib, deemed diagnostic of thoracic vertebrae, and because exceptions to the mammalian limit of seven cervical vertebrae are generally characterized by increased neurological anomalies and maladies.
There are two main hypotheses regarding the evolutionary origin and maintenance of elongation in giraffe necks. The "competing browsers hypothesis" was originally suggested by Charles Darwin and only challenged recently. It suggests that competitive pressure from smaller browsers, such as kudu, steenbok and impala, encouraged the elongation of the neck, as it enabled giraffes to reach food that competitors could not. This advantage is real, as giraffes can and do feed up to 4.5 m (15 ft) high, while even quite large competitors, such as kudu, can only feed up to about 2 m (6 ft 7 in) high. There is also research suggesting that browsing competition is intense at lower levels, and giraffes feed more efficiently (gaining more leaf biomass with each mouthful) high in the canopy. However, scientists disagree about just how much time giraffes spend feeding at levels beyond the reach of other browsers, and a 2010 study found that adult giraffes with longer necks actually suffered higher mortality rates under drought conditions than their shorter-necked counterparts. This study suggests that maintaining a longer neck requires more nutrients, which puts longer-necked giraffes at risk during a food shortage.
The other main theory, the sexual selection hypothesis, proposes that the long necks evolved as a secondary sexual characteristic, giving males an advantage in "necking" contests (see below) to establish dominance and obtain access to sexually receptive females. In support of this theory, necks are longer and heavier for males than females of the same age, and the former do not employ other forms of combat. However, one objection is that it fails to explain why female giraffes also have long necks.
Internal systems
In mammals, the left recurrent laryngeal nerve is longer than the right; in the giraffe it is over 30 cm (12 in) longer. These nerves are longer in the giraffe than in any other living animal; the left nerve is over 2 m (6 ft 7 in) long. Each nerve cell in this path begins in the brainstem and passes down the neck along the vague nerve, then branches off into the recurrent laryngeal nerve which passes back up the neck to the larynx. Thus, these nerve cells have a length of nearly 5 m (16 ft) in the largest giraffes. The structure of a giraffe's brain resembles that of domestic cattle. The shape of the skeleton gives the giraffe a small lung volume relative to its mass. Its long neck gives it a large amount of dead space, in spite of its narrow windpipe. These factors increase the resistance to airflow. Nevertheless, the animal can still supply enough oxygen to its tissues.
The circulatory system of the giraffe has several adaptations for its great height. Its heart, which can weigh more than 25 lb (11 kg) and measures about 2 ft (61 cm) long, must generate approximately double the blood pressure required for a human to maintain blood flow to the brain. As such, the wall of the heart can be as thick as 7.5 cm (3.0 in). Giraffes have unusually high heart rates for their size, at 150 beats per minute. In the upper neck, a rete Mirabelle prevents excess blood flow to the brain when the giraffe lowers its head. The jugular veins also contain several (most commonly seven) valves to prevent blood flowing back into the head from the inferior vena cava and right atrium while the head is lowered. Conversely, the blood vessels in the lower legs are under great pressure (because of the weight of fluid pressing down on them). To solve this problem, the skin of the lower legs is thick and tight; preventing too much blood from pouring into them.
Giraffes have esophageal muscles that are unusually strong to allow regurgitation of food from the stomach up the neck and into the mouth for rumination. They have four chambered stomachs, as in all ruminants, and the first chamber has adapted to their specialized diet. The giraffe's intestines measure up to 80 m (260 ft) in length and have a relatively small ratio of small to large intestine. The liver of the giraffe is small and compact. A gallbladder is generally present during fetal life, but it may disappear before birth.
Habitat and feeding
Giraffes usually inhabit savannas, grasslands and open woodlands. They prefer Acacia, Commiphora, Combretum and open Terminalia woodlands over denser environments like Brachystegia woodlands.The Angolan giraffe can be found in desert environments. Giraffes browse on the twigs of trees, preferring trees of genera Acacia, Commiphora and Terminalia, which are important sources of calcium and protein to sustain the giraffe's growth rate. They also feed on shrubs, grass and fruit. A giraffe eats around 34 kg (75 lb) of foliage daily. When stressed, giraffes may chew the bark off branches. Although herbivorous, the giraffe has been known to visit carcasses and lick dried meat off bones.
During the wet season, food is abundant and giraffes are more spread out, while during the dry season, they gather around the remaining evergreen trees and bushes. Mothers tend to feed in open areas, presumably to make it easier to detect predators, although this may reduce their feeding efficiency. As a ruminant, the giraffe first chews its food, then swallows it for processing and then visibly passes the half-digested cud up the neck and back into the mouth to chew again. It is common for a giraffe to salivate while feeding. The giraffe requires less food than many other herbivores, because the foliage it eats has more concentrated nutrients and it has a more efficient digestive system. The animal's feces come in the form of small pellets. When it has access to water, a giraffe drinks at intervals no longer than three days.
Giraffes have a great effect on the trees that they feed on, delaying the growth of young trees for some years and giving "waistlines" to trees that are too tall. Feeding is at its highest during the first and last hours of daytime. Between these hours, giraffes mostly stand and ruminate. Rumination is the dominant activity during the night, when it is mostly done lying down.
Social life and breeding habits
While giraffes are usually found in groups, the composition of these groups tends to be open and ever-changing. They have few strong social bonds, and aggregations usually change members every few hours. For research purposes, a "group" has been defined as "a collection of individuals that are less than a kilometer apart and moving in the same general direction." The number of giraffes in a group can range up to 32 individuals. the most stable giraffe groups are those made of mothers and their young, which can last weeks or months. Social cohesion in these groups is maintained by the bonds formed between calves. Mixed-sex groups made of adult females and young males are also known to occur. Sub adult males are particularly social and will engage in play fights. However, as they get older males become more solitary. Giraffes are not territorial, but they have home ranges. Male giraffes occasionally wander far from areas that they normally frequent.
Reproduction is broadly polygamous: a few older males mate with the fertile females. Male giraffes assess female fertility by tasting the female's urine to detect estrus, in a multi-step process known as the freshmen response. Males prefer young adult females over juveniles and older adults. Once an estrous female is detected, the male will attempt to court her. When courting, dominant males will keep subordinate ones at bay. During copulation, the male stands on his hind legs with his head held up and his front legs resting on the female's sides.
Although generally quiet and non-vocal, giraffes have been heard to communicate using various sounds. During courtship, males emit loud coughs. Females call their young by bellowing. Calves will emit snorts, bleats, mooing and mewing sounds. Giraffes also snore, hiss, moan and make flute-like sounds, and they communicate over long distances using infrasound.
Birthing and parental care
Giraffe gestation lasts 400–460 days, after which a single calf is normally born, although twins occur on rare occasions. The mother gives birth standing up. The calf emerges head and front legs first, having broken through the fetal membranes, and falls to the ground, severing the umbilical cord. The mother then grooms the newborn and helps it stand up. A newborn giraffe is about 1.8 m (6 ft) tall. Within a few hours of birth, the calf can run around and is almost indistinguishable from a one-week-old. However, for the first 1–3 weeks, it spends most of its time hiding; its coat pattern providing camouflage. The ossicones, which have lain flat while it was in the womb, become erect within a few days.
Mothers with calves will gather in nursery herds, moving or browsing together. Mothers in such a group may sometimes leave their calves with one female while they forage and drink elsewhere. This is known as a "calving pool". Adult males play almost no role in raising the young, although they appear to have friendly interactions. Calves are at risk of predation, and a mother giraffe will stand over her calf and kick at an approaching predator. Females watching calving pools will only alert their own young if they detect a disturbance, although the others will take notice and follow. The bond a mother shares with her calf varies, though it can last until her next calving. Likewise, calves may suckle for only a month, or as long as a year. Females become sexually mature when they are four years old, while males become mature at four or five years. However, males must wait until they are at least seven years old to gain the opportunity to mate.
Necking
Male giraffes use their necks as weapons in combat, a behavior known as "necking". Necking is used to establish dominance and males that win necking bouts have greater reproductive success. This behavior occurs at low or high intensity. In low intensity necking, the combatants rub and lean against each other. The male that can hold itself more erect wins the bout. In high intensity necking, the combatants will spread their front legs and swing their necks at each other, attempting to land blows with their ossicones. The contestants will try to dodge each other's blows and then get ready to counter. The power of a blow depends on the weight of the skull and the arc of the swing. A necking duel can last more than half an hour, depending on how well matched the combatants are, although most fights do not lead to serious injury, there have been records of broken jaws, broken necks, and even deaths.
After a duel, it is common for two male giraffes to caress and court each other, leading up to mounting and climax. Such interactions between males have been found to be more frequent than heterosexual coupling. In one study, up to 94 percent of observed mounting incidents took place between males. The proportion of same-sex activities varied from 30–75 percent. Only one percent of same-sex mounting incidents occurred between females.
Mortality and health
Giraffes have an unusually long lifespan compared to other ruminants, up to 25 years in the wild. Because of their size, eyesight and powerful kicks, adult giraffes are usually not subject to predation. However, they can fall prey to lions and are regular prey for them in Kruger National Park. Nile crocodiles can also be a threat to giraffes when they bend down to drink. Calves are much more vulnerable than adults, and are additionally preyed on by leopards, spotted hyenas and wild dogs. A quarter to a half of giraffe calves reach adulthood.
Some parasites feed on giraffes. They are often hosts for ticks, especially in the area around the genitals, which has thinner skin than other areas. Tick species that commonly feed on giraffes are those of genera Hyalomma, Amblyomma and Rhipicehalus. Giraffes may rely on red-billed and yellow-billed oxpeckers to clean them of ticks and alert them to danger. Giraffes host numerous species of internal parasite and are susceptible to various diseases. They were victims of the (now eradicated) viral illness rinderpest.
History and cultural significance
Humans have interacted with giraffes for millennia. The San people of southern Africa have medicine dances named after some animals; the giraffe dance is performed to treat head ailments. How the giraffe got its height has been the subject of various African folktales, including one from eastern Africa which explains that the giraffe grew tall from eating too many magic herbs. Giraffes were depicted in art throughout the African continent, including that of the Kiffians, Egyptians and Meroë Nubians. The Kiffians were responsible for a life-size rock engraving of two giraffes that has been called the "world's largest rock art petroglyph". The Egyptians gave the giraffe its own hieroglyph, named 'sir' in Old Egyptian and 'mummy' in later periods. They also kept giraffes as pets and shipped them around the Mediterranean.
The giraffe was also known to the Greeks and Romans, who believed that it was an unnatural hybrid of a camel and a leopard and called it Camelopardalis. The giraffe was among the many animals collected and displayed by the Romans. The first one in Rome was brought in by Julius Caesar in 46 BC and exhibited to the public. With the fall of the Roman Empire, the housing of giraffes in Europe declined. During the middle Ages, giraffes were only known to Europeans through contact with the Arabs, who revered the giraffe for its peculiar appearance.
In 1414, a giraffe was shipped from Malindi to Bengal. It was then taken to China by explorer Zheng He and placed in a Ming Dynasty zoo. The animal was a source of fascination for the Chinese people, who associated it with the mythical Qilin. The Medici giraffe was a giraffe presented to Lorenzo de' Medici in 1486. It caused a great stir on its arrival in Florence. Another famous giraffe was brought from Egypt to Paris in the early 19th century as a gift from Muhammad Ali of Egypt to Charles X of France. A sensation, the giraffe was the subject of numerous memorabilia or "giraffanalia".
Giraffes continue to have a presence in modern culture. Salvador Dalí depicted them with conflagrated manes in some of his surrealist paintings. Dali considered the giraffe to be a symbol of masculinity, and a flaming giraffe was meant to be a "masculine cosmic apocalyptic monster". Several children's books feature the giraffe, including David A. Ufer's The Giraffe Who Was Afraid of Heights, Giles Andreae's Hiraffes Can't Dance and Roald Dahl's The Giraffe and the Pelly and Me. Giraffes have appeared in animated films, as minor characters in Disney's The Lion King and Dumbo, and in more prominent roles in The Wild and in the Madagascar films. Sophie the Giraffe has been a popular teether since 1961. Another famous fictional giraffe is the Toys "R" Us mascot Geoffrey the Giraffe. The giraffe is also the national animal of Tanzania.
The giraffe has also been used for some scientific experiments and discoveries. Scientists have looked at the properties of giraffe skin when developing suits for astronauts and fighter pilots, because the people in these professions are in danger of passing out if blood rushes to their legs. Computer scientists have modeled the coat patterns of several subspecies using reaction–diffusion mechanisms.
The constellation of Camelopardalis, introduced in the seventeenth century, depicts a giraffe. The Tswana people of Botswana saw the constellation Crux as two giraffes – Acrux and Mimosa forming a male, and Gacrux and Delta Crucis forming the female.
Exploitation and conservation status
Giraffes were probably common targets for hunters throughout Africa. Different parts of their bodies were used for different purposes. Their meat was used for food. The tail hairs served as flyswatters, bracelets, necklaces and thread. Shields, sandals and drums were made using the skin, and the strings of musical instruments were from the tendons. The smoke from burning giraffe skins was used by the medicine men of Buganda to treat nose bleeds. The Humr people of Sudan consume the drink Umm Nyolokh; which is created from the liver and marrow of giraffes. Umm Nyolokh often contains DMT and other psychoactive substances from plants the giraffes eat such as Acacia; and is known to cause hallucinations of giraffes, believed to be the giraffes' ghosts by the Humr. In the 19th century, European explorers began to hunt them for sport. Habitat destruction has hurt the giraffe, too: in the Sahel, the need for firewood and grazing room for livestock has led to deforestation. Normally, giraffes can coexist with livestock, since they do not directly compete with them.
The giraffe species as a whole is assessed as Least Concern from a conservation perspective by the IUCN, as it is still numerous. However, giraffes have been extirpated from much of their historic range including Eritrea, Guinea, Mauritania and Senegal. They may also have disappeared from Angola, Mali, and Nigeria, but have been introduced to Rwanda and Swaziland. Two subspecies, the West African giraffe and the Rothschild giraffe, have been classified as Endangered, as wild populations of each of them number in the hundreds. In 1997, Jonathan Kingdon suggested that the Nubian giraffe was the most threatened of all giraffes; as of 2010, it may number fewer than 250, although this estimate is uncertain. Private game reserves have contributed to the preservation of giraffe populations in southern Africa. Giraffe Manor is a popular hotel in Nairobi that also serves as sanctuary for Rothschild's giraffes. The giraffe is a protected species in most of its range. In 1999, it was estimated that over 140,000 giraffes existed in the wild, but estimates in 2010 indicate that fewer than 80,000 remain.
The Warthog
The warthog or common warthog (Phacohoerus africanus) is a wild member of the pig family (Suidae) found in grassland, savanna, and woodland in sub-Saharan Africa. In the past, it was commonly treated as a subspecies of P. aerhiopicus, but today that scientific name is restricted to the desert warthog of northern Kenya, Somalia, and eastern Ethiopia.
The common name comes from the four large, wart-like protrusions found on the head of the warthog, which serve as a fat reserve and are used for defense when males fight. Afrikaans-speaking people call the animal vlakvark, meaning "pig of the plains".
Subspecies
- Nolan warthog (P. a. africanus) (Gmelin, 1788) – Burkina Faso, Ivory Coast, Democratic Republic of the Congo, Ethiopia, Ghana, Guinea-Bissau, Chad, Mauritania, Nigeria, Senegal, Sudan
- Eritrean warthog (P. a. aeliani) Cretzschmar, 1828 – Eritrea, Ethiopia, Djibouti, Somalia
- Central African warthog (P. a. massaicus) Lönnberg, 1908 – Kenya, Tanzania
- Southern warthog (P. a. sundevallii) Lönnberg, 1908 – Botswana, Namibia, South Africa, Zimbabwe
The warthog is medium-sized species; their head-and-body lengths range from 0.9 to 1.5 m (3.0 to 4.9 ft) and shoulder height is from 63.5 to 85 cm (25.0 to 33.5 in). Females, at 45 to 75 kg (99 to 165 lb), are typically a bit smaller and lighter in weight than males, at 60 to 150 kg (130 to 330 lb). A warthog is identifiable by the two pairs of tusks protruding from the mouth and curving upwards. The lower pair, which is far shorter than the upper pair, becomes razor sharp by rubbing against the upper pair every time the mouth is opened and closed. The upper canine teeth can grow to 25.5 cm (10.0 in) long, and are of a squashed circle shape in cross section, almost rectangular, being about 4.5 cm (1.8 in) deep and 2.5 cm (0.98 in) wide. A tusk will curve 90° or more from the root, and will not lie flat on a table, as it curves somewhat backwards as it grows. The tusks are used for digging, for combat with other hogs, and in defense against predators – the lower set can inflict severe wounds.
Warthog ivory is taken from the constantly growing canine teeth. The tusks, more often the upper set, are worked much in the way of elephant tusks with all designs scaled down. Tusks are carved predominantly for the tourist trade in East and Southern Africa.
The head of the warthog is large, with a mane down the spine to the middle of the back. Sparse hair covers the body. Its color is usually black or brown. Tails are long and end with a tuft of hair. Common warthogs do not have subcutaneous fat and the coat is sparse, making them susceptible to extreme environmental temperatures.
Ecology
The warthog is the only pig species that has adapted to grazing and savanna habitats. Its diet is omnivorous, composed of grasses, roots, berries and other fruits, bark, fungi, insects, eggs and carrion The diet is seasonably variable, depending on availability of different food items. During the wet seasons, warthogs graze on short perennial grasses. During the dry seasons, they subsist on bulbs, rhizomes, and nutritious roots. Warthogs are powerful diggers, using both their snouts and feet. Whilst feeding, they often bend their front feet backwards and move around on the wrists. Calloused pads that protect the wrists during such movement form quite early in the development of the fetus. Although they can dig their own burrows, they commonly occupy abandoned burrows of aardvarks or other animals. The warthog commonly reverses into burrows, with its head facing the opening and ready to burst out if necessary. Warthogs will wallow in mud to cope with high temperatures and huddle together to cope with low temperatures.
Although capable of fighting (males aggressively fight each other during mating season) the warthog's primary defense is to flee by means of fast sprinting. The warthog's main predators are humans, lions, leopards, crocodiles, and hyenas. Cheetahs are also capable of catching warthogs of up to their own weight and raptors such as Verreaux's eagle owls and martial eagles sometimes prey on piglets. However, if a female warthog has any piglets, she will defend them very aggressively. On occasion, warthogs have been observed charging and even wounding large predators. Warthogs have also been observed allowing banded mongooses to groom them to remove ticks.
Social behavior and reproduction
Warthogs are not territorial, but instead occupy a home range. Warthogs live in groups called sounders. Females live in sounders with their young and with other females. Females tend to stay in their natal groups, while males leave, but stay within the home range. Sub adult males associate in bachelor groups, but leave alone when they become adults. Adult males only join sounders with estrous females. Warthogs have two facial glands — the tusk gland and the sebaceous gland. Warthogs of both sexes begin to mark around six to seven months old. Males tend to mark more than females. They mark sleeping and feeding areas and waterholes. Warthogs use tusk marking for courtship, for antagonistic behaviors, and to establish status.
Warthogs are seasonal breeders. Rutting begins in the late rainy or early dry season and birthing begins near the start of the following rainy season. The mating system is described as "overlap promiscuity"; the males have ranges overlapping several female ranges, and the daily behavior of the female is unpredictable. Boars employ two mating strategies during the rut. With the "staying tactic", a boar will stay and defend certain females or a resource valuable to them. In the "roaming tactic", boars seek out estrous sows and compete for them. Boars will wait for sows to emerge outside their burrows. A dominant boar will displace any other boar that also tries to court his female. When a sow leaves her den, the boar will try to demonstrate his dominance and then follow her before copulation. For the "staying tactic", monogamy, female-defense polygyny, or resource-defense polygyny is promoted, while the "roaming tactic" promotes scramble-competition polygyny.
The typical gestation period is five to six months. When they are about to give birth, sows temporarily leave their families to farrow in a separate hole. The litter is 2-8 piglets, with 2-4 typical. The sow will stay in the hole for several weeks, nursing her piglets. Warthog sows have been observed to nurse foster piglets if they lose their own litter. This behavior, known as allosucking, makes them cooperative breeders. Allosucking does not seem to be a case of mistaken identity or milk theft, and may be a sign of kin altruism. Piglets begin grazing at about two to three weeks and are weaned by six months. Warthog young quickly attain mobility and stay close to their mothers for defense.
Conservation status
The warthog population in southern Africa is estimated to be about 250,000. Typical densities range between one and 10 per km2 in protected areas, but local densities of 77 per km2 were found on short grass in Nakuru National Park. The species is susceptible to drought and hunting (especially with dogs), which may result in localized extinctions. The common warthog is present in numerous protected areas across its extensive range
The Baboon
Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. The five species are some of the largest nonhominoid members of the primate order; only the mandrill and the drill are larger. Previously, the closely related gelada (genus Theropithecus) and the two species (mandrill and drill) of genus andrillus were grouped in the same genus, and these Old World monkeys are still often referred to as baboons in everyday speech. They range in size and weight depending on species. The Guinea baboon is 50 cm (20 in) and weighs only 14 kg (30 lb) while the largest chacma baboon can be 120 cm (47 in) and weigh 40 kg (90 lb).
Taxonomy and phylogeny
Five species of Papio are commonly recognized, although there is some disagreement about whether they are really full species or subspecies. They are P. ursinus (chacma baboon, found in southern Africa), P. papio (western, red, or Guinea baboon, found in the far western Africa), P. hamadryas (hamadryas baboon, found in the Horn of Africa and southwestern Arabia), P. anubis (olive baboon, found in the north-central African savanna) and P. cynocephalus (yellow baboon, found in south-central and eastern Africa). Many authors distinguish P. hamadryasas a full species, but regard all the others as subspecies of P. cynocephalus and refer to them collectively as "savanna baboons". This may not be helpful: it is based on the argument that the hamadryas baboon is behaviorally and physically distinct from other baboon species, and that this reflects a separate evolutionary history. However, recent morphological and genetic studies of Papio show the hamadryas baboon to be more closely related to the northern baboon species (the Guinea and olive baboons) than to the southern species (the yellow and chacma baboons).
The traditional five-form classification probably under-represents the variation within Papio. Some commentators argue that at least two more forms should be recognized, including the tiny Kinda baboon (P. cynocephalus kindae) from Zambia, DR Congo, and Angola, and the gray-footed baboon (P. ursinus griseipes) found in Zambia, Botswana, Zimbabwe, Mozambique, and northern South Africa. However, current knowledge of the morphological, genetic, and behavioral diversity within Papio is too poor to make any final, comprehensive judgment on this matter.
The five species of baboons in the genus Papio are:
Guinea baboon, Papio papio
Olive baboon, Papio anubis
Yellow baboon, Papio cyncephalus
Chacma baboon, Papio ursinus
Cape chacma, Papio ursinus ursinus
Gray-footed chacma, Papio ursinus griseipes
Ruacana chacma, Papio ursinus raucana
Anatomy and physiology
All baboons have long, dog-like muzzles, heavy, powerful jaws with sharp canine teeth, close-set eyes, thick fur except on their muzzles, short tails, and rough spots on their protruding buttocks, called ischial callosities. These calluses are nerveless, hairless pads of skin that provide for the sitting comfort of the baboon.
All baboon species exhibit pronounced sexual dimorphism, usually in size, but also sometimes in colour or canine development. Males of the hamadryas baboon species also have large white manes.
Behavior and ecology
Baboons are terrestrial (ground dwelling) and are found in open savannah, open woodland and hills across Africa. Their diets are omnivorous, but mostly herbivorous, yet they eat insects and occasionally prey on fish, shellfish, hares, birds, vervet monkeys, and small antelopes. They are foragers and are active at irregular times throughout the day and night. They can raid human dwellings, and in South Africa, they have been known to prey on sheep and goats.
Baboons in captivity have been known to live up to 45 years, while in the wild their life expectancy is about 30 years.
Baboons are able to acquire orthographic processing skills, which form part of the ability to read.
Predators
Their principal predators are humans, the Nile Crocodile, the lion, both the spotted and striped hyena, and the leopard. They are considered a difficult prey for the leopard, though, which is mostly a threat to young baboons. Large males will often confront them by flashing their eyelids, showing their teeth by yawning, making gestures, and chasing after the intruder/predator. Although they obviously aren't a prey species, Baboons have been killed by the black mamba. This usually occurs when a baboon accidentally rouses the snake.
Social systems
Most baboons live in hierarchical troops. Group sizes vary between five and 250 animals (often about 50 or so), depending on specific circumstances, especially species and time of year. The structure within the troop varies considerably between hamadryas baboons and the remaining species, sometimes collectively referred to as savanna baboons. The hamadryas baboons often appear in very large groups composed of many smaller harems (one male with four or so females), to which females from elsewhere in the troop are recruited while they are still too young to breed. Other baboon species have a more promiscuous structure with a strict dominance hierarchy based on the matriline. The hamadryas baboon group will typically include a younger male, but he will not attempt to mate with the females unless the older male is removed.
Baboons can determine from vocal exchanges what the dominance relations are between individuals. When a confrontation occurs between different families or where a lower-ranking baboon takes the offensive, baboons show more interest in this exchange than those between members of the same family or when a higher-ranking baboon takes the offensive. This is because confrontations between different families or rank challenges can have a wider impact on the whole troop than an internal conflict in a family or a baboon reinforcing its dominance.
The collective noun for baboons is commonly "troop".
In the harems of the hamadryas baboons, the males jealously guard their females, to the point of grabbing and biting the females when they wander too far away. Despite this, some males will raid harems for females. Such situations often cause aggressive fights by the males. Visual threats are usually accompanied by these aggressive fights. This would include a quick flashing of the eyelids accompanied by a yawn to show off the teeth. Some males succeed in taking a female from another's harem, called a "takeover". In many species, infant baboons are taken by the males as hostages during fights.
Mating and birth
Baboon mating behavior varies greatly depending on the social structure of the troop. In the mixed groups of savanna baboons, each male can mate with any female. The mating order among the males depends partially on their social ranking, and fights between males are not unusual. There are, however, more subtle possibilities; in mixed groups, males sometimes try to win the friendship of females. To garner this friendship, they may help groom the female, help care for her young, or supply her with food. The probability is high that those young are their offspring. Some females clearly prefer such friendly males as mates. However, males will also take infants during fights to protect themselves from harm.
A female initiates mating by presenting her swollen rump to the male's face.
Females typically give birth after a six-month gestation, usually to a single infant. The young baboon weighs approximately 400 g and has a black epidermis when born. The females tend to be the primary caretaker of the young, although several females will share the duties for all of their offspring.
After about one year, the young animals are weaned. They reach sexual maturity in five to eight years. Baboon males leave their birth group, usually before they reach sexual maturity, whereas females are philopatric and stay in the same group their whole lives.
Relationship with humans
In Egyptian mythology, Babi was the deification of the hamadryas baboon and was therefore a sacred animal. It was known as the attendant of Thoth, so is also called the Sacred Baboon.
Diseases
Herpesvirus papio family of viruses and strains infect baboons. Their effects on humans are unknown.
Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. The five species are some of the largest nonhominoid members of the primate order; only the mandrill and the drill are larger. Previously, the closely related gelada (genus Theropithecus) and the two species (mandrill and drill) of genus andrillus were grouped in the same genus, and these Old World monkeys are still often referred to as baboons in everyday speech. They range in size and weight depending on species. The Guinea baboon is 50 cm (20 in) and weighs only 14 kg (30 lb) while the largest chacma baboon can be 120 cm (47 in) and weigh 40 kg (90 lb).
Taxonomy and phylogeny
Five species of Papio are commonly recognized, although there is some disagreement about whether they are really full species or subspecies. They are P. ursinus (chacma baboon, found in southern Africa), P. papio (western, red, or Guinea baboon, found in the far western Africa), P. hamadryas (hamadryas baboon, found in the Horn of Africa and southwestern Arabia), P. anubis (olive baboon, found in the north-central African savanna) and P. cynocephalus (yellow baboon, found in south-central and eastern Africa). Many authors distinguish P. hamadryasas a full species, but regard all the others as subspecies of P. cynocephalus and refer to them collectively as "savanna baboons". This may not be helpful: it is based on the argument that the hamadryas baboon is behaviorally and physically distinct from other baboon species, and that this reflects a separate evolutionary history. However, recent morphological and genetic studies of Papio show the hamadryas baboon to be more closely related to the northern baboon species (the Guinea and olive baboons) than to the southern species (the yellow and chacma baboons).
The traditional five-form classification probably under-represents the variation within Papio. Some commentators argue that at least two more forms should be recognized, including the tiny Kinda baboon (P. cynocephalus kindae) from Zambia, DR Congo, and Angola, and the gray-footed baboon (P. ursinus griseipes) found in Zambia, Botswana, Zimbabwe, Mozambique, and northern South Africa. However, current knowledge of the morphological, genetic, and behavioral diversity within Papio is too poor to make any final, comprehensive judgment on this matter.
The five species of baboons in the genus Papio are:
- Genus Papio
Guinea baboon, Papio papio
Olive baboon, Papio anubis
Yellow baboon, Papio cyncephalus
- Central yellow baboon, Papio cynocephalus cynocephalus
- Ibean baboon, Papio cynocephalus ibeanus
Chacma baboon, Papio ursinus
Cape chacma, Papio ursinus ursinus
Gray-footed chacma, Papio ursinus griseipes
Ruacana chacma, Papio ursinus raucana
Anatomy and physiology
All baboons have long, dog-like muzzles, heavy, powerful jaws with sharp canine teeth, close-set eyes, thick fur except on their muzzles, short tails, and rough spots on their protruding buttocks, called ischial callosities. These calluses are nerveless, hairless pads of skin that provide for the sitting comfort of the baboon.
All baboon species exhibit pronounced sexual dimorphism, usually in size, but also sometimes in colour or canine development. Males of the hamadryas baboon species also have large white manes.
Behavior and ecology
Baboons are terrestrial (ground dwelling) and are found in open savannah, open woodland and hills across Africa. Their diets are omnivorous, but mostly herbivorous, yet they eat insects and occasionally prey on fish, shellfish, hares, birds, vervet monkeys, and small antelopes. They are foragers and are active at irregular times throughout the day and night. They can raid human dwellings, and in South Africa, they have been known to prey on sheep and goats.
Baboons in captivity have been known to live up to 45 years, while in the wild their life expectancy is about 30 years.
Baboons are able to acquire orthographic processing skills, which form part of the ability to read.
Predators
Their principal predators are humans, the Nile Crocodile, the lion, both the spotted and striped hyena, and the leopard. They are considered a difficult prey for the leopard, though, which is mostly a threat to young baboons. Large males will often confront them by flashing their eyelids, showing their teeth by yawning, making gestures, and chasing after the intruder/predator. Although they obviously aren't a prey species, Baboons have been killed by the black mamba. This usually occurs when a baboon accidentally rouses the snake.
Social systems
Most baboons live in hierarchical troops. Group sizes vary between five and 250 animals (often about 50 or so), depending on specific circumstances, especially species and time of year. The structure within the troop varies considerably between hamadryas baboons and the remaining species, sometimes collectively referred to as savanna baboons. The hamadryas baboons often appear in very large groups composed of many smaller harems (one male with four or so females), to which females from elsewhere in the troop are recruited while they are still too young to breed. Other baboon species have a more promiscuous structure with a strict dominance hierarchy based on the matriline. The hamadryas baboon group will typically include a younger male, but he will not attempt to mate with the females unless the older male is removed.
Baboons can determine from vocal exchanges what the dominance relations are between individuals. When a confrontation occurs between different families or where a lower-ranking baboon takes the offensive, baboons show more interest in this exchange than those between members of the same family or when a higher-ranking baboon takes the offensive. This is because confrontations between different families or rank challenges can have a wider impact on the whole troop than an internal conflict in a family or a baboon reinforcing its dominance.
The collective noun for baboons is commonly "troop".
In the harems of the hamadryas baboons, the males jealously guard their females, to the point of grabbing and biting the females when they wander too far away. Despite this, some males will raid harems for females. Such situations often cause aggressive fights by the males. Visual threats are usually accompanied by these aggressive fights. This would include a quick flashing of the eyelids accompanied by a yawn to show off the teeth. Some males succeed in taking a female from another's harem, called a "takeover". In many species, infant baboons are taken by the males as hostages during fights.
Mating and birth
Baboon mating behavior varies greatly depending on the social structure of the troop. In the mixed groups of savanna baboons, each male can mate with any female. The mating order among the males depends partially on their social ranking, and fights between males are not unusual. There are, however, more subtle possibilities; in mixed groups, males sometimes try to win the friendship of females. To garner this friendship, they may help groom the female, help care for her young, or supply her with food. The probability is high that those young are their offspring. Some females clearly prefer such friendly males as mates. However, males will also take infants during fights to protect themselves from harm.
A female initiates mating by presenting her swollen rump to the male's face.
Females typically give birth after a six-month gestation, usually to a single infant. The young baboon weighs approximately 400 g and has a black epidermis when born. The females tend to be the primary caretaker of the young, although several females will share the duties for all of their offspring.
After about one year, the young animals are weaned. They reach sexual maturity in five to eight years. Baboon males leave their birth group, usually before they reach sexual maturity, whereas females are philopatric and stay in the same group their whole lives.
Relationship with humans
In Egyptian mythology, Babi was the deification of the hamadryas baboon and was therefore a sacred animal. It was known as the attendant of Thoth, so is also called the Sacred Baboon.
Diseases
Herpesvirus papio family of viruses and strains infect baboons. Their effects on humans are unknown.
The Black-Faced Impala
Taxonomy
Scientific Name: Aepyceros melampus
Species Authority: (Lichtenstein, 1812)
Common Name/s: English – Black-faced Impala
Taxonomic Notes: Two subspecies are generally recognized, supported by molecular data (Nersting and Arctander 2001; Lorenzen et al. 2006): the Common Impala (A.m. melampus) and the Black-faced Impala (A.m. petersi).
Justification:
Listed as Least Concern as although Impala have been eliminated from some parts of their range (such as Burundi), they are still relatively widespread, common and abundant in numerous protected areas across their range. The population is estimated at almost 2 million, of which about 50% are on private land (stable or increasing) and 25% in protected areas (stable). The remaining 25% are stable or decreasing. Its future is secure as long as it continues to occur in large, adequately protected and managed populations in protected areas and private farms and conservancies. Most of the species' largest populations are stable or increasing.
Geographic Range
The Black Faced Impala formerly occurred widely in southern and East Africa, from central and southern Kenya and north-east Uganda to northern KwaZulu-Natal, west to Namibia and southern Angola. Their current distribution range remains largely unchanged from their historical range, although it has been eliminated from parts by hunting for meat and the spread of settlement (for example, they now only occur in south-west Uganda, and have been extirpated from Burundi) (East 1999; Fritz and Bourgarel in press).
Range Description:
In Namibia, the Black-faced Impala is naturally confined to the Kaokoland in the north-west, and neighbouring south-western Angola. Kaokoland was set aside as a protected area in 1928, when it formed part of Etosha N.P., but lost its protection status in 1970. To guard against its extinction, Black-faced Impala were translocated to south-western Etosha on the edge of the historic Black-faced Impala range (Green and Rothstein 1998). Today, this subspecies occurs between the Otjimborombonga area (ca 12°45'E) and Swartbooisdrift on the Cunene R., southward to the Kaoko Otavi area in the south-western part of the Etosha N.P., and the Kamanjab District just south of the Park (Fritz and Bourgarel in press). There is no information on the current status of this subspecies in Angola (Crawford-Cabral and Veríssimo 2005)
Common Impala have been introduced to numerous privately owned game ranches and small reserves throughout southern Africa. Impala have also been introduced in two protected areas in Gabon (P. Chardonnet pers. comm.).
Native Countries:
Angola;Botswana;Kenya;Malawi;Mozambique;Namibia;Rwanda;SouthAfrica;Swaziland;Tanzania,UnitedRepublicof;Uganda;Zambia; Zimbabwe
Regionally extinct:
Burundi
Introduced:
Gabon
Population
Population estimates are available for most of the Impala’s current range. East (1999) summed these estimates to produce a total population of 1,584,000 Common Impala and 2,200 Black-faced Impala, but the former does not allow for undercounting in aerial surveys or those areas for which population estimates are unavailable. Correcting for undercounting biases, East (1999) estimated the total numbers of Common Impala at ~2 million.
East's estimate of 2,200 for Black-faced Impala is slightly lower than that estimated by Green and Rothstein (1998), who estimated numbers in Etosha at around 1,500 individuals, with an additional 1,200 on private land, and the total population in Kaokoland at around 500. As of 2007, numbers in Etosha and private ranches are estimated at about 3,200 with a further 50-100 on conservancies (all stable and increasing); numbers in the north-west (the original native range) may number approximately 1,000 (J. Jackson in litt to ASG 2007).
As noted by Fritz and Bourgarel (in press), actual recorded densities of Impala vary substantially, from less than 1/km² in Mkomazi National Park (Tanzania) to as many as 135/km² on the shores of Lake Kariba in Zimbabwe (Bourgarel 1998). In the wooded savanna of Akagera N.P. in Rwanda, where Monfort (1972) recorded densities of 214/km², total numbers declined by about 75-80% between 1990 and 1998 (Williams and Ntayombya 1999).
Habitat and Ecology
The Impala is a water-dependent and typical ecotone species, associated with light woodlands and savannas, selecting open Acacia savannas with nutrient-rich soils providing good-quality grass, and high-quality browse in the dry season (Fritz and Bourgarel in press). In their semi-arid environment, Black-faced Impala also select the interface between wooded savanna and open grassy vleis (Joubert 1971; Matson et al. 2005).
Threats
Major Threat(s):
There are currently no major threats to the species. Poaching, livestock development and severe drought were the main factors contributing to the decline of Black-faced Impala. The reintroduction of 180 individuals from Kaokoland to the west of Etosha National Park between 1968 and 1971 helped promote the conservation of the subspecies, and a few were translocated from Etosha to private game farms in Namibia (Fritz and Bourgarel in press).
However, the introduction of Common Impala to ranches and conservancies neighbouring Etosha National Park may represent a threat to the Black-faced subspecies through hybridization. Green and Rothstein (1998) earlier estimated that about one-quarter of all privately owned Black-faced Impala occur in mixed herds with Common Impala. In a recent study, Lorenzen and Siegismund (2004) analysed 127 Black-faced Impala individuals from five subpopulations in Etosha National Park to determine whether any hybridization had taken place within the park, but could not find any evidence for hybridization between the two subspecies having taken place.
Conservation Actions:
The Common Impala is one of the most abundant antelopes in Africa, with about one-quarter of the population occurring in protected areas. The largest numbers occurring in areas such as the Mara and Kajiado (Kenya), Serengeti, Ruaha and Selous (Tanzania), Luangwa Valley (Zambia), Okavango (Botswana), Hwange, Sebungwe and the Zambezi Valley (Zimbabwe), Kruger (South Africa) and on private farms and conservancies (South Africa, Zimbabwe, Botswana and Namibia) (East 1999). Its future is secure as long as it continues to occur in large, adequately protected and managed populations in protected areas and private farms and conservancies.
The main surviving populations of the Black-faced Impala occur in Etosha National Park and private farms in Namibia. The numbers of the Black-faced Impala should continue to increase in protected areas and on private land, although it remains at risk from hybridization with the Common Impala (East 1999). The Namibian government has a management plan to eliminate hybridization with Common Impala and strictly regulate harvests. The Namibian Professional Hunters Association has a Black-faced Impala committee and the NGO Conservation Force has a long-term involvement in all aspects of its conservation including funding of the management plan. Good management practices make the future of the taxon secure for now (John J. Jackson III, in litt. to ASG, August 2007).
The Damara Dik-Dik
A dik-dik is a small antelope in the genus Madoqua that lives in the bushlands of eastern and southern Africa. Dik-diks stand about 30–40 cm (12–16 in) at the shoulder, are 50–70 cm (20–28 in) long, weigh 3–6 kg (7–16 lb) and can live for up to 10 years. Dik-diks are named for the alarm calls of the females. In addition to the females' alarm call, both the male and female make a shrill, whistling sound. These calls may alert other animals to predators.
Physical characteristics
Female dik-diks are somewhat larger than males. The males have horns, which are small (about 3 in or 7.5 cm), slanted backwards and longitudinally grooved. The hair on the crown forms an upright tuft that sometimes partially conceals the short, ribbed horns of the male. The upper body is gray-brown, while the lower parts of the body, including the legs, belly, crest, and flanks, are tan. A bare black spot below the inside corner of each eye contains a preorbital gland that produces a dark, sticky secretion. Dik-diks insert grass stems and twigs into the gland to scent-mark their territories.
To prevent overheating, dik-diks have elongated snouts with bellows-like muscles through which blood is pumped. Airflow and subsequent evaporation cools this blood before it is recirculated to the body. However, this panting is only implemented in extreme conditions—dik-diks can tolerate air temperatures of up to 40 °C (104 °F).
Habitat
The dik-dik lives in shrublands and savannas of eastern Africa. Dik-diks seek habitats with plentiful supply of edible plants such as shrubs. Dik-diks may live in places as varied as dense forest or open plain, but they require good cover and not too much tall grass. They usually live in pairs in territories of about 5 hectares (12 acres). The territories are often in low, shrubby bushes (sometimes along dry, rocky streambeds) with plenty of cover. Dik-diks can blend in with their surroundings, because of their dusty colored fur. Dik-diks have a series of runways through and around the borders of their territories.
Diet
Dik-diks are herbivores. Their diet mainly consists of foliage, shoots, fruit and berries, but little or no grass. They receive sufficient amounts of water from their food, making drinking unnecessary. Like all even-toed ungulates, they digest their food with the aid of micro-organisms in their four-chambered stomachs. After initial digestion, the food is repeatedly eructated and rechewed, a process known also as rumination, or 'chewing the cud'. Dik-diks' tapering heads may help them eat the leaves between the spines on the acacia trees, and feed while still keeping their head high to detect predators.
Reproduction
Dik-diks are monogamous, and conflicts between territorial neighbors are rare. When they occur, the males from each territory dash at each other, stop short, vigorously nod their heads and turn around. They will repeat this process, increasing the distance each time until one stops. Males mark their territories with dung piles, and cover the females' dung with their own. Monogamy in dik-diks may be an evolutionary response to predation; surrounded by predators, it is dangerous to explore, looking for new partners. Pairs spend about 64% of their time together. Males, but not females, will attempt to obtain extra-pair mating when the opportunity arises.
Females are sexually mature at 6 months and males at 12 months. The female gestates for 169 to 174 days and bears a single offspring. This happens up to twice a year (at the start and finish of the rainy season). Unlike other ruminants, the dik-dik is born with its forelegs laid back alongside its body, instead of them being stretched forward. Females weigh about 560 to 680 g (1.2–1.4 lb) at birth, while males weigh 725 to 795 g (1.5–1.7 lb). The mother lactates for six weeks, feeding her fawn for no longer than a few minutes at a time. The survival rate for young dik-diks is 50%. The young stay concealed for a time after birth, but grow quickly and reach full size by seven months. At that age, the young are forced to leave their parents' territory. The fathers run the sons off the territory and the mothers run off the daughters.
Predators
Dik-diks are hunted primarily by monitor lizards, caracals, lions, hyenas, wild dogs and humans. Other predators include leopards, cheetahs, jackals, baboons, eagles, hawks and pythons. Dik-diks' adaptation to predation include excellent eyesight and the ability to reach speeds up to 42 km (26 mi) an hour.
Classification
The four species of dik-dik are:
- Madoqua gunther (Günther, 1894) – Günther's dik-dik
- M. kirkii (Günther, 1880) – Kirk's dik-dik
- M. piacentinii (Drake-Brockman, 1911) – Silver dik-dik
- M. saltiana (Desmarest, 1816) – Salt's dik-dik
The Black-Backed Jackal
The black-backed jackal (Canis mesomelas), also known as the silver-backed or red jackal, is a species of jackal which inhabits two areas of the African continent separated by roughly 900 km. One region includes the southernmost tip of the continent, including South Africa, Namibia, Botswana, and Zimbabwe. The other area is along the eastern coastline, including Kenya, Somalia, Djibouti and Ethiopia. It is listed by the IUCN as least concern, due to its widespread range and adaptability, although it is still persecuted as a livestock predator and rabies vector. The fossil record indicates the species is the oldest extant member of the genus Canis. Although the most lightly built of jackals, it is the most aggressive, having been observed to singly kill animals many times its own size, and its intrapack relationships are more quarrelsome.
Evolution
The black-backed jackal is an exceptionally stable and ancient form of canid, with many fossils dating as far back as the Pleistocene epoch. Fossil jackals discovered in the Transvaal cave are roughly the same size as their descendents, though their nasal bones differ in size. Although numerous fossils dating back to two million years ago have been found in Kenya, Tanzania, and South Africa, they are entirely absent in Ethiopia, indicating the species has never expanded past sub-Saharan Africa. Mitochondrial DNA analyses display a large sequence divergence in black-backed jackals from other jackal species, indicating they diverged 2.3–4.5 million years ago.
Physical description
Black-backed jackals are small, fox-like canids and are the smallest of the three species called jackal. They measure 30–48 cm (12–19 in) in shoulder height and 60–90 cm (24–35 in) in length. The tail measures 26–40 cm (10–16 in) in length. Weight varies according to location; East African jackals weigh 7-13.8 kg (15-30 lb). Male jackals in Zimbabwe weigh 6.8-9.5 kg (15-21 lb), while females weigh 5.4–10 kg (12-22 lb). Their skulls are elongated, with pear-shaped braincases and narrow rostra. The black-backed jackal's skull is similar to that of the side-striped jackal, but is less flat, and has a shorter, broader rostrum. Its sagittal crest and zygomatic arches are also heavier in build. Its carnassials are also larger than those of its more omnivorous cousin. Black-backed jackals are taller and longer than golden jackals, but have smaller heads.
The general colour is reddish-brown to tan, while the flanks and legs are redder. Males tend to be more brightly coloured than females, particularly in their winter coat. The back is intermixed with silver and black hairs, while the underparts are white. Their tails have a black tip, unlike side-striped jackals, which have white-tipped tails. The back of the ears are light yellowish-brown, well covered with hair without and within. The hair of the face measures 10–15 mm in length, and lengthens to 30–40 mm on the rump. The guard hairs of the back are 60 mm on the shoulder, decreasing to 40 mm at the base of the tail. The hairs of the tail are the longest, measuring 70 mm in length.
Behavior
Social behavior and reproduction
Jackals usually den in holes made by other species, though they will occasionally dig their own; females will dig tunnels 1–2 metres in depth with a 1-metre-wide entrance. Black-backed jackals are monogamous and territorial animals, whose social organisation greatly resembles that of golden jackals. However, unlike the latter species, the assistance of elder offspring in helping raise the pups of their parents has a greater bearing on pup survival rates. During the mating season, they become increasingly more vocal and territorial, with dominant animals preventing same-sex subordinates from mating through constant harassment. In southern Africa, mating occurs from late May to August, with a 60-day gestation period. Pups are born from July to October. Summer births are thought to be timed to coincide with population peaks of vlei rats and four-striped grass mice, while winter births are timed for ungulate calving seasons. Litters usually consist of three to six pups. For the first three weeks of their lives, the pups are kept under constant surveillance by their mother, while the father and elder offspring provide food. They typically leave the den after three weeks, and become independent at six to eight months. Pups have drab coloured coats, which only reach full intensity at the age of two years. Unlike golden jackals, which have comparatively amicable intrapack relationships, black-backed jackal pups become increasingly quarrelsome as they age, and establish more rigid dominance hierarchies. Dominant cubs will appropriate food, and become independent at an earlier age.
Diet
Black-backed jackals are omnivores, which feed on invertebrates, such as beetles, grasshoppers, crickets, termites, millipedes, spiders and scorpions. They will also feed on mammals, such as rodents, hares and young antelopes up to the size of topi calves. They will also feed on carrion, lizards, and snakes. A pair of black-backed jackals in the Kalahari desert was observed to kill and devour a kori bustard and, on a separate occasion, a black mamba via prolonged harassment of the snake and crushing of the snake's head. Black-backed jackals will occasionally feed on fruits and berries. In coastal areas, they will feed on beached marine mammals, seals, fish and mussels. A single jackal is capable of killing a healthy adult impala (individual infirm). Adult dik dik and Thomson's gazelles seem to be the upper limit of their killing capacity, though they will target larger species if they are sick, with one pair having been observed to harass a crippled bull rhinoceros. They typically kill tall prey by biting at the legs and loins, and will frequently go for the throat. In Serengeti woodlands, they feed heavily on African Grass Rats. In East Africa, during the dry season, they hunt the young of gazelles, impalas, topi, tsessebe and warthogs. In South Africa, black-backed jackals frequently prey on antelopes (primarily impala and springbok and occasionally duiker, reedbuck and steenbok), carrion, hares, hoofed livestock, insects, and rodents. They will also prey on small carnivores, such as mongooses, polecats and wild cats. On the coastline of the Namib Desert, jackals feed primarily feed on marine birds (mainly Cape and white-breasted cormorants and jackass penguins), mammals (including Cape fur seals), fish, and insects.
In the Ngorongoro Crater, where both black-backed and golden jackals are found in equal numbers, the former species congregates at carcasses in large numbers far more readily, and is bolder in approaching larger predators.
Interspecific predatory relationships
Eagles are the primary threat to pups; bateleur eagles will carry off pups up to the age of 10 weeks, while the larger martial eagles will even target adults. Golden jackals will also kill unprotected pups.
The main threat to adults are leopards, although they may also be killed by lions, cheetahs and spotted hyenas.
Although smaller than side-striped jackals, the more aggressive black-backed jackals have been observed to dominate them in direct encounters.
Vocalisations
Sounds made by black-backed jackals include yelling, yelping, woofing, whining, growling and cackling. When calling to one another, they emit an abrupt yelp followed by a succession of shorter yelps. Jackals of the same family will answer each other's calls, while ignoring those of strangers. When threatened by predators, they yell loudly. Black-backed jackals in southern Africa are known to howl much like golden jackals. They woof when startled, and cackle like foxes when trapped.
Habitat
In their northeastern range, black-backed jackals inhabit habitat zones intermediate to the grasslands favoured by golden jackals and the woodlands favoured by side-striped jackals. In the Serengeti, they predominate in Acacia and Commiphora woodlands, while the golden species limits itself to open plains. In their southern range, where golden jackals are absent, black-backed jackals are found in more open and arid habitats, though preferring areas with scattered brush.
Diseases and parasites
Black-backed jackals can carry diseases such as rabies, canine parvovirus, canine distemper, canine adenovirus, Ehrlichia canis and African horse sickness. Jackals in Etosha National Park may carry anthrax. Black-backed jackals are major rabies vectors, and have been associated with epidemics, which appear to cycle every four to eight years. Jackals in Zimbabwe are able to maintain rabies independently of other species. Although oral vaccinations are effective in jackals, the long-term control of rabies continues to be a problem in areas where stray dogs are not given the same immunisation.
Jackals may also carry trematodes such as Athesmia, cestodes such as Dipylidium caninum, Echinococcus granulosus, Joyeuxialla echinorhyncoides, J. pasqualei, Mesocestoides lineatus, Taenia erythraea, T. hydatigena, T. jackhalsi, T. multiceps, T. pungutchui, and T. serialis. Nematodes carried by black-backed jackals include Ancylostoma braziliense, A. caninum, A. martinaglia, A. somaliense, A. tubaeforme, and Physaloptera praeputialis, and protozoans such as Babesia canis, Ehrlichia canis, Hepatozoon canis, Rickettsia canis, Sarcocytis spp., Toxoplasma gondii, and Trypanosoma congolense. Mites may cause sarcoptic mange. Tick species include Amblyomma hebraeum, A. marmoreum, A. nymphs, A. variegatum, Boophilus decoloratus, Haemaphysalis leachii, H. silacea, H. spinulosa, Hyelomma spp., Ixodes pilosus, I. rubicundus, Rhipicephalus appendiculatus, R. evertsi, R. sanguineus, and R. simus. Flea species include Ctenocephalides cornatus, Echidnophaga gallinacea, and Synosternus caffer.
Relationships with humans
In folklore
Black-backed jackals feature prominently in the folklore of the Khoikhoi, where it is often paired with the lion, whom it frequently outsmarts or betrays with its superior intelligence. One story explains that the black-backed jackal gained its dark saddle when it offered to carry the sun on its back.
Livestock predation
Black-backed jackals will occasionally hunt domestic animals, including dogs, cats, pigs, goats, sheep, and poultry, with sheep tending to predominate. They rarely target cattle, though cows giving birth may be attacked. Jackals can be a serious problem for sheep farmers, particularly during the lambing season. Sheep losses to black-backed jackals in a 440 km study area in KwaZulu-Natal consisted of 0.05% of the sheep population. Of 395 sheep killed in a sheepfarming area in KwaZulu-Natal, 13% were killed by jackals. Jackals usually kill sheep via a throat bite, and will begin feeding by opening the flank and consuming the flesh and skin of the flank, heart, liver, some ribs, haunch of hind leg, and sometimes the stomach and its contents. In older lambs, the main portions eaten are usually heart and liver. Usually only one lamb per night is killed in any one place, but sometimes two and occasionally three may be killed. In sheep farming areas, black-backed jackals will time their pup births to coincide with the lambing season. The oral history of the Khoikhoi indicates they have been a nuisance to pastoralists long before European settlement. South Africa has been using fencing systems to protect sheep from jackals since the 1890s, though such measures have mixed success, as the best fencing is expensive, and jackals can easily infiltrate cheap wire fences.
Hunting
Due to livestock losses to jackals, many hunting clubs were opened in South Africa in the 1850s. Black-backed jackals have never been successfully eradicated in hunting areas, despite strenuous attempts to do so with dogs, poison and gas. Black-backed jackal coursing was first introduced to the Cape Colony in the 1820s by Lord Charles Somerset who, as well as an avid fox hunter, sought a more effective method of managing jackal populations, as shooting proved ineffective. Coursing jackals also became a popular pastime in the Boer Republics, particularly in Orange Free State, where it was standard practise to flush them from their dens with terriers and send greyhounds in pursuit. This was fraught with difficulty, however, as jackals were difficult to force out of their earths (dens), and usually had numerous exits from which to escape. This method is still used by farmers in Free State. In the western Cape in the early 1900s, dogs bred by crossing foxhounds, lurchers and borzoi were used.
Spring traps with metal jaws were also effective, though poisoning by strychnine became more common by the late 19th century. Strychnine poisoning was initially problematic, as the solution had a bitter taste, and could only work if swallowed. Consequently, many jackals learned to regurgitate poisoned baits, thus inciting wildlife managers to use the less detectable crystal strychnine rather than liquid. The poison was usually placed within sheep carcasses or in balls of fat, with great care being taken to avoid leaving any human scent on them. Black-backed jackals were not a popular quarry in the 19th century, and are rarely mentioned in hunter's literature. By the turn of the century, jackals became increasingly popular quarry as they encroached upon human habitations after sheep farming and veld burning diminished their natural food sources. Although poisoning had been effective in the late 19th century, its success rate in eliminating jackals waned in the 20th century, as jackals seemed to be learning to distinguish poisoned foods. Today, professional South African hunters commonly lure jackals by using recorded jackal calls.
The Tswana people often made hats and cloaks out of black-backed jackal skins. Between 1914 and 1917, 282,134 jackal pelts (nearly 50,000 a year) were produced in South Africa. Demand for pelts grew during the First World War, and were primarily sold in Cape Town and Port Elizabeth. Jackals in their winter fur were in great demand, though animals killed by poison were less valued, as their fur would shed.
In popular culture
- In the American horror films The Omen (1976), Damien: Omen II (1978), and Omen III: The Final Conflict (1981), Antichrist Damien Thorn is portrayed as having the genetic makeup of a jackal rather than that of a typical human being.
The Klipspringer
The klipspringer (Oreotragus oreotragus), is a small species of African antelope.
Name
The word klipspringer literally means "rock jumper" in Afrikaans. The klipspringer is also known colloquially as a mvundla (from the Xhosa umvundla, meaning "rabbit").
Distribution and habitat
The klipspringer lives from the Cape of Good Hope, where it is found in mountain fynbos, through the rest of Southern Africa, where it is found in rocky koppies in woodland and savanna, north to East Africa and into the highly mountainous highlands of Ethiopia.
Description
Reaching approximately 58 cm (22 inches) at the shoulder, klipspringers are smaller than most other antelopes. They stand on the tips of their hooves and can fit all four hooves on a piece of cliff the size of a Canadian dollar coin, roughly 30 mm in diameter. Male klipspringer horns are usually about 10–15 cm (4–6 inches) long. Female klipspringers in eastern African populations also have horns.
With a thick and dense, speckled "salt and pepper" patterned coat of an almost olive shade, klipspringers blend in well with the koppies (rock outcrops) on which they can usually be found. However, their agility on rocks and crags is so extreme that their most dangerous enemies are eagles and humans, so camouflage is not as important to them as to most other antelope.
Predators
Klipspringers are preyed upon by leopards, caracals, eagles and humans.
Diet
Klipspringers are herbivores, eating plants growing in mountainous habitats and rocky terrain. They never need to drink, since the succulents they consume provide them with enough water to survive.
Behaviour
Klipspringers form breeding pairs rather than herds. The pairs mate for life and will spend most of their lives in close proximity to each other. When one klipspringer is eating, the other will assume lookout duty, helping to keep the pair aware of any predators.
The mating season for klipspringers is from September through January. The gestation period is about 214 days.
The Lechwe
The lechwe, or southern lechwe, (Kobus leche) is an antelope found in Botswana, Zambia, southeastern Democratic Republic of the Congo, northeastern Namibia, and eastern Angola, especially in the Okavango Delta, Kafue Flats and Bangweulu Swamps.
Lechwe stand 90 to 100 cm (35 to 39 in) at the shoulder and weigh from 70 to 120 kg (150 to 260 lb). They are golden brown with white bellies. Males are darker in colour, but general hue varies depending on subspecies. The long, spiral-structured horns are vaguely lyre-shaped, they are found only in males. The hindlegs are somewhat longer in proportion than in other antelopes, to ease long-distance running in marshy soil.
Lechwe are found in marshy areas where they eat aquatic plants. They use the knee-deep water as protection from predators. Their legs are covered in a water-repellant substance which allows them to run quite fast in knee-deep water.
Lechwe are diurnal. They gather in herds which can include many thousands of individuals. Herds are usually all of one sex, but during mating season they mix.
Subspecies
Traditionally, four subspecies of the lechwe have been recognized. Additionally, the Upemba lechwe, which only was described in 2005, is treated as a subspecies of the lechwe by some authorities.
- Red lechwe or Zambesi lechwe (K. l. leche) - most of range, overall tawny-fawn with black to front of front legs
- Kafue lechwe or brown lechwe (K. l. kafuensis) - Kafue Flats, as previous, but front legs almost entirely black, vulnerable.
- Roberts' lechwe or Kawambwa lechwe (K. l. robertsi) - formerly near Kawambwa, extinct.
- Black lechwe or Bangweulu lechwe (K. l. smithemani) - Bangweulu Swamps, adult males blackish, vulnerable
- Cape lechwe or Venter's lechwe (K. l. venterae) - now extinct, but formerly inhabited the marshes and fens of the North West, Free State, Northern Cape and Eastern Cape Provinces of South Africa, as far south as Cradock and Tarkastad
The Ostrich
The Ostrich or Common Ostrich (Struthio camelus) is either one or two species of large flightless birds native to Africa, the only living member(s) of the genus Struthio, which is in the ratite family. Some analyses indicate that the Somali Ostrich may be better considered a full species separate from the Common Ostrich, but most taxonomists consider it to be a subspecies.
The ostrich shares the order Struthioniformes with the kiwis, emus, rheas, and cassowaries. It is distinctive in its appearance, with a long neck and legs, and can run at up to about 70 km/h (43 mph), the fastest land speed of any bird.[4] The ostrich is the largest living species of bird and lays the largest eggs of any living bird (extinct elephant birds of Madagascar and the giant moa of New Zealand laid larger eggs).
The ostrich's diet consists mainly of plant matter, though it also eats invertebrates. It lives in nomadic groups of 5 to 50 birds. When threatened, the ostrich will either hide itself by lying flat against the ground, or run away. If cornered, it can attack with a kick of its powerful legs. Mating patterns differ by geographical region, but territorial males fight for a harem of two to seven females.
The ostrich is farmed around the world, particularly for its feathers, which are decorative and are also used as feather dusters. Its skin is used for leather products and its meat is marketed commercially.
Description
Ostriches usually weigh from 63 to 145 kilograms (139–320 lb), Ostriches of the East African race (S. c. massaicus) averaged 115 kg (254 lb) in males and 100 kg (220 lb) in females, while the nominate subspecies was found to average 111 kg (245 lb) in unsexed adults. Exceptional male ostriches (in the nominate subspecies) can weigh up to 156.8 kg (346 lb). At sexual maturity (two to four years), male ostriches can be from 2.1 to 2.8 m (6 ft 11 in to 9 ft 2 in) in height, while female ostriches range from 1.7 to 2 m (5 ft 7 in to 6 ft 7 in) tall. New chicks are fawn in colour, with dark brown spots. During the first year of life, chicks grow at about 25 cm (9.8 in) per month. At one year of age, ostriches weigh approximately 45 kilograms (99 lb). Their lifespan is up to 40–45 years.
The feathers of adult males are mostly black, with white primaries and a white tail. However, the tail of one subspecies is buff. Females and young males are greyish-brown and white. The head and neck of both male and female ostriches is nearly bare, with a thin layer of down. The skin of the female's neck and thighs is pinkish gray, while the male's is blue-gray, gray or pink dependent on subspecies.
The long neck and legs keep their head up to 2.8 m (9 ft) above the ground, and their eyes are said to be the largest of any land vertebrate: 50 mm (2.0 in) in diameter; they can therefore perceive predators at a great distance. The eyes are shaded from sunlight from above. However, the head and bill are relatively small for the birds' huge size, with the bill measuring 12 to 14.3 cm (4.7 to 5.6 in).
Their skin varies in colour depending on the subspecies, with some having light or dark gray skin and others having pinkish or even reddish skin. The strong legs of the ostrich are unfeathered and show bare skin, with the tarsus (the lowest upright part of the leg) being covered in scales: red in the male, black in the female. The tarsus of the ostrich is the largest of any living bird, measuring 39 to 53 cm (15 to 21 in) in length. The bird has just two toes on each foot (most birds have four), with the nail on the larger, inner toe resembling a hoof. The outer toe has no nail. The reduced number of toes is an adaptation that appears to aid in running, useful for getting away from predators. Ostriches can run at a speed over 70 km/h (43 mph) and can cover 3 to 5 m (9.8 to 16.4 ft) in a single stride. The wings reach a span of about 2 metres (6 ft 7 in), and the wing chord measurement of 90 cm (35 in) is around the same size as for the largest flying birds. The wings are used in mating displays and to shade chicks. The feathers lack the tiny hooks that lock together the smooth external feathers of flying birds, and so are soft and fluffy and serve as insulation. Ostriches can tolerate a wide range of temperatures. In much of their habitat, temperatures vary as much as 40 °C (100 °F) between night and day. Their temperature control mechanism relies on action by the bird, which uses its wings to cover the naked skin of the upper legs and flanks to conserve heat, or leaves these areas bare to release heat. They have 50–60 tail feathers, and their wings have 16 primary, four alular and 20–23 secondary feathers.
The ostrich's sternum is flat, lacking the keel to which wing muscles attach in flying birds. The beak is flat and broad, with a rounded tip. Like all ratites, the ostrich has no crop, and it also lacks a gallbladder. They have three stomachs, and the caecum is 71 cm (28 in) long. Unlike all other living birds, the ostrich secretes urine separately from faeces. All other birds store the urine and faeces combined in the coprodeum, but the ostrich stores the faeces in the terminal rectum.[15] They also have unique pubic bones that are fused to hold their gut. Unlike most birds, the males have a copulatory organ, which is retractable and 8 in (20 cm) long. Their palate differs from other ratites in that the sphenoid and palatal bones are unconnected.
Taxonomy
The ostrich was originally described by Linnaeus in his 18th-century work, Systema Naturae under its current binomial name. Its scientific name is derived from Latin, struthio meaning "ostrich" and camelus meaning "camel", alluding to its dry habitat.
The ostrich belongs to the ratite order Struthioniformes. Other members include rheas, emus, cassowaries, moa, kiwi and the largest bird ever, the now-extinct Elephant Bird (Aepyornis). However, the classification of the ratites as a single order has always been questioned, with the alternative classification restricting the Struthioniformes to the ostrich lineage and elevating the other groups.
Subspecies
Five subspecies are recognized:
• Common Ostrich (S. camelus) complex:
o S. c. australis, Southern Ostrich, southern Africa. It is found south of the Zambezi and Cunene rivers. It is farmed for its meat, leather and feathers in the Little Karoo area of Cape Province.
o S. c. camelus, North African Ostrich, or Red-necked Ostrich, North Africa. Historically it was the most widespread subspecies, ranging from Ethiopia and Sudan in the east throughout the Sahel to Senegal and Mauritania in the west, and north to Egypt and southern Morocco, respectively. It has now disappeared from large parts of this range,[20] and it only remains in 6 of the 18 countries where it originally occurred, leading some to consider it Critically Endangered. It is the largest subspecies, at 2.74 m (9.0 ft) in height and up to 154 kilograms (340 lb) in weight. The neck is pinkish-red, the plumage of males is black and white, and the plumage of females is grey.
o S. c. massaicus, Masai Ostrich, East Africa. It has some small feathers on its head, and its neck and thighs are pink. During the mating season, the male's neck and thighs become brighter. Its range is essentially limited to southern Kenya and eastern Tanzania and Ethiopia and parts of Southern Somalia.
o S. c. syriacus, Arabian Ostrich or Middle Eastern Ostrich, Middle East. Was formerly very common in the Arabian Peninsula, Syria, and Iraq; it became extinct around 1966.
o S. c. molybdophanes, Somali Ostrich, southern Ethiopia, northeastern Kenya, and Somalia.The neck and thighs are grey-blue, and during the mating season, the male's neck and thighs become brighter and bluer. The females are more brown than those of other subspecies. It generally lives in pairs or alone, rather than in flocks. Its range overlaps with S. c. massaicus in northeastern Kenya.
Some analyses indicate that the Somali Ostrich may be better considered a full species, but there is no consensus among experts about this. The Tree of Life Project and IOC recognize it as a different species, but The Clements Checklist of Birds of the World, Howard and Moore Complete Checklist of the Birds of the World and BirdLife International do not. As of 2010 BirdLife International is reviewing the proposed split.[1] Mitochondrial DNA haplotype comparisons suggest that it diverged from the other ostriches not quite four mya due to formation of the East African Rift. Hybridization with the subspecies that evolved southwestwards of its range, S. c. massaicus, has apparently been prevented from occurring on a significant scale by ecological separation, the Somali Ostrich preferring bushland where it browses middle-height vegetation for food while the Masai Ostrich is, like the other subspecies, a grazing bird of the open savanna and miombo habitat.
The population from Río de Oro was once separated as Struthio camelus spatzi because its eggshell pores were shaped like a teardrop and not round. However, as there is considerable variation of this character and there were no other differences between these birds and adjacent populations of S. c. camelus, the separation is no longer considered valid. This population disappeared in the latter half of the 20th century. There were 19th-century reports of the existence of small ostriches in North Africa; these are referred to as Levaillant's Ostrich (Struthio bidactylus) but remain a hypothetical form not supported by material evidence.
Evolution
The earliest fossil of ostrich-like birds is the Palaeotis living near the Asiatic steppes from the Middle Eocene, a mid-sized flightless bird that was originally believed to be a bustard. Apart from this enigmatic bird, the fossil record of the ostriches continues with several species of the modern genus Struthio which are known from the Early Miocene onwards. While the relationship of the African species is comparatively straightforward, a large number of Asian species of ostrich have been described from fragmentary remains, and their interrelationships and how they relate to the African Ostriches are confusing. In China, ostriches are known to have become extinct only around or even after the end of the last ice age; images of ostriches have been found there on prehistoric pottery and petroglyphs.
Several of these fossil forms are ichnotaxa (that is, classified according to the organism's footprints or other trace rather than its body) and their association with those described from distinctive bones is contentious and in need of revision pending more good material.
• Struthio coppensi (Early Miocene of Elizabethfeld, Namibia)
• Struthio linxiaensis (Liushu Late Miocene of Yangwapuzijifang, China)
• Struthio orlovi (Late Miocene of Moldavia)
• Struthio karingarabensis (Late Miocene – Early Pliocene of SW and CE Africa) – oospecies
• Struthio karatheodoris (Late Miocene of Greece and Bulgaria)
• Struthio kakesiensis (Laetolil Early Pliocene of Laetoli, Tanzania) – oospecies
• Struthio wimani (Early Pliocene of China and Mongolia)
• Struthio daberasensis (Early – Middle Pliocene of Namibia) – oospecies
• Struthio brachydactylus (Pliocene of Ukraine)
• Struthio chersonensis (Pliocene of SE Europe to WC Asia) – oospecies
• Asian Ostrich, Struthio asiaticus (Early Pliocene – Late Pleistocene of Central Asia to China and Morocco)
• Giant Ostrich, Struthio dmanisensis (Late Pliocene/Early Pleistocene of Dmanisi, Georgia)
• Struthio oldawayi (Early Pleistocene of Tanzania) – probably subspecies of S. camelus
• Struthio anderssoni – oospecies
Distribution and habitat
Ostriches formerly occupied Africa north and south of the Sahara, East Africa, Africa south of the rain forest belt, and much of Asia Minor. Today ostriches prefer open land and are native to the savannas and Sahel of Africa, both north and south of the equatorial forest zone. In Southwest Africa they inhabit the semi-desert or true desert. They rarely go above 100 m (330 ft). Farmed ostriches in Australia have established feral populations. The Arabian Ostriches in the Near and Middle East were hunted to extinction by the middle of the 20th century. Ostriches have occasionally been seen inhabiting islands on the Dahlak Archipelago, in the Red Sea near Eritrea.
Behaviour and ecology
Ostriches normally spend the winter months in pairs or alone. Only 16 percent of ostrich sightings were of more than two birds. During breeding season and sometimes during extreme rainless periods ostriches live in nomadic groups of five to 100 birds (led by a top hen) that often travel together with other grazing animals, such as zebras or antelopes. Ostriches are diurnal, but may be active on moonlit nights. They are most active early and late in the day. The male ostrich territory is between 2 and 20 km2 (0.77 and 7.72 sq mi).
With their acute eyesight and hearing, ostriches can sense predators such as lions from far away. When being pursued by a predator, they have been known to reach speeds in excess of 70 km/h (43 mph), and can maintain a steady speed of 50 km/h (31 mph), which makes the ostrich the world's fastest two-legged animal. When lying down and hiding from predators, the birds lay their heads and necks flat on the ground, making them appear like a mound of earth from a distance, aided by the heat haze in their hot, dry habitat.
When threatened, ostriches run away, but they can cause serious injury and death with kicks from their powerful legs. Their legs can only kick forward. Contrary to popular belief, ostriches do not bury their heads in sand to avoid danger. This myth likely began with Pliny the Elder (AD 23–79), who wrote that ostriches "imagine, when they have thrust their head and neck into a bush, that the whole of their body is concealed." This may have been a misunderstanding of their sticking their heads in the sand to swallow sand and pebbles, or, as National Geographic suggests, of the defensive behavior of lying low, so that they may appear from a distance to have their head buried.
Feeding
They mainly feed on seeds, shrubs, grass, fruit and flowers; occasionally they also eat insects such as locusts. Lacking teeth, they swallow pebbles that act as gastroliths to grind food in the gizzard. When eating, they will fill their gullet with food, which is in turn passed down their esophagus in the form of a ball called a bolus. The bolus may be as much as 210 ml (7.1 US fl oz). After passing through the neck (there is no crop) the food enters the gizzard and is worked on by the aforementioned pebbles. The gizzard can hold as much as 1,300 g (46 oz), of which up to 45% may be sand and pebbles. Ostriches can go without drinking for several days, using metabolic water and moisture in ingested plants, but they enjoy liquid water and frequently take baths where it is available. They can survive losing up to 25% of their body weight through dehydration.
Mating
Ostriches become sexually mature when they are 2 to 4 years old; females mature about six months earlier than males. As with other birds, an individual may reproduce several times over its lifetime. The mating season begins in March or April and ends sometime before September. The mating process differs in different geographical regions. Territorial males typically boom in defence of their territory and harem of two to seven hens; the successful male may then mate with several females in the area, but will only form a pair bond with a 'major' female.
The cock performs with his wings, alternating wing beats, until he attracts a mate. They will go to the mating area and he will maintain privacy by driving away all intruders. They graze until their behaviour is synchronized, then the feeding becomes secondary and the process takes on a ritualistic appearance. The cock will then excitedly flap alternate wings again, and start poking on the ground with his bill. He will then violently flap his wings to symbolically clear out a nest in the soil. Then, while the hen runs a circle around him with lowered wings, he will wind his head in a spiral motion. She will drop to the ground and he will mount for copulation. Ostriches raised entirely by humans may direct their courtship behaviour not at other ostriches, but toward their human keepers.
The female ostrich lays her fertilised eggs in a single communal nest, a simple pit, 30–60 cm (12–24 in) deep and 3 m (9.8 ft) wide, scraped in the ground by the male. The dominant female lays her eggs first, and when it is time to cover them for incubation she discards extra eggs from the weaker females, leaving about 20 in most cases. A female ostrich can distinguish her own eggs from the others in a communal nest. Ostrich eggs are the largest of all eggs, though they are actually the smallest eggs relative to the size of the adult bird — on average they are 15 cm (5.9 in) long, 13 cm (5.1 in) wide, and weigh 1.4 kilograms (3.1 lb), over 20 times the weight of a chicken's egg and only 1 to 4% the size of the female. They are glossy cream-coloured, with thick shells marked by small pits. The eggs are incubated by the females by day and by the males by night. This uses the colouration of the two sexes to escape detection of the nest, as the drab female blends in with the sand, while the black male is nearly undetectable in the night. The incubation period is 35 to 45 days, which is rather short compared to other ratites. This is believed to be the case due to the high rate of predation. Typically, the male defends the hatchlings and teaches them to feed, although males and females cooperate in rearing chicks. Fewer than 10% of nests survive the 9 week period of laying and incubation, and of the surviving chicks, only 15% of those survive to 1 year of age. However, among those ostriches who survive to adulthood, the species is one of the longest-living bird species. Ostriches in captivity have lived to 62 years and 7 months.
Predators
As a flightless species in the rich biozone of the African savanna, the ostrich must face a variety of formidable predators throughout its life cycle. Animals that prey on ostriches of all ages may include cheetahs, lions, leopards, African hunting dogs, and spotted hyena. Ostriches can often outrun most of their predators in a pursuit, so most predators will try to ambush an unsuspecting bird using obstructing vegetation or other objects. A notable exception is the cheetah, which is the most prolific predator of adult ostriches due to its own great running speeds.
Common predators of nests and young ostriches include jackals, various birds of prey, warthogs, mongoose and Egyptian vultures. If the nest or young are threatened, either or both of the parents may create a distraction, feigning injury. However, they may sometimes fiercely fight predators, especially when chicks are being defended, and have been capable of killing even their largest enemies, the lions, in such confrontations.
Physiology
Anatomy
Morphology of the ostrich lung indicates that the structure conforms to that of the other avian species, but still retains parts of its primitive avian species, ratite, structure. The opening to the respiratory pathway begins with the laryngeal cavity lying posterior to the choanae within the buccal cavity.[48] The tip of the tongue then lies anterior to the choanae, excluding the nasal respiratory pathway from the buccal cavity. The trachea lies ventrally to the cervical vertebrae extending from the larynx to the syrinx, where the trachea enters the thorax, dividing into two primary bronchi, one to each lung, in which they continue directly through to become mesobronchi. Ten different air sacs attach to the lungs to form areas for respiration. The most posterior air sacs (abdominal and post-thoracic) differ in that the right abdominal air sac is relatively small, lying to the right of the mesentery, and dorsally to the liver. While the left abdominal air sac is large and lies to the left of the mesentery.[48] The connection from the main mesobronchi to the more anterior air sacs including the interclavicular, lateral clavicular, and pre-thoracic sacs known as the ventrobronchi region. While the caudal end of the mesobronchus branches into several dorsobronchi. Together, the ventrobronchi and dorsobronchi are connected by intra-pulmonary airways, the parabronchi, which form an arcade structure within the lung called the paleopulmo. It is the only structure found in primitive birds such as ratites. The largest air sacs found within the respiratory system are those of the post-thoracic region, while the others decrease in size respectively, the interclavicular (unpaired), abdominal, pre-thoracic, and lateral clavicular sacs. The adult ostrich lung lacks connective tissue known as interparabronchial septa, which render strength to the non-compliant avian lung in other bird species. Due to this the lack of connective tissue surrounding the parabronchi and adjacent parabronchial lumen, they exchange blood capillaries or avascular epithelial plates. Like mammals, ostrich lungs contain an abundance of type II cells at gas exchange sites; an adaptation for preventing lung collapse during slight volume changes.
Function
The ostrich is a thermoregulator and maintains a body temperature of 38.1–39.7 °C in its extreme living temperature conditions, such as the heat of the savanna and desert regions of Africa. The ostrich utilizes its respiratory system via a costal pump for ventilation rather than a diaphragmatic pump as seen in most mammals. Thus, they are able to use a series of air sacs connected to the lungs. The use of air sacs forms the basis for the three main avian respiratory characteristics:
1. Air is able to flow continuously in one direction through the lung, making it more efficient than the mammalian lung.
2. It provides birds with a large residual volume, allowing them to breathe much more slowly and deeply than a mammal of the same body mass.
3. It provides a large source of air that is used not only for gaseous exchange, but also for the transfer of heat by evaporation.
Inhalation begins at the mouth and the nostrils located at the front of the beak. The air then flows through the anatomical dead space of a highly vascular trachea (~78 cm) and expansive bronchial system, where it is further conducted to the posterior air sacs. Air flow through the parabronchi of the paleopulmo is in the same direction to the dorsobronchi during inspiration and expiration. Inspired air moves into the respiratory system as a result of the expansion of thoraco abdominal cavity; controlled by inspiratory muscles. During expiration, oxygen poor air flows to the anterior air sacs and is expelled by the action of the expiratory muscles. The ostrich air sacs play a key role in respiration since they are capacious, and increase surface area (as described by the Fick Principle). The oxygen rich air flows unidirectionally across the respiratory surface of the lungs; providing the blood that has a crosscurrent flow with a high concentration of oxygen.
To compensate for the large “dead” space, the ostrich trachea lacks valves to allow faster inspiratory air flow. In addition, the total lung capacity of the respiratory system, (including the lungs and ten air sacs) of a 100 kg ostrich is about 15 L, with a tidal volume ranging from 1.2 to 1.5 L. The tidal volume is seen to double resulting in a 16-fold increase in ventilation. Overall, ostrich respiration can be thought of as a high velocity-low pressure system. At rest, there is small pressure differences between the ostrich air sacs and the atmosphere, suggesting simultaneous filling and emptying of the air sacs.
The increase in respiration rate from the low range to the high range is sudden and occurs in response to hyperthermia. Birds lack sweat glands, so when placed under stress due to heat, they heavily rely upon increased evaporation from the respiratory system for heat transfer. This rise in respiration rate however is not necessarily associated with a greater rate of oxygen consumption. Therefore, unlike other birds, the ostrich is able to dissipate heat through panting without experiencing respiratory alkalosis by modifying ventilation of the respiratory medium. During hyperpnea ostriches pant at a respiratory rate of 40–60 cycles/minute, versus their resting rate of 6–12 cycles/minute. Hot, dry and moisture lacking properties of the ostrich respiratory medium affects oxygen's diffusion rate (Henry's Law).
Ostriches develop via Intussusceptive angiogenesis, a mechanism of blood vessel formation, characterizing many organs. It is not only involved in vasculature expansion, but also in angioadaptation of vessels to meet physiological requirements. The use of such mechanisms demonstrates an increase in the later stages of lung development, along with elaborate parabronchial vasculature, and reorientation of the gas exchange blood capillaries to establish the crosscurrent system at the blood-gas barrier. The blood–gas barrier (BGB) of their lung tissue is thick. The advantage of this thick barrier may be protection from damage by large volumes of blood flow in times of activity, such as running, since air is pumped by the air sacs rather than the lung itself. As a result the capillaries in the parabronchi have thinner walls, permitting more efficient gaseous exchange. In combination with separate pulmonary and systemic circulatory systems, it helps to reduce stress on the BGB.
Circulation
Heart Anatomy
The ostrich heart is a closed system, contractile chamber. It is composed of myogenic muscular tissue associated with heart contraction features. There is a double circulatory plan in place possessing both a pulmonary circuit and systemic circuit.
The ostrich’s heart has similar features to other avian species like having a conically shaped heart, and being enclosed by a pericardium layer. Moreover, similarities also include a larger right atrium volume, and a thicker left ventricle to fulfil the systemic circuit. The ostrich heart has three features that are absent in related birds:
1. The right atrioventricular valve is fixed to the interventricular septum, by a thick muscular stock, which prevents back-flow of blood into the atrium when ventricular systole is occurring. In the fowl this valve is only connected by a short septal attachment.
2. Pulmonary veins attach to the left atrium separately, and also the opening to the pulmonary veins are separated by a septum.
3. moderator bands, full of purkinje fibers, are found in different locations in the left and right ventricles. These bands are associated with contractions of the heart and suggests this difference causes the left ventricle to contract harder to create more pressure for a completed circulation of blood around the body.
The atrioventricular node position differs from other fowl. It is located in the endocardium of the atrial surface of the right atrioventricular valve. It is not covered by connective tissue, which is characteristic of vertebrate heart anatomy. It also contains fewer myofibrils than usual myocardial cells. The AV node connects the atrial and ventricular chambers. It functions to carry the electrical impulse from the atria to the ventricle. Upon view, the myocardial cells are observed to have large densely packed chromosomes within the nucleus.
The coronary arteries start in the right and left aortic sinus and provide blood to the heart muscle in a similar fashion to most other vertebrates. Other domestic birds capable of flight have three or more coronary arteries that supply blood to the heart muscle. The blood supply by the coronary arteries are fashioned starting as a large branch over the surface of the heart. It then moves along the coronary groove and continues on into the tissue as interventricular branches toward the apex of the heart. The atria, ventricles, and septum are supplied of blood by this modality. The deep branches of the coronary arteries found with in the heart tissue are small and supply the interventricular and right atrioventricular valve with blood nutrients for which to carry out their processes. The interatrial artery of the ostrich is small in size and exclusively supplies blood to only part of the left auricle and interatrial septum.
These purkinje fibers (p-fibers) found in the hearts moderator bands are a specialized cardiac muscle fiber that causes the heart to contract. The purkinje cells are mostly found within both the endocardium and the sub-endocardium. The sinoatrial node shows a small concentration of purkinje fibers, however, continuing through the conducting pathway of the heart the bundle of his shows the highest amount of these purkinje fibers.
Blood composition
The red blood cell count per unit volume in the ostrich is about 40% of that of a human; however, the red blood cells of the ostrich are about three times larger than the red blood cells of a human. The blood oxygen affinity, known as P50, is higher than that of both humans and similar avian species. The reason for this decreased oxygen affinity is due to the hemoglobin configuration found in the ostrich blood. The ostrich’s tetramer is composed of hemoglobin type A and D, compared to typical mammalian tetramers composed of hemoglobin type A and B; hemoglobin D configuration causes a decreased oxygen affinity at the site of the respiratory surface.
During the embryonic stage Hemoglobin E is present. This subtype increases oxygen affinity in order to transport oxygen across the allantoic membrane of the embryo. This can be attributed to the high metabolic need of the developing embryo, thus high oxygen affinity serves to satisfy this demand. When the chick hatches hemoglobin E diminishes while hemoglobin A and D increase in concentration. This shift in hemoglobin concentration results in both decreased oxygen affinity and increased P50 value.
Furthermore, the P50 value is influenced by differing organic modulators. In the typical mammalian RBC 2,3 – DPG causes a lower affinity for oxygen. 2,3- DPG constitutes approximately 42–47%, of the cells phosphate of the embryonic ostrich. However, the adult ostrich have no traceable 2,3- DPG.In place of 2,3-DPG the ostrich uses inositol polyphosphates (IPP), which vary from 1–6 phosphates per molecule.[60] In relation to the IPP, the ostrich also uses ATP to lower oxygen affinity. ATP has a consistent concentration of phosphate in the cell. Around 31% at incubation periods, and dropping to 16–20% in 36 day old chicks. However, IPP has low concentrations, around 4%, of total phosphate concentration in embryonic stages; However, the IPP concentration jumps to 60% of total phosphate of the cell. The majority of phosphate concentration switches from 2,3- DPG to IPP, suggesting the result of the overall low oxygen affinity is due to these varying polyphosphates.
Concerning immunological adaptation, it was discovered that wild ostrich's have a pronounced non specific immunity defense, with blood content reflecting high values of lysosome, and phagocyte cells in medium. This is in contrast to domesticated ostriches, who in captivity develop high concentration of immunoglobulin antibodies in their circulation, indicating an acquired immunological response. It is suggested that this immunological adaptability may allow this species to have a high success rate of survival in variable environmental settings.
Osmoregulation
Physiological challenges
The ostrich is an xeric animal, due to the fact that it lives in habitats that are both dry and hot. Water is scarce in dry and hot environment, and this poses a challenge to the ostrich's water consumption. Also the ostrich is a ground bird and cannot fly to find water sources, which poses a further challenge. Because of their size, ostriches cannot easily escape the heat of their environment; however, they dehydrate less than their small bird counterparts because of their large surface area to volume ratio. Hot, arid habitats pose osmotic stress, such as dehydration, which triggers the ostrich’s homeostatic response to osmoregulate.
System overview
The ostrich is well adapted to hot, arid environments through specialization of excretory organs. The ostrich has an extremely long and developed colon the length of approximately 11-13m between the coprodeum and the paired caeca, which are around 80 cm long. A well developed caeca is also found and in combination with the rectum forms the microbial fermentation chambers used for carbohydrate breakdown. The catabolism of carbohydrates produces ~ 0.56 g of water that can be used internally. The majority of their urine is stored in the coprodeum, and the faeces are separately stored in the terminal colon. The coprodeum is located ventral to the terminal rectum and urodeum (where the ureters open). Found between the terminal rectum and coprodeum is a strong sphincter. The coprodeum and cloaca are the main osmoregulatory mechanisms used for the regulation and reabsorption of ions and water, or net water conservation. As expected in a species inhabiting arid regions, dehydration causes a reduction in faecal water, or dry feces. This reduction is believed to be caused by high levels of plasma aldosterone, which leads to rectal absorption of sodium and water. Also expected is the production of hyperosmotic urine; cloacal urine has been found to be 800 mosmol/L. The U:P (urine:plasma) ratio of the ostrich is therefore greater than one. Diffusion of water to the coprodeum (where urine is stored) from plasma across the epithelium is voided. This void is believed to be caused by the thick mucosal layering of the coprodeum.
Ostriches have two kidneys, which are chocolate brown in color, granular in texture, and lie in a depression in the pelvic cavity of the dorsal wall. They are covered by peritoneum and a layer of fat. Each kidney is about 300 mm long, 70 mm wide, and divided into a cranial, middle, and caudal sections by large veins.[48] The caudal section is the largest, extends into the middle of the pelvis. The ureters leave the ventral caudomedial surface and continue caudally, near the midline into the opening of the urodeum of the cloaca. Although there is no bladder, a dilated pouch of ureter stores the urine until it is secreted continuously down from the ureters to the urodeum until discharged.
Kidney function
Ostrich kidneys are fairly large, and so are able to hold significant amounts of solutes. Hence, ostriches drink relatively large volumes of water daily, and excrete generous quantities of highly concentrated urine. It is when drinking water is unavailable or withdrawn, that the urine becomes highly concentrated with uric acid and urates. It seems that ostriches who normally drink relatively large amounts of water tend to rely on renal conservation of water when drinking water is scarce within the kidney system. Though there have been no official detailed renal studies conducted on the flow rate (Poiseuille's Law) and composition of the ureteral urine in the ostrich, knowledge of renal function has been based on samples of cloacal urine, and samples or quantitative collections of voided urine. Studies have shown that the amount of water intake, and dehydration impacts the plasma osmolality and urine osmolality within various sized ostriches. During a normal hydration state of the kidneys, young ostriches tend to have a measured plasma osmolality of 284 mOsm, and urine osmolality of 62 mOsm. Adults have higher rates with a plasma osmolality of 330 mOsm, and a urine osmolality of 163 mOsm. The osmolality of both plasma and urine can alter in regards to whether there is an excess or depleted amount of water present within the kidneys. An interesting fact of ostriches is that when water is freely available, the urine osmolality can reduce to 60–70 mOsm, not losing any necessary solutes from the kidneys when excess water is excreted. Dehydrated or salt-loaded ostriches can reach a maximal urine osmolality of approximately 800 mOsm. When the plasma osmolality has been measured simultaneously with the maximal osmotic urine, it is seen that the urine:plasma ratio is 2.6:1, the highest encountered among avian species.[48] Along with dehydration, there is also a reduction in flow rate from 20 L/day to only a mere 0.3–0.5 L/day.
In mammals and ostriches, the increase of the glomerular filtration rate (GFR) and urine flow rate (UFR) is due to a high protein diets. As seen in various studies, scientists have measured clearance of creatinine, a fairly reliable marker of glomerular filtration rate (GFR). It has been seen that during normal hydration within the kidneys, the glomerular filtration rate is approximately 92 ml/min. However, when an ostrich experiences dehydration for at least 48 hours (2 days), this value diminishes to only a mere 25% of the hydrated GFR rate. Thus in response to the dehydration, ostrich kidneys secrete small amounts of very viscous glomerular filtrates that have not been broken down, and return them to the circulatory system through blood vessels. The reduction of GFR during dehydration is extremely high, and so the fractional excretion of water (urine flow rate as a percentage of GFR) drops down from 15% at normal hydration to 1% during dehydration.
Water intake and turnover
Ostriches employ adaptive features to manage the dry heat and solar radiation in their habitat. Ostriches will drink available water; however, they are limited in accessing water by being flightless. They are also able to harvest water through dietary means, consuming plants such as the Euphorbia heterochroma that hold up to 87% water.
Water mass accounts for 68% of body mass in adult ostriches; this is down from 84% water mass in 35-day-old chicks. The differing degrees of water retention are thought to be a result of varying body fat mass. In comparison to smaller birds ostriches have a lower evaporative water loss resulting from their small body surface area per unit weight.
When heat stress is at its maximum, ostriches are able to recover evaporative loss by using a metabolic water mechanism to counter the loss by urine, feces, and respiratory evaporation. An experiment to determine the primary source of water intake in the ostrich indicated that while the ostrich does employ a metabolic water production mechanism as a source of hydration, the most important source of water is food. When ostriches were restricted to the no food or water condition, the metabolic water production was only 0.5 L/day ^-1, while total water lost to urine, feces and evaporation was 2.3 L/day^-1. When the birds were given both water and food, total water gain was 8.5 L/day ^-1. In the food only condition total water gain was 10.1 /day^-1. These results show that the metabolic water mechanism is not able to sustain water loss independently, and that food intake, specifically of plants with a high water content such as Euphorbia heterochroma, is necessary to overcome water loss challenges in the ostrich's arid habitat.
In times of water deprivation, urine electrolyte and osmotic concentration increases while urination rate decreases. Under these conditions Urine solute:Plasma[disambiguation needed] solute ratio is approximately 2.5, or hyperosmotic; that is to say that the ratio of solutes to water in the plasma is shifted down whereby reducing osmotic pressure in the plasma. Water is then able to be held back from excretion, keeping the ostrich hydrated, while the passed urine contains higher concentrations of solute. This mechanism exemplifies how renal function facilitates water retention during periods of dehydration stress.
Nasal glands
A number of avian species use nasal salt glands, alongside their kidneys, to control hypertonicity in their blood plasma. However, the ostrich shows no nasal glandular function in regard to this homeostatic process. Even in a state of dehydration, which increases the osmolality of the blood, nasal salt glands show no sizeable contribution of salt elimination.[66] Also, the overall mass of the glands was less than that of the duck’s nasal gland.[66] The ostrich, having a heavier body weight, should have larger, heavier nasal glands to more effectively excrete salt from a larger volume of blood, but this is not the case. These unequal proportions contribute to the assumption that the ostrich’s nasal glands do not play any role in salt excretion. The nasal glands may be the result of an ancestral trait, which is no longer needed by the ostrich, but has not been bred out of their gene pool.
Biochemistry
The majority of the ostrich’s internal solutes are made up of sodium ions (Na+), potassium ions (K+), chloride ions (Cl-), total short-chain fatty acids (SCFA), and acetate. The caecum contains a high water concentration with reduced levels nearing the terminal colon, and exhibits a rapid fall in Na+ concentrations and small changes in K+ and Cl-. The colon is divided into three sections and take part in solute absorption. The upper colon largely absorbs Na+ and SCFA, and partially absorbs KCl. The middle colon absorbs Na+, SCFA, with little net transfer of K+ and Cl-. The lower colon then slightly absorbs Na+ and water, and secretes K+. There is no net movements of Cl- and SCFA found in the lower colon.
When the ostrich is in a dehydrated state plasma osmolality, Na+, K+, and Cl- ions all increase, however, K+ ions returned to controlled concentration. The ostrich also experiences an increase in haematocrit, resulting in a hypovolemic state. Two antidiuretic hormones, Arginine vasotocin (AVT) and angiotensin (AII) are increased in blood plasma as a response to hyperosmolality and hypovolemia. AVT triggers antidiuretic hormone (ADH) which targets the nephrons of the kidney. ADH causes a reabsorption of water from the lumen of the nephron to the extracellular fluid osmotically. These extracellular fluids then drain into blood vessels, causing a rehydrating effect. This drainage prevents loss of water by both lowering volume and increasing concentration of the urine. Angiotensin, on the other hand, causes vasoconstriction on the systemic arterioles, and acts as a dipsogen for ostriches. Both of these antidiuretic hormones work together to maintain water levels in the body that would normally be lost due to the osmotic stress of the arid environment.
The end-product of catabolism of protein metabolism in animals is nitrogen. Animals must excrete this in the form of nitrogenous compounds. Ostriches are uricotelic. They excrete nitrogen as the complex nitrogenous waste compound uric acid, and related derivatives. Uric acid's low solubility in water gives a semi-solid paste consistency to the ostrich's nitrogenous waste.
Thermoregulation
Ostriches are homeothermic endotherms; they regulate a constant body temperature via regulating their metabolic heat rate. They closely regulate their core body temperature, but their appendages may be cooler in comparison as found with regulating species. The temperature of their beak, neck surfaces, lower legs, feet and toes are regulated through heat exchange with the environment. Up to 40% of their produced metabolic heat is dissipated across these structures, which account for about 12% of their total surface area. Total evaporative water loss (TEWL) is statistically lower in the ostrich than in membering ratites.
As ambient temperature increases, dry heat loss decreases, but evaporative heat loss increases because of increased respiration. As ostriches experience high ambient temperatures, ~50 °C, they become slightly hyperthermic; however, they can maintain a stable body temperature, ~40 °C, for up to 8 hours in these conditions. When dehydrated, the ostrich minimises water loss, causing the body temperature to increase further. When the body heat is allowed to increase the temperature gradient between the ostrich and ambient heat is equilibrated.
Physical adaptations
Ostriches have developed a comprehensive set of behavioural adaptations for thermoregulation, such as altering their feathers. Ostriches display a feather fluffing behaviour that aids them in thermoregulation by regulating convective heat loss at high ambient temperatures. They may also physically seek out shade in times of high ambient temperatures. When feather fluffing, they contract their muscles to raise their feathers to increase the air space next to their skin. This air space provides an insulating thickness of 7 cm. The ostrich will also expose the thermal windows of their unfeathered skin to enhance convective and radiative loss in times of heat stress. At higher ambient temperatures lower appendage temperature increases to 5 °C difference from ambient temperature. Neck surfaces are around 6–7 °C difference at most ambient temperatures, except when temperatures are around 25 °C, it was only 4 °C above ambient.
At low ambient temperatures the ostrich utilizes feather flattening, which conserves body heat through insulation. The low conductance coefficient of air allows less heat to be lost to the environment. This flattening behavior compensate for ostrich's rather poor cutaneous evaporative water loss (CEWL). These feather heavy areas such as the body, thighs and wings do not usually vary much from ambient temperatures due to this behavioural controls. This ostrich will also cover its legs to reduce heat loss to the environment, along with undergoing piloerection and shivering when faced with low ambient temperatures.
Internal adaptations
The use of countercurrent heat exchange with blood flow allows for regulated conservation/ elimination of heat of appendages. When ambient temperatures are low, heterotherms will constrict their arterioles to reduce heat loss along skin surfaces. The reverse occurs at high ambient temperatures, arterioles dilate to increase heat loss.
At ambient temperatures below their body temperatures (thermal neutral zone (TNZ)), ostriches decrease body surface temperatures so that heat loss occurs only across about 10% of total surface area. This 10% include critical areas that require blood flow to remain high to prevent freezing, such as their eyes. Their eyes and ears tend to be the warmest regions. It has been found that temperatures of lower appendages were no more than 2.5 °C above ambient temperature, which minimizes heat exchange between feet, toes, wings, and legs.
Both the Gular and air sacs, being close to body temperature, are the main contributors to heat and water loss. Surface temperature can be affected by the rate of blood flow to a certain area, and also by the surface area of the surrounding tissue. The Ostrich reduces blood flow to the trachea to cool itself, and vasodilates its blood vessels around the gular region to raise the temperature of the tissue. The air sacs are poorly vascularized but show an increased temperature, which aids in heat loss.
Ostriches have evolved a 'selective brain cooling' mechanism as a means of thermoregulation. This modality allows the ostrich to manage the temperature of the blood going to the brain in response to the extreme ambient temperature of the surroundings. The morphology for heat exchange occurs via cerebral arteries and the ophthalmic rete, a network of arteries originating from the ophthalmic artery. The ophthalmic rete is analogous to the carotid rete found in mammals, as it also facilitates transfer of heat from arterial blood coming from the core to venous blood returning from the evaporative surfaces at the head.
Researchers suggest that ostriches also employ a ‘selective brain warming’ mechanism in response to cooler surrounding temperatures in the evenings. The brain was found to maintain a warmer temperature when compared to carotid arterial blood supply. Researchers hypothesize three mechanisms for this finding. They first suggest a possible increase in metabolic heat production within the brain tissue itself to compensate for the colder arterial blood arriving from the core. They also speculate that there is an overall decrease in cerebral blood flow to the brain. Finally, they suggest that warm venous blood perfusion at the ophthalmic rete facilitates warming of cerebral blood that supplies the hypothalamus. Further research will need to be done to find how this occurs.
Breathing adaptations
The ostrich has no sweat glands, and under heat stress they rely on panting to reduce their body temperature. Panting increases evaporative heat (and water) loss from its respiratory surfaces, therefore forcing air and heat removal without the loss of metabolic salts. Panting allows the ostrich to have a very effective respiratory evaporative water loss (REWL). Heat dissipated by respiratory evaporation increases linearly with ambient temperature, matching the rate of heat production. As a result of panting the ostrich should eventually experience alkalosis. However, The CO2 concentration in the blood does not change when hot ambient temperatures are experienced. This effect is caused by a lung surface shunt. The lung is not completely shunted, allowing enough oxygen to fulfill the bird’s metabolic needs. The ostrich utilizes gular fluttering, rapid rhythmic contraction and relaxation of throat muscles, in a similar way to panting. Both these behaviors allow the ostrich to actively increase the rate of evaporative cooling.
In hot temperatures water is lost via respiration. Moreover, varying surface temperatures within the respiratory tract contribute differently to overall heat and water loss through panting. The surface temperature of the gular area is 38 °C; that of the tracheal area, between 34 °C and 36 °C; and that of both anterior and posterior air sacs, 38 °C. The long trachea, being cooler than body temperature, is a site of water evaporation.
As ambient air becomes hotter, additional evaporation can take place lower in the trachea making its way to the posterior sacs, shunting the lung surface. The trachea acts as a buffer for evaporation because of the length, and the controlled vascularization. The Gular is also heavily vascularized; its purpose is for cooling blood, but also evaporation, as previously stated. Air flowing through the trachea can be either laminar or turbulent depending on the state of the bird. When the ostrich is breathing normally, under no heat stress, air flow is laminar. When the ostrich is experiencing heat stress from the environment the air flow is considered turbulent. This suggests that laminar air flow causes little to no heat transfer, while under heat stress turbulent airflow can cause maximum heat transfer within the trachea.
Development
Ostrich embryos during development transition from ectotherms to endotherms. This change requires an increase in energy production or ATP. Research has found that increased phosphorylation of AMP activated protein kinase is part of a positive feedback mechanism influencing an increase of transcription factor concentrations that facilitate an increase of mitochondrial biosynthesis. Part of the mechanism behind the increase in mitochondrial abundance has been described here and is a key factor in transitioning from an ectotherm to an endotherm for these developing chicks.
Metabolism
Ostriches are able to attain their necessary energetic requirements via the oxidation of absorbed nutrients. Much of the metabolic rate in animals is dependent upon their allometry, the relationship between body size to shape, anatomy, physiology and behaviour of an animal. Hence, it is plausible to state that metabolic rate in animals with larger masses is greater than animals with a smaller mass.
When a bird is inactive, unfed, and the ambient temperature (i.e. in the thermo-neutral zone) is high, the energy expended is at its minimum. This level of expenditure is better known as the basal metabolic rate (BMR), and can be calculated by measuring the amount of oxygen consumed during various activities. Therefore in ostriches we see use of more energy when compared to smaller birds in absolute terms, but less per unit mass.
A key point when looking at the ostrich metabolism is to note that it is a non-passerine bird. Thus, BMR in ostriches is particularly low with a value of only 0.113 ml O2 g−1 h−1. This value can further be described using Kleiber's law, which relates the BMR to the body mass of an animal.
where is body mass, and metabolic rate is measured in kcal per day.
In ostriches, a BMR (ml O2 g−1 h−1) = 389 kg0.73, describing a line parallel to the intercept with only about 60% in relation to other non-passerine birds.
Along with BMR, energy is also needed for a range of other activities. If the ambient temperature is lower than the thermo-neutral zone, heat is produced to maintain body temperature. So, the metabolic rate in a resting, unfed bird, that is producing heat is known as the standard metabolic rate (SMR) or resting metabolic rate(RMR). The ostrich SMR has been seen to be approximately 0.26 ml O2 g−1 h−1, almost 2.3 times the BMR. On another note, animals that engage in extensive physical activity employ substantial amounts of energy for power. This is known as the maximum metabolic scope. In an ostrich, it is seen to be at least 28 times greater than the BMR. Likewise, the daily energy turnover rate for an ostrich with access to free water is 12,700 kJ day−1, equivalent to 0.26 ml O2 g−1 h−1.
Status and conservation
The wild ostrich population has declined drastically in the last 200 years, with most surviving birds in reserves or on farms. However, its range remains very large (9,800,000 square kilometres (3,800,000 sq mi)), leading the IUCN and BirdLife International to treat it as a species of Least Concern.[1] Of its 5 subspecies, the Middle Eastern Ostrich (S. c. syriacus) became extinct around 1966, and the North African Ostrich (S. c. camelus) has declined to the point where it now is included on CITES Appendix I and some treat it as Critically Endangered.
Ostriches and humans
Ostriches have inspired cultures and civilizations for 5,000 years in Mesopotamia and Egypt. A statue of Arsinoe II of Egypt riding an ostrich was found in a tomb in Egypt. The Kalahari bushmen still use their eggs as water jugs.
Hunter-gatherers in the Kalahari use ostrich eggshells as water containers in which they puncture a hole to enable them to be used as canteens. The presence of such eggshells with engraved hatched symbols dating from the Howiesons Poort period of the Middle Stone Age at Diepkloof Rock Shelter in South Africa suggests ostriches were an important part of human life as early as 60,000 BP.
Hunting and farming
In Roman times, there was a demand for ostriches to use in venatio games or cooking. They have been hunted and farmed for their feathers, which at various times have been popular for ornamentation in fashionable clothing (such as hats during the 19th century). Their skins are valued for their leather. In the 18th century they were almost hunted to extinction; farming for feathers began in the 19th century. At the start of the 20th century there were over 700,000 birds in captivity. The market for feathers collapsed after World War I, but commercial farming for feathers and later for skins and meat became widespread during the 1970s. Ostriches are so adaptable that they can be farmed in climates ranging from South Africa to Alaska.
Ostriches were farmed for their feathers in South Africa beginning in the 19th century. According to Frank G. Carpenter, the English are credited with first taming ostriches outside Cape Town. Farmers captured baby ostriches and raised them successfully on their property, and were able to obtain a crop of feathers every seven to eight months instead of killing wild ostriches for their feathers.
It is claimed that ostriches produce the strongest commercial leather. Ostrich meat tastes similar to lean beef and is low in fat and cholesterol, as well as high in calcium, protein and iron. Uncooked, it is dark red or cherry red, a little darker than beef.
Attacks
Ostriches typically avoid humans in the wild, since they correctly assess humans as potential predators, and, if approached, often run away. However, ostriches may turn aggressive rather than run when threatened, especially when cornered, and may also attack when they feel the need to defend their offspring or territories. Similar behaviors are noted in captive or domesticated ostriches, which retain the same natural instincts and can occasionally respond aggressively to stress. When attacking a person, ostriches kick forward with their powerful feet, armed with long claws, which are capable of disemboweling or killing a person with a single blow. In one study of ostrich attacks, it was estimated that two to three attacks that result in serious injury or death occur each year in the area of Oudtshoorn, South Africa, where a large number of ostrich farms are set next to both feral and wild ostrich populations.
Racing
In some countries, people race each other on the backs of ostriches. The practice is common in Africa and is relatively unusual elsewhere. The ostriches are ridden in the same way as horses with special saddles, reins, and bits. However, they are harder to manage than horses.
The racing is also a part of modern South African culture. Within the United States, a tourist attraction in Jacksonville, Florida called 'The Ostrich Farm' opened up in 1892; it and its races became one of the most famous early attractions in the history of Florida.
In the United States, Chandler, Arizona hosts the annual 'Ostrich Festival' which features ostrich races. Racing has also occurred at many other locations such as Virginia City in Nevada, Canterbury Park in Minnesota, Prairie Meadows in Iowa, and Ellis Park in Kentucky.
The Tsessebe
The common tsessebe or sassaby (Damaliscus lunatus) is one of five species of the subfamily Alcelaphinae in the family Bovidae. It is most closely related to the topi and the bontebok in the same genus. Tsessebe are found primarily in Angola, Zambia, Namibia, Botswana, Zimbabwe, Swaziland, and South Africa. They used to be spread throughout a significant area of Africa, from Senegal to eastern Ethiopia south to the northern areas of South Africa. Tsessebe can run at a maximum of 80 km/h.
Appearance
Adult tsessebe are 150 to 230 cm in height. They are quite large animals, with males weighing 137 kg and females weighing 120 kg, on average. Their horns range from 37 cm for females to 40 cm for males. For males, horn size plays an important role in territory defense and mate attraction, although horn size is not positively correlated with territorial factors of mate selection. Their bodies are chestnut brown. The fronts of their faces and their tail tufts are black; the forelimbs and thigh are greyish or bluish-black. Their hind limbs are brownish-yellow to yellow and their bellies are white. In the wild, tsessebe usually live a maximum of 15 years, but in some areas, their average lifespan is drastically decreased due to overhunting and the destruction of habitat.
Behavior
Tsessebe are social animals. Females form herds composed of six to 10, with their young. After males turn one year of age, they are ejected from the herd and form bachelor herds that can be as large as 30 young bulls. Territorial adult bulls form herds the same size as young bulls, although the formation of adult bull herds is mainly seen in the formation of a lek. Tsessebe declare their territory through a variety of behaviors. Territorial behavior includes moving in erect posture, high-stepping, defecating in a crouch stance, ground-horning, mud packing, shoulder-wiping, and grunting. The most important aggressive display of territorial dominance is in the horning of the ground. Another far more curious form of territory marking is through the anointing of their foreheads and horns with secretions from glands near their eyes. Tsessebe accomplish this by inserting grass stems into their preorbital glands to coat them with secretion, then waving it around, letting the secretions fall onto their heads and horns. This process is not as commonly seen as ground-horning, nor is its purpose as well known.
Several of their behaviors strike scientists as peculiar. One such behavior is the habit of sleeping tsessebe to rest their heads mouth down on the ground with their horns sticking straight up into the air. Male tsessebe have also been observed standing in parallel ranks with their eyes closed, bobbing their heads back and forth. These habits are peculiar because scientists have yet to find a proper explanation for their purposes or function
Diet and habitat
Tsessebe are primarily grazing herbivores in grasslands, open plains, and lightly wooded savannas, but they are also found in rolling uplands and very rarely in flat plains below 1500 m above sea level. Tsessebe found in the Serengeti usually feed in the morning between 8:00 and 9:00 am and in the afternoon after 4:00 pm. The periods before and after feeding are spent resting and digesting or watering during dry seasons. Tsessebe can travel up to 5 km to reach a viable water source. To avoid encounters with territorial males or females, tsessebe usually travel along territorial borders, though it leaves them open to attacks by lions and leopards.
Breeding and reproduction
Tsessebe reproduce at a rate of one calf per year per mating couple. Calves reach sexual maturity in two to three and half years. After mating, the gestation period of a tsessebe cow lasts seven months. The rut, or period when males start competing for females, starts in mid-February and stretches through March. The female estrous cycle is shorter, but happens in this time.
The breeding process starts with the development of a lek. Leks are established by the congregation of adult males in an area to which females visit only for the purpose of mating. Lekking is of particular interest, since female choice of a mate in the lek area is independent of any direct male influence. Several options are available to explain how females choose a mate, but the most interesting is in the way the males group in the middle of a lek. The grouping of males can appeal to females for several reasons. First, groups of males can provide protection from predators. Second, if males group in an area with a low food supply, it prevents competition between males and females for resources. Finally, the grouping of males provides females a wider variety of mates to choose from, as they are all located in one central area. Dominant males occupy the center of the leks, so females are more likely to mate at the center than at the periphery of the lek.
A study by Bro-Jorgensen (2003) allowed a closer look into lek dynamics. The closer a male is to the center of the lek, the greater his mating success rate. For a male to reach the center of the lek, he must be strong enough to outcompete other males. Once a male's territory is established in the middle of the lek, it is maintained for quite a while; even if an area opens up at the center, males rarely move to fill it unless they are able to outcompete the large males already present. However, maintaining central lek territory has many physical drawbacks. For example, males are often wounded in the process of defending their territory from hyenas and other males.
Conservation status
The population of Damaliscus lunatus was estimated to be in the tens of thousands in 1998, so it was declared at low risk of extinction. However, the IUCN Species Survival Commission observed a general population decline that would result in the population becoming vulnerable to extinction by the year 2025. Tsessebe populations once were present in much greater numbers, but populations declined due to habitat destruction, with bush encroachment playing a primary role.
The Waterbuck
Taxonomy and etymology
The scientific name of the waterbuck is Kobus ellipsiprymnus. The waterbuck is one of the six species of the genus Kobus and belongs to the family Bovidae. It was first described by Irish naturalist William Ogilby in 1833. The generic name Kobus is a New Latin word, originating from an African name, koba. The specific name ellipsiprymnus refers to the white elliptical ring on the rump. It is composed of two Greek words : ellipes, which means lacking; and prumnos, which means the hind part.
The type specimen of the waterbuck was collected by South African hunter-explorer Andrew Steedman in 1832. This specimen was named Antilope ellispiprymnus by Ogilby in 1833. This species was transferred to the genus Kobus and named K. ellipsiprymnus in 1840. In 1835, German naturalist Eduard Rüppell collected another specimen, which differed from Steedman's specimen in having a prominent white ring on its rump. Considering it a separate species, Rüppell gave it the Amharic name "defassa" waterbuck and scientific name Antilope defassa. Presently, these two are considered to be the same species, K. ellipsiprymnus.
Subspecies
37 subspecies of the waterbuck had been initially recognised on the basis of pelage colour. They classified into two groups - the Ellipsen waterbuck group and the Defassa waterbuck group. Owing to the high variability of coat colour in the Defassa waterbuck group, as many as 29 subspecies were included in it; the Ellipsen waterbuck group consisted of eight subspecies. In 1971, however, the number of subspecies was reduced to thirteen (four for the Ellipsen waterbuck group and nine Defassa waterbuck group). These subspecies are often found to interbreed in Tanzania and Kenya, where their ranges overlap extensively. Though they occur in Zambia as well, their ranges are separated by relief features or by the Muchinga escarpment. The list of subspecies is as follows:
- K. e. ellipsiprymnus (Ellipsen waterbuck) group: Found in southeast Africa, ranging from southern Somalia to KwaZulu-Natal (South Africa) and inland to the Gregory Rift and Botswana. Includes the following four subspecies:
- K. e. ellipsiprymnus Ogilby, 1833
- K. e. kondensis Matschie, 1911 (including lipuwa, kulu)
- K. e. pallidus Matschie, 1911
- K. e. thikae Matschie, 1910 (including kuru and canescens)
- K. e. defassa (Defassa waterbuck) group: Found west of the Gregory Rift, ranging from Ethiopia west to Senegal and south to Zambia. Includes the following nine subspecies:
- K. e. adolfi-friderici Matschie, 1906 (including fulvifrons, nzoiae and raineyi)
- K. e. annectens Schwarz, 1913 (includng schubotzi)
- K. e. crawshayi P. L. Sclater, 1894 (including uwendensis, frommiand münzneri)
- K. e. defassa Rüppell, 1835 (including matschiei and hawashensis)
- K. e. harnieri Murie, 1867 (including avellanifrons, ugandae, dianae, ladoensis, cottoni, breviceps, albertensis and griseotinctus)
- K. e. penricei W. Rothschild, 1895
- K. e. tjäderi Lönnberg, 1907 (including angusticeps and powelli)
- K. e. tschadensis Schwarz, 1913
- K. e. unctuosus Laurillard, 1842 (including togoensis)
The waterbuck is the largest of the kob antelopes. It is a sexually dimorphic antelope, with the males larger and heavier than the females. The head-and-body length is typically between 177–235 cm (70–93 in) and the average height is between 120 and 136 cm (47 and 54 in). Males reach approximately 127 cm (50 in) at the shoulder, while females reach 119 cm (47 in). Males typically weigh 198–262 kg (437–578 lb) and females 161–214 kg (355–472 lb). The tail is 22–45 cm (8.7–17.7 in) long.
The waterbuck is of a robust build. The shaggy coat is reddish brown to grey, and becomes progressively darker with age. Though apparently thick, the hair is sparse on the coat. The hair on the neck is, however, long and shaggy. When sexually excited, the skin of the waterbuck secretes a greasy substance, giving it the name "greasy kob". The face is marked with a white muzzle and light eyebrows and insides of the ears. There is a cream-coloured patch called "bib" on the throat. The neck is long, while the legs are short.
The long, spiral-structured horns, found only in males, sweep back and up. The first group shows a white rump patch, the second a white, ellipse-shaped ring on the rump that extends above the tail.
Habitat
Waterbuck are found in scrub and savanna areas near water, where they eat grasses. Despite their name, waterbuck do not spend much time in the water, but will take refuge there to escape predators. They are diurnal. Females gather in herds of between two and 600 individuals. Males keep territories of around 300 acres (1.2 km²) during their prime. They usually lose their territories before the age of 10.