The historical taxonomic treatment of the Plains Zebra is somewhat confusing. The Plains Zebra complex was long known as Equus burchelli, with the extinct form, the Quagga, recognized as a distinct species, E. quagga. Some evidence suggests that the ranges of the Quagga and the Plains Zebra form known as "Burchell's Zebra" (now E. quagga burchelli) overlapped in southern Africa without interbreeding. However, recent genetic analyses of both mitochondrial and nuclear DNA indicates that the genetic variation among extinct and extant Plains Zebras is no greater than that seen among modern breeds of the Domestic Horse (E. caballus). Thus, the Plains Zebra and the extinct Quagga are now treated as belonging to a single species, E. quagga.
Plains Zebras range from northern Kenya to southern Africa, with those in more southern poulations being larger and with less stripe coverage. These zebras are found in tropical, subtropical, and temperate grasslands, steppes, savannas, and woodlands. Only deserts, dense woodlands, and permanent wetlands are avoided. They occur from sea level to 4300 m (on Mount Kenya). They need to drink daily so they are never more than around half a day's travel (5 to 10 km) from a reliable water source.
Plans Zebras are true grazers and are active both day and night. As hindgut fermenters, they require large quantities of food and may spend up to 20 hours per day foraging.
Females give birth to a single offspring after a 12 month gestation period. Foals begin feeding on grass at a month, but continue to nurse for another 5 months. Females become sexually mature at two to three years. Males begin maintaining harems at around five years.
In 2002, there were an estimated 660,000 Plains Zebras. More than 75% of these are Grant's Zebras (E. q. boehmi), including around 200,000 in the Serengeti-Mara ecosystem. Although Plains Zebras appear to be well protected in much of Kenya and Tanzania, over much of their range they are threatened by poaching and habitat loss.
(Rubenstein 2011 and references therein)
- Rubenstein, D.I. 2011. Plains Zebra (Equus quagga). Pp. 141-142 in: Wilson, D.E. and Mittermeier, R.A., eds. Handbook of the Mammals of the World. Volume 2. Hoofed Mammals. Lynx Edicions, Barcelona.
The six morphologically defined subspecies are distributed as follows (following Groves and Bell 2004, and Klingel in press):
E. q. crawshaii(Crawshay’s Zebra) occurs in Zambia, east of the Luangwa River, Malawi, south-eastern Tanzania from Lake Rukwa east to Mahungoi, and Mozambique as far south as the Gorongoza district;
E. q. borensis ranges in north-west Kenya, from Guas ngishu and Lake Baringo, to the Karamoja district of Uganda and south-east Sudan, east of the Nile River to the northern limit of the species at 32°N;
E. q. boehmi (Grant’s Zebra or Boehm's Zebra) is found in Zambia, west of the Luangwa River, west to Kariba, Shaba Province of DR Congo north to Kibanzao Plateau; Tanzania north from Nyangaui and Kibwezi into south-west Uganda, south-west Kenya as far as Sotik, and east Kenya, east of the Rift Valley, into southern Ethiopia and perhaps to the Juba River in Somalia.
E. q. chapmani (Chapman's Zebra) ranges from north-east South Africa, from about 24°S, 31°E, north to Zimbabwe, west into Botswana at about 19°S, 24°E, the Caprivi Strip in Namibia, and southern Angola;
E. q. burchellii (Burchell's Zebra) formerly occurred north of the Vaal/Orange Rivers, extending north-west via southern Botswana to Etosha National Park and the Kaokoveld, south-east to KwaZulu-Natal and Swaziland. It is now extinct in the middle of its range. E.b. antiquorum is now included in this subspecies;
E. q. quagga (Quagga) occurred in the former Cape Province, south of the Orange and Vaal Rivers and west of the Drakensberg. Now extinct.
A native of southern Africa, the quagga used to occur in vast herds in the Karoo regions of Cape Province and the southern part of Orange Free State. It is now extinct. (South Africa's Threatened Wildlife, 1993)
Biogeographic Regions: neotropical (Native )
The quagga (Equus quagga) is recently extinct. It was closely related to horses and zebras. These zebras averaged 53 inches in height and weighed between 500 and 700 pounds. The Quagga was a relative of the Burchell's Zebra, Equus burchelli, and differed mainly in the degree of striping. The Burchell's Zebra has black stripes on a white background, with brownish "shadow" stripes in between. There is much variability in this pattern, and some Burchell's Zebras have virtually unstriped hindquarters. Museum specimens of the Quagga have dark stripes on the head and neck, but further back the stripes become paler and the interspaces darker, until they merge into a plain brownish color. It is also interesting to note that zebra stripes are like human fingerprints -- no two zebras have the same stripe pattern, which makes it easy to identify individuals. (Planet Wildlife, 1993)
Range mass: 250 to 300 kg.
Habitat and Ecology
Habitat and Ecology
In several areas, their movements are directly correlated with the availability of water, moving to grazing areas during the rains and concentrating near permanent rivers or pools during the dry season. The Serengeti migratory subpopulation concentrates during the rains from November to May in the Serengeti plains. At the beginning of the dry season in June it migrates to the western and northern parts of the Serengeti National Park and adjacent areas, and into the Mara National Reserve in Kenya (Klingel in press).
Quaggas were often found in arid to temperate grasslands, and sometimes wetter pastures.
Terrestrial Biomes: desert or dune ; savanna or grassland
The quagga was a successful grazer though they often competed with the more numerous wildebeest which frequently occurred in the same areas. Quaggas were often the first of the grazers to enter tall grass vegetation or possibly wet pastures. (Skeleton, 1992)
Life History and Behavior
Status: captivity: 40.0 years.
Status: wild: 20.0 years.
Quaggas were polygynous animals, meaning that there was mature male for each group,or "harem," of females. To become a harem stallion, a male had to abduct fillies in heat one at a time from their father's herds. Fillies began ovulating and advertising estrus by adopting a distinctive posture between one and two years of age. Many stallions gathered around a herd that included an estrus filly and fought for her with the herd stallion, and with each other. This occurred 5 days every month for about a year until the filly finally conceived. Though foals may be born in any month, there was a definite annual birth/mating peak early in December to January, which corresponds to the rain season in East Africa. Mares that were in good condition reproduced at 2-year intervals, having their first foal at 3 to 3.5 years. (Skeleton, 1992)
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1994Extinct(Groombridge 1994)
- 1990Extinct(IUCN 1990)
- 1988Extinct(IUCN Conservation Monitoring Centre 1988)
- 1986Extinct(IUCN Conservation Monitoring Centre 1986)
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2002Least Concern
- 1996Lower Risk/least concern
The last Quagga died in the Amsterdam Zoo in Holland on 12 August 1883. The last wild Quagga in South Africa was probably killed by hunters few years before that, perhaps in 1878. (S. Africas Threatened Wildlife, 1993) Though the South African Red Data Book refers to the Quagga as an extinct species, recent evidence has confirmed that it was actually a subspecies of the Burchell's Zebra. The South African Museum in Cape Town has now embarked on a project to selectively breed Burchell's Zebras with minimal striping on their hindquarters, until the same color pattern as the Quagga can be perhaps be re-created.
IUCN Red List of Threatened Species: extinct
The True Quagga subspecies (E. q. quagga) has been extinct since the end of the 19th century (ca. 1883).
Recorded densities of Plains Zebra include 0.9/km² in Kruger National Park (Smuts 1976) and 22/km² in Ngorongoro (ground count) (Klingel 1967).
The Quagga was driven to extinction in the late 19th century by overhunting and competition with livestock.
Hack et al. (2002) proposed the following conservation actions for the species: 1) Improve coverage and frequency of monitoring; 2) Improve risk assessment; 3) Quantify and manage genetic diversity both globally and locally; 4) Increase the understanding of the species' basic biology'; and 5) Investigare the economics of alternative utilization stategies.
Relevance to Humans and Ecosystems
Economic Importance for Humans: Positive
The Quagga was hunted to extinction by hunters and European settlers, who used their skins for grain bags, and prized them for their colors and patterns.
The quagga (//) (Equus quagga quagga) is an extinct subspecies of the plains zebra that lived in South Africa. It was long thought to be a distinct species, but recent genetic studies have shown it to be the southernmost subspecies of the plains zebra. It is considered particularly close to Burchell's zebra. Its name is derived from the plains zebra's call, which sounds like "kwa-ha-ha".
The quagga is believed to have been around 257 cm (8.43 ft) long and 125–135 cm (4.10–4.43 ft) tall at the shoulder. It was distinguished from other zebras by its limited pattern of primarily brown and white stripes, mainly on the front part of the body. The rear was brown and without stripes, and therefore more horse-like. The distribution of stripes varied considerably between individuals. Little is known about its behaviour but it may have gathered into herds of 30–50 individuals. Quaggas were said to be wild and lively, yet were also considered more docile than Burchell's zebra. They were once found in great numbers in the Karoo of the former Cape Province and the southern part of the former Orange Free State in South Africa.
Since Dutch settlement of South Africa began, the quagga was heavily hunted, and it competed with domesticated animals for forage. While some individuals were taken to zoos in Europe, breeding programs were not successful. The last wild population lived in the Orange Free State, and the quagga was extinct in the wild by 1878. The last captive specimen died in Amsterdam on 12 August 1883. Only one quagga was ever photographed alive and only 23 skins are preserved today. In 1984, the quagga was the first extinct animal to have its DNA analysed, and the Quagga Project is trying to recreate its pelage characteristics by selectively breeding Burchell's zebras.
The name "quagga" is derived from the Khoikhoi word for zebra and is onomatopoeic, being said to resemble the quagga's call, variously transcribed as "kwa-ha-ha" or "oug-ga". The name is still used colloquially for the plains zebra. The quagga was originally classified as a distinct species, Equus quagga, in 1778 by Dutch naturalist Pieter Boddaert. Today, the quagga and the other plains and mountain zebras are placed in the subgenus Hippotigris.
Historically, quagga taxonomy was further complicated by the fact that the extinct southernmost population of Burchell's zebra (Equus quagga burchellii) was thought to be a distinct subspecies (also sometimes thought a full species, E. burchellii). The extant northern population was later named Equus quagga antiquorum, which means that it is today also referred to as E. q. burchellii, after it was realised they were the same taxon. The extinct population was long thought very close to the quagga, since it also showed limited striping on its hind parts. As an example of this, Shortridge placed the two in the now disused subgenus Quagga in 1934. Most experts now suggest that the two subspecies represent two ends of a cline.
Some authors have described the quagga as a kind of wild horse rather than a zebra, and one craniometric study from 1980 seemed to confirm its affiliation with the horse (Equus caballus). There has been much debate over the status of the quagga in relation to the plains zebra. It is poorly represented in the fossil record, and the identification of these fossils is uncertain, as they were collected at a time when the name quagga referred to all zebras. Fossil skulls of Equus mauritanicus from Algeria have been claimed to show affinities with the quagga and the plains zebra, but they may be too badly damaged to allow definite conclusions to be drawn from them. Quaggas have also been identified in cave art attributed to the Bushmen.
Different subspecies of plains zebra were recognised as members of Equus quagga by early researchers, though there was much confusion over which species were valid. It has been pointed out that early morphological studies were erroneous, since using skeletons from stuffed specimens can be problematical, as early taxidermists sometimes used donkey and horse skulls inside their mounts when the originals were unavailable. Quagga subspecies were described on the basis of differences in striping patterns, but these differences were since attributed to individual variation within the same populations. Reginald Innes Pocock was perhaps the first to suggest that the quagga was a subspecies of plains zebra in 1902. As the quagga was scientifically described and named before the plains zebra, the trinomial name for the quagga becomes E. quagga quagga under this scheme, and the other subspecies of plains zebra are placed under E. quagga as well.
The quagga was the first extinct animal to have its DNA analysed, and this 1984 study launched the field of ancient DNA analysis. It confirmed that the quagga was more closely related to zebras than to horses, with the quagga and mountain zebra (Equus zebra) sharing an ancestor 3–4 million years ago. An immunological study published the following year found the quagga to be closest to the plains zebra. A 1987 study suggested that the mtDNA of the quagga diverged at a range of roughly 2% per million years, similar to other mammal species, and again confirmed the close relation to the plains zebra.
Later morphological studies came to conflicting conclusions. A 1999 analysis of cranial measurements found that the quagga was as different from the plains zebra as the latter is from the mountain zebra. A 2004 study of skins and skulls instead suggested that the quagga was not a distinct species, but a subspecies of the plains zebra. In spite of these findings, many authors subsequently kept the plains zebra and the quagga as separate species.
A genetic study published in 2005 confirmed the subspecific status of the quagga. It showed that the quagga had little genetic diversity, and that it diverged from the other plains zebra subspecies only between 120,000 and 290,000 years ago, during the Pleistocene, and possibly the penultimate glacial maximum. Its distinct coat pattern perhaps evolved rapidly because of geographical isolation and/or adaptation to a drier environment. In addition, plains zebra subspecies tend to have less striping the further south they live, and the quagga was the most southern-living of them all. Other large African ungulates diverged into separate species and subspecies during this period as well, probably because of the same climate shift.
The quagga is believed to have been 257 cm (8.43 ft) long and 125–135 cm (4.10–4.43 ft) tall at the shoulder. Its coat pattern was unique among equids: zebra-like in the front but more like a horse in the rear. It had brown stripes on the head and neck, brown upper parts and a white belly, tail and legs. The stripes were darkest on the head and neck and became gradually lighter further down the body, blending with the reddish brown of the back and flanks, until disappearing along the back. However it appears to have had a high degree of polymorphism, with some individuals having almost no stripes and others having patterns similar to the extinct southern population of Burchell's zebra, where the stripes covered most of the body except for the hind parts, legs and belly. It also had a broad dark dorsal stripe on its back. It had a standing mane with brown and white stripes.
The only quagga to have been photographed alive was a mare at the Zoological Society of London's Zoo. Five photographs of this specimen are known, and it died in 1872. On the basis of photographs and written descriptions, many observers suggest that the configuration of stripes on the quagga is light stripes on a dark background, contrary to the configuration in other zebras. Reinhold Rau, pioneer of the Quagga Project, claimed that this is an optical illusion: that the base colour is a creamy white and that the stripes are thick and dark. However, embryological evidence instead supports zebras being dark coloured with white as an addition.
Living in the very southern end of the plains zebra's range, the quagga had a thick winter coat that moulted each year. Its skull was described as having a straight profile and a concave distema, and as being relatively broad with a narrow occiput. Like other plains zebras, the quagga did not have a dewlap on its neck as the mountain zebra does. The 2004 morphological study found that the skeletal features of the southern Burchell's zebra population and the quagga overlapped, and that they were impossible to distinguish. Some specimens also appeared to be intermediate between the two in striping, and individuals of the extant Burchell's zebra population still exhibit limited striping. It can therefore be concluded that the two subspecies graded morphologically into each other. Today, some stuffed specimens of quaggas and southern Burchell's zebra are so similar that they are impossible to definitely identify as either, since no location data was recorded. The female specimens used in the study were larger than the males on average.
Behaviour and ecology
The quagga was the southernmost distributed plains zebra, mainly living south of the Orange River. It was a grazer, and its habitat range was restricted to the grasslands and arid interior scrubland of the Karoo region of South Africa, today forming parts of the provinces of Northern Cape, Eastern Cape, Western Cape and the Free State. These areas were known for distinctive flora and fauna and high amounts of endemism.
Little is known about the behaviour of quaggas in the wild, and it is sometimes unclear what exact species of zebra is referred to in old reports. The only source that unequivocally describes the quagga in the Free State is that of the English military engineer and hunter Major Sir William Cornwallis Harris. His 1840 account reads as follows:
The geographical range of the quagga does not appear to extend to the northward of the river Vaal. The animal was formerly extremely common within the colony; but, vanishing before the strides of civilisation, is now to be found in very limited numbers and on the borders only. Beyond, on those sultry plains which are completely taken possession of by wild beasts, and may with strict propriety be termed the domains of savage nature, it occurs in interminable herds; and, although never intermixing with its more elegant congeners, it is almost invariably to be found ranging with the white-tailed gnu and with the ostrich, for the society of which bird especially it evinces the most singular predilection. Moving slowly across the profile of the ocean-like horizon, uttering a shrill, barking neigh, of which its name forms a correct imitation, long files of quaggas continually remind the early traveller of a rival caravan on its march. Bands of many hundreds are thus frequently seen doing their migration from the dreary and desolate plains of some portion of the interior, which has formed their secluded abode, seeking for those more luxuriant pastures where, during the summer months, various herbs thrust forth their leaves and flowers to form a green carpet, spangled with hues the most brilliant and diversified.
Quaggas have been reported gathering into herds of 30–50 individuals and sometimes travelled in a linear fashion. They may have been sympatric with Burchell's zebra between the Vaal and Orange rivers. However, this is disputed, and there is no evidence that they interbred. It could also have shared a small portion of its range with Hartmann's mountain zebra (Equus zebra hartmannae).
Since the practical function of striping has not been determined for zebras in general, it is unclear why the quagga lacked stripes on its hind parts. A cryptic function for protection from predators (stripes obscure the individual zebra in a herd) and tsetse flies (these flies are less attracted to striped objects), as well as various social functions, have been proposed for zebras in general. Differences in hind quarter stripes may have aided species recognition during stampedes of mixed herds, so that members of one subspecies or species would follow its own kind. It has also been hypothesised that the zebras developed striping patterns as thermoregulation to cool themselves down, and that the quagga lost them due to living in a cooler climate, although one problem with this is that the mountain zebra lives in similar environments and has a bold striping pattern.
Quaggas were said to be lively and highly strung, especially the stallions. During the 1830s, quaggas were used as harness animals for carriages in London, the males probably being gelded to mitigate their volatile nature. Local farmers used them as guards for their livestock, as they were likely to attack intruders. On the other hand, captive quaggas in European zoos were said to be tamer and more docile than Burchell's zebra. One specimen was reported to have lived in captivity for 21 years and 4 months, dying in 1872.
Decline and extinction
As they were easy to find and kill, the quagga was hunted by early Dutch settlers and later by Afrikaners to provide meat or for their skins. The skins were traded or used locally. The quagga was probably vulnerable to extinction due to its limited distribution, and it may have competed with domestic livestock for forage. The quagga had disappeared from much of its range by the 1850s. The last population in the wild, located in the Orange Free State, was extirpated in the late 1870s. The last known wild individual died in 1878.
Individual quaggas were also captured and shipped to Europe, where they were displayed in zoos. Lord Morton tried to save the animal from extinction by starting a captive breeding program. However, he was only able to obtain a single male which, in desperation, he bred with a female horse. This produced a female hybrid which bore the zebra stripes on its back and legs. Lord Morton's mare was sold and was subsequently bred with a black stallion, resulting in offspring that again had zebra stripes. An account of this was published in 1820 by the Royal Society. This lead to new ideas on telegony, referred to as pan-genesis by Charles Darwin.
The last captive specimen, a female in Amsterdam's Natura Artis Magistra zoo, had lived there from 9 May 1867 until it died on 12 August 1883, but its origin and cause of death were not recorded. The specimen in London died in 1872 and the one in Berlin in 1875. There are 23 known stuffed and mounted quagga specimens throughout the world. In addition, there is a mounted head and neck, a foot, seven complete skeletons, and samples of various tissues. A twenty-fourth mounted specimen was destroyed in Königsberg, Germany, during World War II.
Breeding back project
After the very close relationship between the quagga and surviving zebras was discovered, the Quagga Project was started in 1986 by Reinhold Rau in South Africa to recreate the quagga by selective breeding from plains zebra stock, with the eventual aim of reintroducing them to the wild. The founding population consisted of 19 individuals from Namibia and South Africa, chosen because they had reduced striping on the rear body and legs. The first foal of the project was born in 1988. Once a sufficiently quagga-like population has been created, it will be released in the Western Cape. In early 2006, the third and fourth generation animals produced by the project were reported to look very much like the depictions and preserved specimens of the quagga. This type of selective breeding is called breeding back. The practice is controversial, since the resulting zebras will resemble the quaggas only in external appearance, while genetically they will be different. The technology to use recovered DNA for cloning does not exist.
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|This article's lead section may not adequately summarize key points of its contents. (April 2013)|
The plains zebra (Equus quagga, formerly Equus burchelli), also known as the common zebra or Burchell's zebra, is the most common and geographically widespread species of zebra. It ranges from the south of Ethiopia through East Africa to as far south as Botswana and eastern South Africa. The plains zebra remains common in game reserves, but is threatened by human activities such as hunting for its meat and hide, as well as competition with livestock and encroachment by farming on much of its habitat.
- 1 Taxonomy
- 2 Physical description
- 3 Ecology
- 4 Behavior
- 5 Human interactions
- 6 References
- 7 Bibliography
- 8 External links
There is a dispute among biologists as to how to properly classify the various species of Zebra. It is thought that the plains zebra and mountain zebra belong to the subgenus Hippotigris and that Grévy's zebra is the sole species of subgenus Dolichohippus. This is on account of Grévy's zebra resembling an ass (subgenus Asinus), while the plains zebra and mountain zebra are more horse-like. All three animals belong to the genus Equus along with other living equids. However, recent phylogenetic evidence suggests that the mountain zebras and Grévy's zebras to be classified with asses and donkeys in a lineage separate from the Plains zebra. In areas where Plains zebras are sympatric with Grévy's zebras, it is not unusual to find them in the same herds and fertile hybrids occur. In captivity, Plains zebras have been crossed with mountain zebras. The hybrid foals lacked a dewlap and resembled the plains zebra apart from their larger ears and their hindquarters pattern.
In 2004, C. P. Groves and C. H. Bell investigated the taxonomy of the zebra genus, Equus, subgenus Hippotigris. They published their research in the journal Mammalian Biology. They revised the subspecies of the plains zebra Equus quagga. Six subspecies are now recognizable.
- Quagga, †Equus quagga quagga – Boddaert, 1785
- Burchell's zebra, Equus quagga burchellii – Gray, 1824
- Grant's zebra, Equus quagga boehmi – Matschie, 1892
- Maneless zebra Equus quagga borensis – Lönnberg, 1921
- Chapman's zebra, Equus quagga chapmani – Layard, 1865
- Crawshay's zebra, Equus quagga crawshayi – De Winton, 1896
Sometimes another subspecies is distinguished in Eastern Zimbabwe and Western Mozambique:
- Selous' zebra, Equus quagga selousi - Pocock 1897
The quagga was originally classified as a separate species, Equus quagga, in 1778. Over the next 50 years or so, many other zebras were described by naturalists and explorers. Because of the great variation in coat patterns (no two zebras are alike), taxonomists were left with a great number of described "species", and no easy way to tell which of these were true species, which were subspecies, and which were simply natural variants. The quagga was the first extinct creature to have its DNA studied. Recent genetic research at the Smithsonian Institution has demonstrated that the quagga was in fact not a separate species at all, but diverged from the plains zebra, between 120,000 and 290,000 years ago, and suggests that it should be named Equus burchelli quagga. However, according to the rules of biological nomenclature, where there are two or more alternative names for a single species, the name first used takes priority. As the quagga was described about thirty years earlier than the Burchell's zebra, it appears that the correct terms are E. quagga quagga for the quagga and E. quagga burchelli for the plains zebra, unless "Equus burchelli" is officially declared to be a nomen conservandum.
Burchell's zebra was thought to have been hunted to extinction. However Groves and Bell concluded in their 2004 publication that "the extinct true Burchell's zebra" is a phantom. Careful study of the original zebra populations in Zululand and Swaziland, and of skins harvested on game farms in Zululand and Natal, has revealed that a certain small proportion shows similarity to what now is regarded as typical "burchellii". The type localities of the subspecies Equus quagga burchellii and Equus quagga antiquorum (the Damara zebra) are so close to each other that the two are in fact one, and that therefore the older of the two names should take precedence over the younger. They therefore say that the correct name for the southernmost subspecies must be burchellii not antiquorum. The subspecies Equus quagga burchellii still exists in KwaZulu-Natal and in Etosha.
The plains zebra is mid-sized, smaller on average than the other two zebra species, and thick bodied with relatively short legs. There is some variation in size, based on the animals' condition and subspecies. Adults of both sexes can stand from 1.1 to 1.47 m (3.6 to 4.8 ft) high at the withers (shoulder), are 2 to 2.5 m (6.6 to 8.2 ft) long, not counting a 50 cm (20 in) tail, and weigh 175 to 387 kg (386 to 853 lb). About 14.2hh to 16.0 hh. Males may weigh 10% more than females.
Like all zebras, they are boldly striped in black and white, and no two individuals look exactly alike. They also have black or dark muzzles. The natal coat of a foal is brown and white. All have vertical stripes on the forepart of the body, which tend towards the horizontal on the hindquarters. The northern populations have narrower and more defined striping; southern populations have varied but lesser amounts of striping on the underparts, the legs and the hindquarters. Southern populations also have brown "shadow" stripes between the black and white coloring. These are absent or poorly expressed in northern zebras.
Embroyoloical evidence has shown that the zebra's background color is dark and the white is an addition. The first subspecies to be described, the now-extinct quagga, had plain brown hindquarters. There have been various mutations of the zebra's pelage from mostly white to mostly black. Rare albino zebras have been recorded in the forests of Mount Kenya.
Function of the stripes
The striping pattern of the zebra is unique among sympatric ungulates. One suggested function for the stripes is to camouflage the animal in tall grass or in the dappled shade beneath bushes and trees. However, animals that use camouflage, like the kudu and bushbuck, tend to be quiet and stealthy. They freeze when there is danger and flee only at the last moment. By contrast, the zebra is active and noisy, and makes no attempt to hide itself. Another suggestion is that the stripes affect a predator's judgement of the zebra's size, distance and what direction it is going in. However, zebra stripes do not appear to affect any of these. A related hypothesis is that the stripes make it difficult for a predator to single out and learn about on an individual during a chase. Perhaps the best explanation for the stripes is that they serve a social function. Individual zebras can apparently recognize each other by their striping patterns. The stripes may also serve as visual cues for grooming. In addition, they could serve to help zebra groups stay together when they are fleeing. Recent studies suggest that stripes may have developed to discourage biting flies. Experiments have demonstrated that the stripes polarize light in such a way that it discourages tabanids (biting flies) in a manner not shown with other coat patterns.
Range and habitat
The Plains zebra's range stops short of the Sahara from South Sudan and southern Ethiopia extending south along eastern Africa, as far as Zambia, Mozambique, and Malawi, before spreading into most southern African countries. They are regionally extinct in Burundi and Lesotho, and they may have lived in Algeria in the Neolithic Era.
Plains zebras generally live in treeless grasslands and savanna woodlands but can be found in a variety of habitats, both tropical and temperate. However they are generally absent from deserts, dense rainforests and permanent wetlands. Zebras also live in elevations from sea level to 4,300 m on Mount Kenya. They rely on rainfall for food and water, and go on great migrations to follow the rains. The zebras will migrate up to 700 miles (1,100 km) for food. Other grazers also migrate. Plains zebras are highly water-dependent and are usually found within 25–30 kilometers of a water source.
Diet and predation
In one study, the zebra's diet was estimated to be 92% grass, 5% herbs, and 2% shrubs. Unlike many of the large ungulates of Africa, the plains zebra does not require (but still prefers) short grass to graze. It eats a wide range of different grasses, preferring young, fresh growth where available, and also browses on leaves and shoots from time to time. In consequence, it ranges more widely than many other species, even into woodlands, and it is often the first grazing species to appear in a well-vegetated area. Zebras have a simple stomach and use hindgut fermentation (caeco-colic) which allows them to digest and assimilate larger amounts of forage during a 24-hour period. Thus, zebras are less selective in foraging, but they do spend much time eating. The zebra is a pioneer grazer and prepares the way for more specialized grazers like blue wildebeests and Thomson's gazelles who depend on shorter and more nutritional grasses.
The plains zebra's major predators are lions and spotted hyenas. Nile crocodiles are also great threats during migratory river crossings. Wild dogs, cheetahs, and leopards also prey on zebras, although the threats they pose are generally minor and they mostly attack the foals. Olive Baboons may prey on foals, but pose no threat to adults. The zebra can be a formidable adversary, since they have a strong bite and a kick powerful enough to kill land predators. They often try to outrun larger predators such as lions and spotted hyenas, whereas they often stand their ground with the smaller predators.
Interactions with other grazers
Plains zebra herds will mix and migrate together along with other species such as wildebeests. Wildebeests and zebras generally coexist peacefully and will alert each other to predators. However, aggressive interactions occasionally occur.
The plains zebra is highly social and usually forms small family groups called harems, which consist of a single stallion, several mares, and their recent offspring. The adult membership of a harem is highly stable, typically remaining together for months to years. Groups of all male "bachelors" also exist. These are stable groups of 2-15 males with an age-based hierarchy lead by a young male. These males stay in their groups until they are ready to start a harem. The bachelors prepare for their adult roles with play fights and greeting/challenge rituals, which take up most of their activities. Multiple harems and bachelor groups come together to form herds. Plains zebras are unusual among harem-holding species in forming these groups. In addition, pairs of harems may create temporarily stable subgroups within a herd, allowing individuals to interact with those outside their group. Among harem-holding species, this has only been observed in primates like the gelada and the hamadryas baboon.
Stallions form harems by abducting young mares from their family harems. When a mare reaches sexual maturity, she will exhibit the estrous posture, which attracts nearby stallions, both bachelors and harem leaders. Her harem stallion (usually her father) will chase off or fight stallions attempting to abduct her. Even after a young mare is isolated from her natal harem, the fight over her continues until her estrous cycle is over, and it starts again with the next estrous cycle. It is rare that the mare's original abductor keeps her for long. When the mare finally ovulates, the male that impregnates her keeps her for good. Thus, the mare becomes a permanent member of a new harem.
Mares exist in a hierarchy, with the alpha female being the first to mate with the stallion and being the one to lead the group. When new mares are added to the group, they are met with hostility by the other mares. Thus, the stallion must shield the new mares until the aggression subsides. The most recently added females rank lowest. Females that become unfit or weak may drop in their rank, though. The female memberships of a harem stay intact even if a new stallion takes over. Females in a harem tend to be hostile to outside females. Zebras strengthen their social bonds with grooming. Members of a harem nip and scrape along the neck, shoulders, and back with their teeth and lips. Mothers and foals groom the most often, followed by siblings. Grooming shows social status and eases aggressive behavior.
A stallion will defend his group from other males. When challenged, the stallion would issue a warning to the invader by rubbing nose or shoulder with him. If the warning is not heeded, a fight breaks out. Zebra fights often become very violent, with the animals biting at each other's necks, heads or legs, wrestling to the ground, and occasional kicking. Sometimes a stallion will lie still on the ground as if surrendering, but once the other male lets up, will strike and continue the fight. Most fighting occurs over young mares in estrus, and as long as a harem stallion is healthy, he will usually not be challenged. Only unhealthy stallions have their harems taken over, and even then the new stallion gradually takes over pushing the old one out without a fight.
At least six different calls have been documented for the plains zebra. One of which is its distinctive high-pitched contact call heard as "a-ha, a-ha, a-ha" or "kwa-ha, kaw-ha, ha, ha". When a predator is sighted, a zebra will make a two-syllable alarm call. A loud snort is made when moving in cover of potential danger. When in contentment, a zebra will make a more drawn-out snort. Males will make a short high-pitched squeal when hurt and foals will emit a drawn out wail when in distress. There are two main facial expressions made by zebras. One is for greeting and involves the ears sticking up and directed forward; the other is threatening and involves the ears down.
The stallion mates with all his mares. Mares may give birth to one foal every twelve months. The birthing peak is during the rainy season. She nurses the foal for up to a year. The stallion is generally intolerant of foals that are not his. It is possible that zebras practice infanticide and feticide, although such incidences have only been observed in captive individuals. Like horses, zebras are able to stand, walk, run from danger, and suckle shortly after they are born. At the moment of birth, a mother zebra keeps any other zebra away from her foal, including the stallion, the other mares, and even the previous offspring. Later, though, they all bond. Within the group, a foal has the same rank as its mother. Plains zebra foals are protected by their mother as well as the head stallion and the other mares in their group. Even with parental protection, up to 50% of zebra foals are taken by predation, disease, and starvation each year.
Young male zebras eventually leave their family groups. This is not because of sexual maturity or being kicked out by their fathers, but because their relationship with their mothers have faded after the birth of a sibling. The young stallion then seeks out other young stallions for company. Young females may stay in the harem until they are abducted by another stallion.
For protection from land predators, the plains zebra retreats into open areas with good visibility at night. When the groups forage or sleep, one zebra will keep watch, and if a predator is spotted, it will bark or snort loudly. When being hunted by hyenas or wild dogs, a zebra harem stays close together and cooperates to protect threatened members, particularly the young. The harem stallion will go on the offensive and attack the dogs or hyenas. Though hyenas may harass the stallion, they usually only concentrate on the herd, and attempt to dodge the stallion's assaults. Unlike stallions, mares typically only react aggressively to hyenas or dogs when their foals are threatened. Unlike wildebeest, zebras rarely take to water when escaping hyenas. With lions, a zebra's best defense is to outpace them, as lions do not have as much endurance as hyenas or wild dogs. Cheetahs and leopards are mostly threats to foals as an adult zebra is fully capable of driving them away.
Overall, the plains zebra population remains stable, and the species faces no major threat that would cause range-wide decline. The zebra can be found in numerous protected areas across its range, including the Serengeti National Park in Tanzania, Tsavo and Masai Mara in Kenya, Hwange National Park in Zimbabwe, Etosha National Park in Namibia, and Kruger National Park in South Africa. There are some stable populations in unprotected areas.
Some local populations, though, have faced great declines and even extinctions. One subspecies, the quagga, is now extinct. In Tanzania, the zebra population has decreased by 20% from the late 1990s to the mid-2000s. Zebras are threatened by hunting for their hide and meat, and habitat change from farming. They also compete with livestock for food, and are sometimes culled. Poaching is largely a threat to northern populations, while southern populations are threatened mostly by habitat loss. Recent civil wars in Rwanda, Somalia, South Sudan, Ethiopia, and Uganda have caused dramatic declines in all wildlife populations, including those of plains zebra. It is now extinct in Burundi. Civil war in Angola during much of the past 25 years has devastated its wildlife populations, including its once-abundant plains zebra, and destroyed the national parks administration and infrastructure.
Nevertheless, plains zebras are protected in most of their range. They are an important economic source in tourism.
The zebra is revered in some African cultures as a symbol of beauty. In the dances of the Karamojong tribe of Uganda, women would paint themselves in zebra stripes and act like them. The Dube tribe of South Africa features a zebra on its totem. Zebras also appear on the coat of arms of Botswana.
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