The plains zebra (Equus quagga, formerly Equus burchellii) is the most common and geographically widespread species of zebra. Its range is fragmented, but spans much of southern and eastern Africa south of the Sahara. Six or seven subspecies have been recognised, including the quagga which was thought to be a separate species. More recent research supports variations in zebra populations being clines rather than subspecies.
Plains zebras are intermediate in size between the larger Grévy's zebra and the smaller mountain zebra and tend to have broader stripes than both. Great variation in coat patterns exists between clines and individuals. The plains zebra's habitat is generally, but not exclusively, treeless grasslands and savanna woodlands, both tropical and temperate. They generally avoid desert, dense rainforest and permanent wetlands. Zebras are preyed upon by lions and spotted hyenas, Nile crocodiles and, to a lesser extent, leopards, cheetahs and African wild dogs.
Plains zebras are a highly social species, forming harems with a single stallion, several mares and their recent offspring; bachelor groups also form. Groups may come together to form herds. The animals keep watch for predators; they bark or snort when they see a predator and the harem stallion attacks predators to defend his harem.
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. The loss of open grasslands due to woody plant encroachment increases predation risk and therewith habitat. Plains zebra are listed as near threatened by the IUCN as of 2016. The species population is stable and not endangered, though populations in most countries have declined sharply.
Taxonomy The plains zebra was formally classified by British zoologist John Edward Gray in 1824 as Equus burchellii. After the quagga, described by Pieter Boddaert in 1785, was found to be the same species in the 21st century, the plains zebra was reclassified as Equus quagga due to the principle of priority. The plains zebra and mountain zebra were traditionally placed in the subgenus Hippotigris, in contrast to Grévy's zebra, which was considered the sole species of the subgenus Dolichohippus; however, recent (2013) phylogenetic evidence finds that plains zebras are more closely related to Grévy's zebras than mountain zebras. Groves and Bell (2004) place all three species in the subgenus Hippotigris, and zebras appear to be a monophyletic lineage. In areas where plains zebras are sympatric with Grévy's zebras, finding them in the same herds is not unusual, and fertile hybrids occur.
Subspecies In their 2004 study of cranial and pelage differences between specimens, Groves and Bell found support for the division of the plains zebra into six subspecies: Image Subspecies DistributionManeless zebra, Equus quagga borensis – Lönnberg, 1921 Northwestern Kenya (from Uasin Gishu and Lake Baringo) to the Karamoja district of Uganda.Grant's zebra, Equus quagga boehmi – Matschie, 1892 Zambia west of the Luangwa River and west to Kariba, Katanga Province of the Democratic Republic of the Congo, north to the Kibanzao Plateau, and in Tanzania north from Nyangaui and Kibwezi into southwestern Kenya as far as Sotik and southwestern Ethiopia from Omo Valley to Nechisar plains in the north and Yabello and Borena Zone to the east. Crawshay's zebra, Equus quagga crawshayi – De Winton, 1896 Eastern Zambia, east of the Luangwa River, Malawi, southeastern Tanzania, and northern Mozambique south to the Gorongoza District Chapman's zebra, Equus quagga chapmani – Layard, 1865 North-east South Africa, north to Zimbabwe, west into Botswana, the Caprivi Strip in Namibia, and southern Angola. Burchell's zebra, Equus quagga burchellii – Gray, 1824 Southern Botswana to Etosha and the Kaokoveld, and southeast to Eswatini and KwaZulu-Natal. Quagga, †Equus quagga quagga – Boddaert, 1785 South Africa Selous' zebra, Equus quagga selousi – Pocock, 1897* Mozambique *Sometimes a seventh subspecies is recognised.
Burchell's zebra was thought to have been hunted to extinction. However, Groves and Bell concluded that "the extinct true Burchell's zebra is a phantom". Careful study of the original zebra populations in Zululand and Eswatini 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 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 suggested that the correct name for the subspecies must be burchellii, not antiquorum.
A 2005 genetic study confirmed the quagga being the same species as the plains zebra. It showed that the quagga had little genetic diversity and that it diverged from the other plains zebra subspecies only 120,000–290,000 years ago, during the Pleistocene and, possibly, the penultimate glacial maximum. Its distinct coat pattern may have 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.
The simplified cladogram below is based on the 2005 analysis (some taxa shared haplotypes and could therefore not be differentiated):
A 2018 DNA study found no evidence for a subspecies structure in plains zebras but, instead, observed a north–south genetic continuum. Modern plains zebra populations appear to have originated from Southern Africa around 370,000 years ago with plains zebras in Uganda, the most northern population, being the most distinct.
Physical description
The plains zebra stands at a height of with a head-body length of and a tail length of . Males weigh while females weigh . The species is intermediate in size between the larger Grévy's zebra and the smaller mountain zebra. It is stocky with relatively short legs and a skull with a convex forehead and a somewhat concave nose profile. The neck is thicker in males than in females. The ears are upright and have rounded tips. They are shorter than in the mountain zebra and narrower than in Grévy's zebra. As with all wild equids, the plains zebra has an erect mane along the neck and a tuft of hair at the end of the tail. The body hair of a zebra is , shorter than in other African ungulates.
Like all zebras, they are boldly striped in black and white and no two individuals look exactly alike. Compared to other species, the plains zebra has broader stripes. The stripes are vertical on the fore part of the body, and tend towards the horizontal on the hindquarters. Northern zebra populations have narrower and more defined striping; southern populations have varied but lesser amounts of striping on the under parts, the legs and the hindquarters. Southern populations also have brown "shadow" stripes between the black and white colouring. These are absent or poorly expressed in northern zebras. The natal coat of a foal is brown and white and the brown darkens with age.
Various abnormalities of the patterns have been documented in plains zebras. Melanistic zebras have high concentrations of dark stripes on the torso but low concentrations on the legs. "Spotted" individuals display interruptions in black striping patterns. There have even been morphs with white spots on dark backgrounds. Striping abnormalities have been linked to inbreeding. Albino zebras have been recorded in the forests of Mount Kenya, with the dark stripes being blonde. The quagga had brown and white stripes on the head and neck, brown upper parts and a white belly, tail and legs.
Ecology
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 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. They generally prefer Acacieae woodlands over Commiphora. They are water-dependent and live in more mesic environments than other African equids. They seldom wander from a water source. Zebras also live in elevations from sea level to on Mount Kenya.
Depending on the population, zebra herds may be sedentary, being highly dense with small ranges, or migratory, being less populated with separate, extensive dry and wet home ranges. When migrating, zebras appear to rely on some memory of the locations where foraging conditions were best and may predict conditions months before their arrival.
The loss of open grasslands due to woody plant encroachment increases predation risk and therewith habitat.
Diet and predation Plains zebras primarily feed on grass; preferred species being Themeda triandra, Cynodon dactylon, Eragrostis superba and Cenchrus ciliaris. Zebra sometimes browse on herbs, leaves and twigs or dig for corms and rhizomes during the dry season. They appear to partial to eating scorched Colophospermum mopane and Pterocarpus rotundifolius, consuming both the leaves and twigs.
Plains zebras are adapted for grazing on both long, tough grass stems and newly emerging short grass (stems and sheaths). In some areas, it rarely feeds below to ground level. 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. The flexible upper lip allows them to push plant material between the incisors to cut. Zebras have a less efficient digestive system than ruminants but food passage is twice as fast. 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 specialised grazers such as blue wildebeests and Thomson's gazelles.
The plains zebra's major predators are lions and spotted hyenas. Lions are most successful when targeting lone individuals, usually an old male while hyenas chase and isolate an individual from the group, usually a female or foal. Nile crocodiles also prey on zebras when they are near water. Less common predators include leopards, cheetahs and African wild dogs, which mostly hunt foals. When in the presence of a lion, zebras remain alert and stand in a semi-circle at as much as and no less than . Stallions sometimes try to drive lions away with bluff charges. By contrast, zebras may approach cheetahs and wild dogs and a single hyena is allowed to come within a few metres. To escape from predators, an adult zebra can run at . 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 goes on the offensive and attacks the dogs or hyenas.
Behaviour Plains zebras are nomadic and non-territorial, home ranges vary from to , depending on the area and if the population is migratory. They are more active during the day and spend most of their time feeding. Other activities include dust bathing, rubbing, drinking and intermittent resting which is very brief. At night, zebra activity is subdued except when threatened by predators. They may rest or sleep laying down, while one individual keeps guard.
Social structure