The plains zebra (Equus quagga, formerly Equus burchellii), also known as the common zebra, 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 subspecies have been recognised including the extinct quagga which was thought to be a separate species. However, more recent research supports variations in zebra populations being clines rather than subspecies.
The plains zebra is intermediate in size between the larger Grévy's zebra and the smaller mountain zebra; and tends to have broader stripes than both. Great variation in coat patterns exists between clines and individuals. The plain 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 and to a lesser extent crocodiles, cheetahs, and African wild dogs. The plains zebra is 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 species population is stable and not endangered, though populations in most countries have declined sharply. As of 2016, the plains zebra is classified as near threatened by IUCN.
Description & appearance
The plains zebra stands at a height of 127–140 cm (4.17–4.59 ft) with a head-body length of 217–246 cm (7.12–8.07 ft) and a tail length of 47–56.5 cm (1.54–1.85 ft). Males weigh 220–322 kg (485–710 lb) while females weigh 175–250 kg (386–551 lb). The species is intermediate in size between the larger Grévy's zebra and the smaller mountain zebra. It is dumpy bodied 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 the 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 9.4 ± 4 mm (0.37 ± 0.16 in), 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.
Embryological evidence has shown that the zebra's background colour is dark and the white is an addition. The first subspecies to be described, the now-extinct quagga, had plain brown hindquarters. Various mutations of the zebra's pelage have occurred, from mostly white to mostly black. Rare albino zebras have been recorded in the forests of Mount Kenya.
The purpose of the bold black-and-white striping of zebras has been a subject of debate among biologists for over a century. A 2012 study suggests 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. A 2014 study also supports the theory that they are a form of protection from biting flies and compared to other wild equines, zebras live in areas with the highest fly activity. The quagga appears to have lived in areas with lesser amounts of fly activity than other zebras. Another study from 2015 determined that environment temperature is a strong predictor for zebra striping patterns and proposed that the stripes may be related to thermoregulation.
Distribution & 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 10–12 km (6.2–7.5 mi) from a water source. Zebras also live in elevations from sea level to 4,300 ft 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 were foraging conditions were best and may predict conditions months after their arrival. Food
Plains zebras primarily feed on grass; preferred species being Themeda triandra, Cynodon dactylon, Eragrostis superba and Cenchrus ciliaris. Zebra sometimes browse 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. In some areas, it rarely feeds below 100–150 mm (3.9–5.9 in) 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. Reproduction
The stallion mates with all his mares. Males exhibit the flehmen response to test for female respectability which involves the upper lip curling back to smell for urine (via the vomeronasal organ). The female signals her readiness for copulation by straddling her legs and raising her tail. The gestation period lasts around a year, and a single young is produced. Mares may give birth to one foal every 12 months. The birthing peak is during the rainy season. A mare gives birth within the vicinity of her group and while laying down on her side. The newborn foal weighs 30–35 kg (66–77 lb) and the afterbirth is rarely consumed. A newborn is capable of standing almost immediately and starts to eat grass within a week. 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. The stallion is generally intolerant of foals that are not his and zebras may practice infanticide and feticide.
Mortality for foals is high in their first year of life and is usually caused by predation. However, zebra young are afforded more protection then those of species like wildebeest and hartebeest. A foal is usually weaned at around 11 months, but may suckle for longer. Females reaches puberty at 2.5 years while males do so at 5–6 years. Young male zebras eventually leave their family groups as the relationships with their mothers has 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.