There are three species of zebras: the plains zebra, the Grévy’s zebra and the mountain zebra. The plains zebra and the mountain zebra belong to the subgenus Hippotigris, but Grevy’s zebra is the sole species of subgenus Dolichohippus. The latter resembles an ass, to which it is closely related, while the former two are more horse-like. All three belong to the genus Equus, along with other living equids. The unique stripes of zebras make these among the animals most familiar to people. They occur in a variety of habitats, such as grasslands, savannas, woodlands, thorny scrublands, mountains, and coastal hills. However, various anthropogenic factors have had a severe impact on zebra populations, in particular hunting for skins and habitat destruction. Grevy’s zebra and the mountain zebra are endangered. While plains zebras are much more plentiful, one subspecies, the quagga, went extinct in the late 19th century, though they have now been rebred from zebra DNA.Zebras evolved among the Old World horses within the last 4 million years. Grevy’s zebras (and perhaps also Mountain Zebras) are with asses and donkeys in a separate lineage from the other zebra lineages. This means either that striped equids evolved more than once, or that common ancestors of zebras and asses were striped and only zebras retained the stripes. Extensive stripes are posited to have been of little use to equids that live in low densities in deserts (like asses and some horses) or ones that live in colder climates with shaggy coats and annual shading (like some horses). Fossils of an ancient equid were discovered in the Hagerman Fossil Beds National Monument in Hagerman, Idaho. It was named the Hagerman horse with a scientific name of Equus simplicidens. It is believed to have been similar to the Grevy’s zebra. The animals had stocky zebra-like bodies and short, narrow, donkey-like skulls. Grevy’s zebra also has a donkey-like skull. The Hagerman horse is also called the American zebra or Hagerman zebra.Size and weight The common plains zebra is about 50-52 inches (12.2-13 hands, 1.3 m) at the shoulder with a body ranging from 6-8.5 feet (2-2.6 m) long with an 18-inch (0.5 m) tail. It can weigh up to 770 pounds (350 kg), males being slightly bigger than females. Grévy’s Zebra is considerably larger, while the mountain zebra is somewhat smaller. Stripes It was previously believed that zebras were white animals with black stripes, since some zebras have white underbellies. Embryological evidence, however, shows that the animal’s background color is black and the white stripes and bellies are additions. It is likely that the stripes are caused by a combination of factors.stripes are typically vertical on the head, neck, forequarters, and main body, with horizontal stripes at the rear and on the legs of the animal. The “zebra crossing” is named after the zebra’s black and white stripes. A wide variety of hypotheses have been proposed to account for the evolution of the striking stripes of zebras. The more traditional of these (1 & 2, below) relate to camouflage. 1. The vertical striping may help the zebra hide in grass. While seeming absurd at first glance, considering that grass is neither white nor black, it is supposed to be effective against the zebra’s main predator, the lion, which is color blind[dubious – discuss]. In addition, even at moderate distances, the striking striping merges to an apparent grey. 2. Another hypothesis is that since zebras are herd animals, the stripes may help to confuse predators–a number of zebras standing or moving close together may appear as one large animal, making it more difficult for the lion to pick out any single zebra to attack.[unreliable source?] 3. It has been suggested that the stripes serve as visual cues and identification. Although each striping pattern is unique to each individual, it is not known whether zebras can recognize one another by their stripes. 4. At least two experiments indicate that the disruptive colouration is an effective means of confusing the visual system of flies, in one case the blood-sucking tsetse fly, in another horseflies (tabanids). 5. Alternative theories include that the stripes coincide with fat patterning beneath the skin, serving as a thermo-regulatory mechanism for the zebra, or that wounds sustained disrupt the striping pattern to clearly indicate the fitness of the animal to potential mates. A zebra walking Gaits Like horses, zebras walk, trot, canter and gallop. They are generally slower than horses, but their great stamina helps them outpace predators. When chased, a zebra will zig-zag from side to side, making it more difficult for the predator. When cornered, the zebra will rear up and kick or bite its attacker.