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and asses, zebras have never been truly domesticated.
There are three species of zebras: the plains zebra, the grevy’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 them one of 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, became extinct in the late 19th century — though there is currently a plan, called the Quagga Project, that aims to breed zebras that are phenotypically similar to the quagga in a process called breeding back.
Zebras evolved among the Old World horses within the last four million years. Grevy’s zebras (and perhaps also mountain zebras) are, together with asses and donkeys, in a separate lineage from 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.
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 colour is black and the white stripes and bellies are additions.
It is likely that the stripes are caused by a combination of factors.
A mother nursing her young blends into a stand of deadwood.
The 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.
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 colour 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.
3. It has been suggested that the stripes serve as visual cues and identification.
Although the striping pattern is unique to each individual, it is not known whether zebras can recognise 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
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. — Wikipidea.