Zebras, Zebra Pictures, Zebra Facts - National Geographic

Zebras evolved among the Old World horses within the last 4 million years. Grévy'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 inHagerman, Idaho. It was named the Hagerman horse with a scientific name of Equus simplicidens. It is believed to have been similar to the Grévy's zebra.The animals had stocky zebra-like bodies and short, narrow, donkey-like skulls. Grévy's zebra also has a donkeylike skull. The Hagerman horse is also called the American zebra or Hagerman zebra.

                 

                         

Classification

The plains zebra (Equus quagga, formerly Equus burchelli) is the most common, and has or had about six subspecies distributed across much of southern and eastern Africa. It, or particular subspecies of it, have also been known as the common zebra, the dauw,Burchell's zebra (actually the subspecies Equus quagga burchellii), Chapman's zebra, Wahlberg's zebra,Selous' zebra, Grant's zebra, Boehm's zebra and thequagga (another extinct subspecies, Equus quagga quagga).

The mountain zebra (Equus zebra) of southwest Africa tends to have a sleek coat with a white belly and narrower stripes than the plains Zebra. It has two subspecies and is classified as vulnerable.

Grévy's zebra (Equus grevyi) is the largest type, with a long, narrow head, making it appear rathermule-like. It is an inhabitant of the semi-arid grasslands of Ethiopia and northern Kenya. Grévy's zebra is the rarest species, and is classified as endangered.

Although zebra species may have overlapping ranges, they do not interbreed. 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. Attempts to breed a Grévy's zebra stallion to mountain zebra mares resulted in a high rate of miscarriage. In captivity, crosses between zebras and other (non-zebra) equines have produced several distinct hybrids, including the zebroid, zeedonk, zony, and zorse. In certain regions of Kenya, plains zebras and Grévy's Zebra coexist, and fertile hybrids occur.