Equus (genus)

Equus is a genus of mammals in the family Equidae. It includes horses, asses, and zebras. Equus is the only living (extant) genus of horses, and there are seven living species. They are the one-toed horses, and are adapted for living in various types of grasslands.

The term equine refers to any member of this genus. Equus has many extinct species known only from fossils. The genus most likely originated in North America and spread quickly to the Old World. Equines are odd-toed ungulates with slender legs, long heads, relatively long necks, manes (erect in most subspecies) and long tails. All species are herbivorous, and mostly grazers with simpler digestive systems than ruminants. They can live on low-quality vegetation.

Feral equine populations are widespread, but wild equines are found only in Africa and Asia. Wild populations may have a harem system. In this case one adult male or stallion, several females or mares and their young or foals. Otherwise they live in a territory where males control territories with resources that attract females. In both systems, females take care of the foals, though males may play a role as well. Equines communicate with each other visually and vocally. Human activities have threatened wild equine populations and out of the seven living species, only the plains zebra is still widespread and abundant.

The one-toed horses of the grasslands developed from smaller three-toed horses which lived more in forests and wooded savannahs. Before the coming of humans, horses were much more varied and widespread, though the number of species is not known.

Living horses

There are seven species of living horses in the wild. They are:
E. africanus—African wild ass
E. ferus—wild horse
E. grevyi—Grévy's zebra
E. hemionus—onager
E. kiang—kiang
E. quagga—plains zebra
E. zebra—mountain zebra

This is not counting the many types of horse which mankind has modified by breeding. Equus ferus has been the species used by man as the basis of the various breeds of horse.