Horse outward similarity is an unreliable measure of relatedness. Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus". Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). Other hybrids include the zorse,
Equus lambei Furthermore, evidence from "E. lambei" mtDNA now proves that modern horses are not so far removed from their ancient ancestors. Many scientists believe that a good argument can be made that "E. caballus", too, should receive protection as a form of native wildlife in North America. However, this topic is still highly debated by wild horse management agencies. This debate has significant implications to wildlife management in North America, including protection and conservation for modern species. Equus lambei Equus lambei (common names include Yukon horse, and Yukon wild horse) is an extinct species of the genus "Equus". "Equus lambei" ranged