Genetics says the bison is really a kind of cattle
Taxonomists long kept bison in a genus of their own, separate from cows, yaks and gaur. DNA studies in the 2010s broke that neat arrangement: both living bison species sit so deep inside the cattle family tree that the only consistent fix was to fold Bison into Bos as a subgenus.
Bos, Latin for cow or ox, covers wild and domestic cattle. Counted the traditional way it holds five living species; treat the domestic forms as distinct and the tally reaches eight, and adding bison makes ten. Most domestic breeds, both taurine cattle and the humped zebu, are thought to descend from the extinct aurochs, though Bali cattle and gayal have other wild ancestors. About 1.3 billion domestic cattle are alive now, which puts them among the most numerous mammals anywhere.
Those paired wild and tame forms created a naming headache. Older names had sometimes been given to the domestic animal before its wild ancestor. In 2003 the International Commission on Zoological Nomenclature settled the matter by preserving 17 names based on wild species, so the aurochs stays Bos primigenius and the gaur keeps Bos gaurus, while allowing Bos taurus and Bos frontalis whenever domestic cattle and gayal are treated as separate species.
The bison result had its own twist. Nuclear DNA showed the two living bison as each other's closest relatives, with yaks as their nearest kin within Bos. Yet the European wisent's mitochondrial DNA pointed instead towards cattle, contradicting the nuclear picture, while the American bison's matched it.
In the wild these ruminants break down tough plants with four-chambered stomachs, live 18 to 25 years, and carry young for 9 to 11 months. Herds of ten to thirty usually have a single bull, and calves tend to inherit their mother's rank. Where people encroach, some herds switch to night activity. One wild species, the kouprey, last seen in 1969, is probably extinct.
Source: Bos
