The American bison (Bison bison), also commonly known as the American buffalo, is a North American species of bison that once roamed the grasslands of North America in massive herds, became nearly extinct by a combination of commercial hunting and slaughter in the 19th century and introduction of bovine diseases from domestic cattle, and has made a recent resurgence largely restricted to a few national parks and reserves. Their historical range roughly comprised a triangle between the Great Bear Lake in Canada's far northwest, south to the Mexicanstates of Durango and Nuevo León, and east to the Atlantic Seaboard of the United States (nearly to the Atlantictidewater in some areas) from New York to Georgia and per some sources down to Florida.
Two subspecies or ecotypes have been described: the plains bison (Bison bison bison), smaller in size and with a more rounded hump, and the wood bison (Bison bison athabascae)—the larger of the two and having a taller, square hump. Furthermore, it has been suggested that the plains bison consists of a northern (Bison bison montanae) and a southern subspecies, bringing the total to three. However, this is generally not supported. The wood bison is one of the largest wild species of bovid in the world, surpassed by only the Asian gaur and wild Asian water buffalo. It is the largest extant land animal in North America.
There are two extant and four extinct species recognized. Of the four extinct species, three were North American; Bison antiquus, B. latifrons, and B. occidentalis. The fourth; the Bison priscus ranged across steppe environments from Western Europe, through Central Asia, and onto North America.
There are two surviving species; the American bison, Bison bison, also known as the American buffalo, found only in North America, is the most numerous. It is named buffalo although it is only distantly related to the true buffalo. The North American species is composed of two subspecies, the plains bison, Bison bison bison, and the wood bison, Bison bison athabascae. The European bisonBison bonasus, or wisent is found in Europe and the Caucasus, re-introduced after being extinct in the wild.
While all bison species are usually grouped into their own genus, they are sometimes included in the closely related genus Bos, together with cattle, gaur, kouprey and yaks, with which bison have a limited ability to interbreed.