Description

The American bison and the European bison (Wisent) are the largest surviving terrestrial animals in North America and Europe. Bison are good swimmers and can cross rivers over half a mile (800 meters) wide. They are nomadic grazers and travel in herds. The bulls leave the herds of females at two or three years of age, and join a male herd, which are generally smaller than female herds. Mature bulls rarely travel alone. Towards the end of the summer, for the reproductive season, the sexes necessarily commingle.^[4] American bison are known for living in the Great Plains, but formerly had a much larger range including much of the eastern United States and parts of Mexico. Both species were hunted close to extinction during the 19th and 20th centuries, but have since rebounded; the Wisent owing its survival, in part, to the Chernobyl Disaster, ironically, as the Chernobyl Exclusion Zone has become a kind of wildlife preserve for Wisent and other rare megafauna such as the Przewalski's Horse, though poaching has become a threat in recent years.^[5] The American Plains bison is no longer listed as endangered, but this does not mean the species is secure. Genetically pure B. b. bison currently number only ~20,000, separated into fragmented herds - all of which require active conservation measures.^[6] The Wood bison is on the endangered species list in Canada^[7] and is listed as threatened in the United States, though there have been numerous attempts by beefalo ranchers to have it entirely removed from the Endangered Species List.^[8]
Although superficially similar, physical and behavioural differences exist between the American and European bison. The American species has 15 ribs, while the European bison has 14. The American bison has four lumbar vertebrae, while the European has five.^[9] (The difference in this case is that what would be the first lumbar vertebra in wisent has ribs attached to it in American bison and is thus counted as the 15th thoracic vertebra, compared to 14 thoracic vertebrae in wisent.) Adult American bison are less slim in build and have shorter legs.^[10] American bison tend to graze more, and browse less than their European relatives. Their anatomies reflect this behavioural difference; the American bison's head hangs lower than the European's. The body of the American bison is typically hairier, though its tail has less hair than that of the European bison. The horns of the European bison point through the plane of their faces, making them more adept at fighting through the interlocking of horns in the same manner as domestic cattle, unlike the American bison, which favours butting.^[11] American bison are more easily tamed than their European cousins, and breed with domestic cattle more readily.^[12]