Bison bison is a member of the Bovidae or bovine family. The weight of the bison is approximately 1 tonne (2,200 lbs), earning the title of largest mammal of North America. The shoulders of the plains bison are at 6 to 6.5ft high and the body is 10 to 12.5ft long, the males typically larger than the females. The lifespan in the wild is between 18 and 22 years, up to 30 years in captivity. There are two subspecies of B. bison: the wood bison in northern Canada and plains bison historically inhabiting much of the continent. The plains bison has a large head with relatively small, curving horns. The coat is dark brown and shaggy on the forequarters (front legs, neck and shoulders) while the rest of the body has shorter fine hair. The diet of bison consist mainly of grasses and sedges.
The numbers of this large animal were so great, that migration was considered the greatest natural spectacle humans observed and was described as ‘an ocean of black dots.’ As a keystone species, the large range in combination with the grazing pressure helped shape the ecology of the Great Plains. The bison move continuously as they eat so an area is rarely overgrazed.
To the plains Indians of North American, the Bison was very important to survival, as well as greatly respected.
The existence of B. bison was not threatened until Europeans arrived and the populations dwindled from 50 million to less than 800 due to over hunting. Protection and management of the species has allowed the populations to rebound to approximately 40,000 individuals. Professional hide and meat hunters from Europe greatly contributed to this over hunting, slaughtering by the millions. The tongue was considered a delicacy, and often the animal was slaughtered solely for this item. Though by 1884 the populations were nearly decimated, reserves were declared and the animal was being federally protected. Refuges include: Yellowstone National Park, Wood Buffalo National Park, Witchita Mountains Wildlife Refuge. Yellowstone National Park has the largest population of free-roaming plains bison at 4,000 and Wood Buffalo National Park has the largest population of free-roaming wood bison at 10,000. A dramatic consequence of the reduced populations is inbreeding depression.
All photos were taken in Yellowstone National Park during the fall of 2009.
Cogger, H.G., E. Gould, J. Forshaw, G. McKay and R.G. Zweifel (1993) The Encyclopedia of Animals. Fog City Press, San Francisco, California.
Kays, R.W. and D.E. Wilson (2009) Mammals of North America. Princeton University Press, Princeton, New Jersey.