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The taxonomic record (above) is taken from Wilson and Reeder (1993). Some authors consider Bison bison and B. bonasus to be conspecific, grouping the two into a single species (Nowak, 1991). The taxonomic status of the genus Bison is also disputed, with some authorities placing it as a subgenus of Bos (Nowak, 1991). Two subspecies are generally recognized, the wood bison, B. b. athabascae of northern Canada, and the plains bison . B. b. bison, the great plains of southern Canada and the central United States. Invalid synonyms include americanus, athabascae, haningtoni, montanae, oregonus, pennsylvanicus, and septemtrionalis (Wilson and Reeder, 1993).
Click on the pictures above for a larger view of the photographs
Body Length: up to 380 cm / 12.5 ft
Shoulder Height: up to 195 cm / 6.5 ft.
Tail Length: 90 cm / 3 ft.
Weight: 545-818 kg / 1200-1800 lb.
The dark brown coat is long and shaggy on the forequarters, including the front legs, neck, and shoulders (individual hairs may be up to 50 cm / 20 inches long). On rare occasions the coat is gray, speckled or cream coloured. Calves are born a light reddish brown colour, but generally change to dark brown by 6 months of age. Males may be up to 1/3 larger than females. On the forehead, the hair is woolly and curly, giving the head a mop-like appearance between the horns. There is a beard beneath the chin. The shoulders are massive and humped, with the head carried low. The short horns are present in both sexes and arch backwards, outwards, and then upwards, curving slightly in at the blunt tips.
Ontogeny and Reproduction
Gestation Period: 270-300 days.
Young per Birth: 1, rarely 2.
Weaning: 5-6 months.
Sexual Maturity: Between 2-3 years.
Life span: Up to 25 years.
The breeding season is in August, when smaller herds join to form a group with up to 400 animals milling around. Females are very protective of their young, and few predators are willing to face a mad mother bison.
Ecology and Behavior
Due to their bulk and the climate in which they live, bison may be active at any hour, although there appears to be a preference for daylight hours. Most feeding occurs in the early morning and around dusk. Daily movements of around 5 kilometers / 3 miles are average, with a group circulating in a home range 30-100 square kilometers in size depending on the season. In addition, certain populations make large scale migrations, moving up to 250 kilometers / 150 miles from higher, more northern areas, to sheltered valleys and lowlands in the autumn, and back again in the spring. During winter, bison will paw away in deep snow to reach the dried shrubs hidden underneath. Grooming is a surprisingly frequent activity among bison, with animals rubbing themselves on trees until all of the bark has been torn off, and the trunk left smooth. Dust baths in loose patches of soil are apparently a favourite activity, although the large hump on the shoulders generally means that the animal must get up and switch sides instead of rolling over. Despite their size, bison are accomplished athletes, able to run at speeds of up to 50 kmph / 30 mph and swim rivers over 1 kilometer / 0.6 miles wide. During the breeding seasons males will bellow - a sound which may carry up to 5 kilometers / 3 miles.
Family group: Herds of females and their young (generally less than three years old) with about 60 animals, bulls are found in smaller bachelor herds or are solitary.
Diet: Prairie grasses, in winter lichens and mosses.
Main Predators: Humans.
Prairies and woodlands in isolated pockets through midwestern Canada and the United States.
Countries: Canada, United States (IUCN, 2002).
Range Map (Redrawn from Burt and Grossenheider, 1976)
The American bison is classified as a low risk, conservation dependent species by the IUCN (2002). Only the wood bison, Bison bison athabascae, is listed on Appendix II of CITES (CITES, 2003).
Mentioned in the famous (and misleading) song "Home on the Range", this large relative of cattle is often incorrectly called a 'buffalo' ["Oh give me a home where the buffalo (*bison) roam, where the deer and the antelope (*pronghorn) play..."]. However, true buffalo inhabit the Old World continents of Africa and Asia, and are of an entirely different morphology than bison.
The American bison has one of the most dramatic stories regarding human impact on the environment. In the seventeenth century, an estimated 60 million bison roamed the plains of North America. With the arrival of settlers, the bison were pushed out of their native land and ruthlessly hunted - until, by 1890, less than 1,000 animals survived. Unlike the native Americans, who had traditionally hunted the bison for food, tools, and their hides, the European's slaughter was primarily for sport, with people shooting from the newly built railway, seeing how many they could kill in a day. With fortuitous foresight, the American Bison Society was formed in 1905 to secure the survival of this species. With the help of captive breeding and reintroductions to the wild, the American bison population is now relatively secure, with 500 thousand animals.
Bison (Latin) a bison. Also bison (Greek) a species of wild ox, the hump-back ox, bison.
- Bison américain (Buchholtz, 1990)
- Amerikanischer Bison (Buchholtz, 1990)
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CITES (Convention on the International Trade in Endangered Species of Wild Flora and Fauna). 2003. Appendix II, as adopted by the Conference of the Parties, valid from 13 February 2003. Available online at http://www.cites.org/eng/append/latest_append.shtml
IUCN ( International Union for Conservation of Nature and Natural Resources). 2002. 2002 IUCN Red List of Threatened Species. Available online at www.redlist.com
Nowak, R. M. [editor]. 1991. Walker's Mammals of the World (Fifth Edition). Baltimore: The Johns Hopkins University Press.
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