Bos bison Linnaeus 1758
Creators: name: Don E. Wilson
name: Russell A. Mittermeier
Publisher: name: Lynx Edicions
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Artiodactyla
Bovidae
Bos
Bos bison

description: 5.
American Bison
Bos bison
French: Bison d’Amérique / German: Bison / Spanish: Bisonte americano
Other common names: Buffalo; Plains Bison (bison), Wood Bison (athabascae)
Taxonomy. Bos bison Linnaeus, 1758,
Mexico (= C Kansas, Quivira). Restricted by Hershkovitz in 1957 to C Kansas, “Quivira.”
Sometimes included in the genus Bison. Most recognize two subspecies of American Bison based on physical differences in body mass, horn size, diameter of horn cores, hump configuration, and foreleg chaps. Because of mixing of the “Plains Bison” (bison) with the “Wood Bison” (athabascae) in northern Canada in the 1920s, populations of Wood Bison are no longer genetically pure, but they do retain many of their taxonomic characteristics and other differences from Plains Bison and can be distinguished completely by six horn and five cranial measurements. Two subspecies recognized.
Subspecies and Distribution.
B.b.bisonLinnaeus,1758—scatteredinfree-rangingconservationherdsinW&CCanada(BritishColumbia&Saskatchewan),WUSA(Alaska,Montana,Utah&Wyoming),andextremeNMexico(Chihuahua).
B. b. athabascae Rhoads, 1898 — scattered in free-ranging conservation herds in W & C Canada.
Descriptive notes. Head-body 304-380 cm (males) and 210-350 (females), tail 43-60 cm, shoulder height 167-195 cm (males) and 150-180 cm (females); weight 460-998 kg (males) and 360-544 kg (females). American Bison are the largest terrestrial herbivores in North America, massively built, tall, and rather narrow in head-on profile. Although the two subspecies, Plains Bison and Wood Bison, share common characteristics, individuals in extant populations are disparate in some diagnostic ways. Compared to Plains Bison, Wood Bison weigh more; they have a longer body, legs, and horns; wider and longer pelvis; and greater basal skull length but smaller skull width on the masseteric processes. The hump of the Wood Bison is more abrupt and taller anteriorly, whereas the Plains Bison has a deeper neck from which the hump rises gradually and does not decline as much behind. Both subspecies have a dense darkbrown coat, appearing black from a distance, with shaggy, long, and nearly black hairs on the cape, neck, shoulders, and front legs (more so in Plains Bison with its well-developed chaps). Some color variation exists seasonally; for example, when the pelage bleaches from exposure to the sun. Young are born reddish-tan but become brownishblack at about three months of age. The hairs on the dark head are curly and moplike between the horns of Plains Bison, often obscuring the lower parts of the horn; on Wood Bison, they are straight and extend farther down the face, rarely obscuring the horns. Both subspecies have ventral beards, but they stand out more and appear more pointed in Wood Bison. The dorsal cape of Plains Bison is well defined and yellow-ocher in color, with a sharp demarcation between it and the rest of body—not so in Wood Bison. Plains Bison tend to hold their heads lower than do Wood Bison, and the hindquarters of Plains Bison are smaller and more gradually sloping. Both sexes have relatively short, blunt-tipped black horns that project backward, outward and then curve upward; the horns are pointed outward a bit more in Wood Bison. The horns of females tend to curve inward at the top and are smaller than those of males. Dental formula is 10/3, C0/1, P 3/3, M 3/3 (x2) = 32. Molars are hyposodont and selenodont; the first permanent teeth erupt after one year of age, and all permanent teeth are present by age five.
Habitat. The American Bison is decidedly a species of relatively uniform and low-lying North American grasslands and meadows; however, historical evidence shows thatit once roamed to elevations of 3200-3900 m in Colorado, Wyoming, and Montana, USA. American Bison tolerate a wide range of climate and habitat conditions; they once occupied semi-arid grasslands of Mexico and the southern USA, grasslands of more moderate climate but huge variability in precipitation and temperatures in the central USA, eastern forested areas in the USA, and cold boreal spruce forests in Canada and Alaska. Population densities no doubt varied by location. In forested areas in Canada and the eastern USA, openings and wetland meadows were no doubt important habitats; riparian areas along streams and rivers provide abundant sedges. Although use of forested areas is limited, American Bison will seek such cover for shade and during inclement weather in winter. Habitat use by American Bison is determined by a complex combination of tradition, occasional need for shelter, food and nutrient availability, access to water, and freedom from insect harassment. American Bison are strong swimmers and not deterred by swift rivers or lakes while moving from one area to another.
Food and Feeding. The American Bison is herbivorous and much more of a grazer than its European counterpart. American Bison eat grasses and sedges in all seasons, and are not particularly selective of particular species given its large mouth size. Sedges dominate diets in northern areas with abundant wet meadows, and cool-season and warms-season grasses are important in mixedand short-grass prairies, respectively. It is not uncommon for diets of American Bison to contain 95% grasses and sedges, but in semi-arid areas where grass/sedge availability is seasonally low, browse and forbs are important and movements to acquire them typically increase. Snow is readily swept away by the head as American Bison search for grasses/sedges in winter. Fires can play a significant role in habitat selection. In the past, fires deliberately set by humans likely caused American Bison to move to such areas to take advantage of the flush of grasses and herbaceous species that follow fires. Many prairie habitats in the USA currently are managed with fire, and if American Bison are present, groups gravitate to such areas. American Bison are more efficient at digesting low-quality diets than domestic cattle (B. taurus) and often sympatric Wapiti (Cervus canadensis). Water availability is important to American Bison, and they readily consume free-standing water and snow.
Breeding. The breeding and birthing seasons of American Bison are late June-September and mid-April-May, although conceptions may be more punctuated because births in some populations occur over just a couple of weeks. Northern populations generally give birth a couple of weeks later than southern populations. Some males stay with female herds throughout the year, but others, particularly mature males,live alone or in bachelor groups of 2-6 individuals until rut. Males attain their maximum breeding performance at 6-9 years old and establish dominance by displaying and fighting each other to attain breeding rights, which are not simply a function of age and weight. Rutting males are boisterous and very active during rut, when overall herd size increases. While a dominant male tends an estrous female, both sexes may lick and horn each other, and females may even try to mount the bull. Copulation, which is typically crepuscular or occurs at night, is abrupt and of short duration; the pair may start to run off together before copulation ends. Females are seasonally polyestrous. They breed for the first time at two years of age and give birth in their third year. Calving rates of sexually mature females vary by location but can be as high as 88%; typically, a mature female will produce two calves every three years. Female American Bison are most productive between three and 12-15 years. Males maylive to their late twenties in captivity but likely less than 20 years in the wild. Females may live up to 29 years in captivity, but as with males, they are no doubt shorter-lived in the wild. Gestation is about 285 days; sex ratio at birth is somewhat male biased. American Bison have one calf at a time, very rarely twins. Females may give birth in the herd or retire to an isolated location. Neonates are 15-25 kg at birth; they are precocious, standing about only ten minutes after birth and nursing after about 30 minutes. The young will begin to test solid food and drink water at about 5-7 days of age but nurse for 7-8 months; weaning occurs at about one year of age, at which time young weigh 225-315 kg.
Activity patterns. American Bison are primarily diurnal, occasionally feeding and traveling at night. Daily activity patterns are typical of ruminants, involving waves of foraging followed by ruminating/resting. Both sexes and all age classes wallow usually in dry depressions that are deepened by regular and frequent use; wet wallows are sometimes used. Horning of vegetation by both sexes is also a common activity.
Movements, Home range and Social organization. The American Bison has been described as migratory and nomadic. Historically, these animals undertook lengthy movements, often single-file, but given the unpredictability in weather across much of their former range, most populations tended to be nomadic because of uncertain forage availability in any given season or location. Where resources were more predictable, American Bison may have migrated from a regular summer range to a regular winter range and back again. Such movements could be directional, elevational, or both. Distances moved vary greatly and depend on the extent of usable range; daily movements of several kilometers are typical, but over a year, individual Wood Bison may traverse an area of more than 1400 km ®. On Santa Catalina Island, California, where the total amount of usable habitat is limited, annual home range sizes of females were 29-5-70-5 km?, similar to those in the Henry Mountains, Utah, that averaged 52 km *. American Bison are very gregarious and occur in three types of groups: matriarchal, male only, and mixed breeding. In Yellowstone National Park, average group sizes range from 10-63 individuals in matriarchal groups to 19-480 individuals in mixed breeding groups. Groups of American Bison are rather fluid and are made up of females, their offspring, and 2-3 year olds and a few older males. Bonds between females and their male and female offspring may last into their second and third years, respectively, but offspring become quite independent as young as 2-3 weeks, and cluster together in bands of 2-15 within their matriarchal group. Today’s groups are just a vestige of the huge herds that were typical throughout much of the historical range of the American Bison.
Status and Conservation. CITES Appendix II (Wood Bison only). Classified as Near Threatened on The IUCN Red List. American Bison once ranged from Mexico through the Intermountain West of the Rocky Mountains to Alaska, east through the Great Plains, south of the Great Lakes and east to the Allegheny Mountains in Maryland, and south to Georgia and northern Florida (although the specific eastern extent of the historic range is still disputed). The species attained its numerical zenith in the fertile Great Plains of the USA and Canada. As settlement by Europeans advanced westward in the midto late 1880s, the near extermination of bison in North America from rampant market hunting for meat and hides, regional drought, competition with livestock, and likely introduced bovine diseases has been well documented. There also was a concerted effort by the US military to exterminate bison and thereby handicap Native Americans dependent on them. Perhaps no other wild mammal experienced such a rapid and complete reduction in numbers and range, from tens of millions to as few as 500-1000 individuals by the late 1880s. Only remnant wild populations of Plains Bison and Wood Bison existed then in Yellowstone National Park, USA, and northern Alberta and Northwest Territories, Canada. Unfortunately because of early translocations of Plains Bison into northern Canada, interbreeding there resulted in genetically impure Wood Bison; however, theystill display most of their unique phenotypic char acteristics that contrast pure Plains Bison. Similarly, some Plains Bison, such as those in Custer State Park, South Dakota, USA, are infused with domestic cattle genes. Bold conservation efforts initiated by W.'T. Hornaday in the 1890s and championed thereafter by numerous other individuals and agencies/organizations saved wild Plains Bison and Wood Bison from possible extinction. Today, free-ranging and semi-free Plains Bison and Wood Bison occur in 62 and eleven “conservation herds,” only totaling about 20,500 and 10,900 individuals, respectively; semi-free herds are confined to some degree and perhaps given supplemental feed. Eight of those herds, five Plains Bison and three Wood Bison, have more than 1000 individuals, with one Plains Bison herd (Greater Yellowstone area, north-western Wyoming and south-western Montana) and one Wood Bison herd (Greater Wood Buffalo National Park area, north-eastern Alberta and south-central Northwest Territories, Canada) numbering more than 5000 individuals. Five free-ranging conservation herds of Plains Bison occur in their native range: one in Canada (Prince Albert National Park, central Saskatchewan), three in the USA (Henry Mountains, Utah; Grand Tetons, Wyoming; and Greater Yellowstone area), and one in Chihuahua, Mexico, which moves across the international border into New Mexico, USA, whereit is officially considered livestock. An additional five free-ranging Plains Bison herds have been introduced outside of their native range: one in the Pink Mountains, British Columbia and four in Alaska (DeltaJunction, Copper River, Chitina River, and the Farwell area), where variable harvests are regulated by state and provincial game agencies. Ten free-ranging conservation herds of Wood Bison occur in western Canada, with an additionalfledgling introduction in Alaska. In the USA, semi-free conservation herds of Plains Bison occur in Montana, North Dakota, Minnesota, Wisconsin, Wyoming, South Dakota, Nebraska, Iowa, Illinois, Utah, Colorado, Kansas, California, Arizona, Oklahoma, Texas, and Kentucky; no Wood Bison conservation herds are considered semi-free in Canada. Commercial herds, officially considered domestic by most governmental agencies, number about 500,000 bison (mostly Plains Bison) on about 4000 privately owned properties, but they do not have a role in the conservation and recovery of the wild populations. A consortium of Native American tribes is working to restore “buffalo to Indian Country.” Plans are underway to establish large free-ranging herds of Plains Bison in Colorado and northern Montana and Wood Bison in Alaska. The IUCN American Bison Status Survey and Conservation Guidelines 2010 calls for restoration of the species on an ecological scale comparable to its historical past. Assembling the large landscapes required for such restoration will have to involve innovative approaches to deal with ecologically degraded areas, legal rights of private and public stakeholders, and prevailing socio-economic conditions. Substantial financing will be needed for planning, implementation, and maintenance to ensure the success of such a bold endeavor.
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description: Published as part of Don E. Wilson & Russell A. Mittermeier, 2011, Bovidae, pp. 444-779 in Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona :Lynx Edicions on pages 577-579, DOI: 10.5281/zenodo.6512484