*New anatomical and DNA evidence on the relationship between Artiodactyla (even-toed ungulates) and Cetacea (whales and dolphins) recently led to a merging of the two orders into a new group, Cetartiodactyla (Montgelard, 1997; reviewed in Kulemzina, 2009). As of October 2012, experts had not agreed on whether to define Cetartiodactyla as an official taxonomic order that would replace Artiodactyla and Cetacea. Some continue to list bison in the order Artiodactyla (Franklin, 2011) or use the term Cetartiodactyla without defining it as an order (IUCN, 2008).
Taxonomic History and Nomenclature
Scientific name: Bison comes from the Latin word "bison" meaning "wild ox".
Originally named Bos bison by Linneaus, for its likeness to cattle.
Despite the many anatomical similarities between extinct and modern bison, in 1825 Cuvier distinguished three bison species (McDonald 1981):
living European bison
living North American bison
an extinct American bison
Some 14 North American species were
named prior to 1852 when Leidy studied available specimens and described two fossil species and recognized one living species of bison.
Bison taxonomy underwent a long period of taxonomic splitting that resulted in some 10 fossil species recognized in North America by Skinner and Kaisen in 1947. (McDonald 1981)
This taxonomy in great need of revision and clarification (McDonald 1981) (Prusak et al 2004)
Some authorities have classified bison with the cattle genus Bos, other authorities do not. (Nowak 1999) (Prusak 2004)
Relationship of modern American bison and the European bison is unclear at present, but both are quite similar genetically and can interbreed; despite this fact, they should still be considered separate species. (Prusak et al 2004)
Modern North American bison have two recognized subspecies: the American Plains Bison (B. b. bison) and the American Wood Bison (B. b. athabascae). (McDonald 1981)
(Prusak et al 2004)
Even-toed hoofed mammals trace their ancestry back to at least 45 million years ago (Eocene).
Bison diverged from cattle a few million years ago or less; phylogenies are
poorly understood due to much genetic variation within species. (Buntjer et al 2002)
The Bison genus first appeared in southern Asia, around 2 million years ago (McDonald 1981)
Bison priscus was the ancestor of at least some of the North American bison.
(Prusak et al 2004)
This species flourished in northern Eurasia and Alaska and may have been the dominant hoofed mammal there (Guthrie 1970)
Bison immigrated to North America several times in the Pleistocene Epoch during times of low sea levels when exposed land connected North America and Asia.
B. latifrons appeared by 500,000 years ago in North American and survived until around 20,000 years ago.
The first appearance of B. antiquus in North America was around 250,000 years ago. (Jefferson 2001)
The B. antiquus line may have led to modern American Plains Bison (Prusak et al 2004)
McDonald (1981) suggests this speciation occurred around 5,000 years ago.
European bison may be descendants of Pleistocene bison that returned to Europe from North America.
(McDonald 1981) (Prusak et al 2004)
B. latifrons became extinct around 20,000 years ago. (McDonald 1981)
All bison nearly became extinct in North America at the end of the Pleistocene when much of the other megafauna did become extinct
Modern bison in America (Bison bison) and Europe (Bison bonasus) are genetically very closely related. (Prusak et al 2004)
DISTRIBUTION & HABITAT
(McDonald 1981) (Meagher 1986) (Nowak 1999)
Distribution (of North American bison)
American bison historical distribution. Click on map
for current detailed distribution (IUCN).
Teeth high crowned (hypsodont) and cresent-cusped ("moon tooth" or selenodont)
All deciduous teeth present at birth
First permanent tooth erupts during first year
In general, more luxuriant and longer than the European bison (Nowak 1999)
Brown; appears black from a distance
Head, underbelly, flanks, and rear are dark brown
Longest hairs on forelegs and beard
Males swing their "pantaloons" in threat displays (Lott 1974)
Thick mat of hair on the male's forehead helps protect from the head-clashing impacts (Guthrie 1990)
Winter coat is wooly under fur overlain
by coarse guard hairs; this hair bleaches to tan
Molt begins in late winter/early spring
Heavier, denser, and finer pelage than in many cattle
Have ten times the number of cattle's primary hairs per square inch
Pelage enables these animals to withstand subzero, windy winters
Short eyelashes compared to cattle help keep their eye lids from accumulating ice
Young are much lighter colored than adults.
This difference follows a general rule for young of animals that live in large groups in open environments where the young need to be protected.
European bison (B. bonasus) living in smaller groups have young that are colored more like the adults.
Males up to two-thirds larger than females with stouter, more robust and evenly curving horns, a much larger hump, longer pelage, and a thicker neck.
Considering fossil species of bison and the two species living in North America and Europe today, Bison bison bison has a moderate amount of sexual dimorphism, the European Bison bonasus a low amount, and the fossil Steppe Bison had extreme dimorphism, especially in the size of the skull. (Guthrie 1990)
Other Physical Characteristics
Acute sense of smell
Good eyesight; can recognize objects the size of a horse with a rider at 1 km (.6 mi)
and moving objects at 2 km (1.2 mi). (McHugh 1958)
Strong head-to-head impacts from dominance fighting between bulls are made less damaging to the brain by a system of bone struts which divide the inner and outer walls of the skull. (Guthrie 1990)
Broadside threat posture displays give best view of overall large body size; may intimidate opponents into submission (Lott 2002)
Bulls may bellow when threatening each other.
This sound has been compared to a lion's roar and can be heard up to 5 km (3 mi) away. (Meagher 1986) (Buchholtz & Sambraus 1990)
Males that are competing with each other may wallow, then urinate in the wallow and roll in the urine before resuming their challenges (Lott 2002)
Females have also been observed urinating into wallows and rubbing their necks on the soil.
Bulls use a lip curl and tongue (flehmen) to transfer cow's hormone-packed urine to a receptor organ in the roof of his mouth. (Lott 2002)
Gaits include walking, trotting, galloping, bounding. (McHugh 1958)
Can run up to 60 km/hr (35 mph)
Known to leap over barbed wire fences; surprising agility for animal its size
Good swimmers; can swim rivers at least 1 km (.6 mi)
wide. (Meagher 1986)
Bison grazing in Flint Hills of Kansas increased abundance of Upland Sandpipers, Grasshopper Sparrows and together with the effects of recent prescribed burnings, lowered numbers of Dickcissel. (Powell 2006)
Human prescribed burning plus intense bison grazing may lower numbers of four grass-dependent species of sparrows and Eastern Meadowlarks, and shrub-dependent Bell's Vireos. (Powell 2006)
After grazing by bison, there are fewer plants, but more species; grazing increases diversity of grassland species, as does a fire. (Lott 2003) (Powell 2006)
Grazing bison keep grasses short, which promotes prairie dog colony survival; prairie dogs don't live in areas with tall grass where they can not see approaching predators. (Lott 2003)
Bison are attracted to bare dirt for dusting fur in prairie dog towns.
Brown-headed cowbirds (Molothrus ater) forage on insects disturbed by grazing bison.
Sedges and rushes (water loving plants) grow in compacted bison wallows that can hold extra rainfall. (Lott 2003)
Many other ungulates co-exist with bison using different foraging techniques and plant preferences
Native Americans living in bison habitats depended on bison for much of their subsistence.
Bison fertilize the grasslands.
DIET & FEEDING
(Guthrie 1990) (Hawley et al 1981) (Peden et al 1974)
Bison are grazers; feed mostly on grasses.
Winter/summer diets differ in free-ranging populations.
Add lichens and mosses to diet in winter.
When feeding on natural vegetation select many different grass and a few other plant species, varying with local habitats (Peden et al 1974)
Blue gramma (Bouteloua gracilis), sand dropseed (Sporobolis cryptandrus) little bluestem (Andropogon), windmill grass (Chloris), wild oats (Avena), wheatgrass (Agropyron), and Bromus Hierchloe, Elymus, Koeleria, Stipa, Phragmites, Distichlis, Hordeum, and Carex.
In Arizona bison ate 71% saltbush (Atriplex sp.) (Peden et al 1974)
Ruminant digestive system; four chambered stomach
Compared to cattle, bison extract more nutrition from low protein, highly fibrous plants. (Hawley 1981).
European bison have more browse in their diet in the wild. (Peden et al 1974)
Because American bison males in the wild lived mostly apart from the large herds, they were able to select the better-quality food and grow to very large size. (Guthrie 1990)
REPRODUCTION & DEVELOPMENT
(Berger 1992) (Buchholtz & Sambraus 1990) (Rutberg 1986) (Komers et al 1994) (Lott 2002) (Meagher 1986) (McDonald 1981) (Mooring et al 2006) (Nowak 1999) (Weigl 2005)
June - September for breeding season
Males, both solitary and ones from male groups, join females in breeding season (Buchholtz & Sambraus 1990).
Males are in rut approximately four weeks July-August (Mooring et al 2006)
A female about to be receptive may run through the herd, attracting the attention of males who compete for rights to tend (Lott 2002)
Fewer than 10,000 animals in free-ranging populations (Lott 2003)
Bison bison is near threatened with stable population trends. (IUCN Red List 2008);
Version 3.1 (http://www.iucnredlist.org/search
CITES Status: (Subspecies athabascae only) Appendix I as of 07/01/75 - Endangered, no international trade; Appendix II as of 09/18/97 - Not now threatened but may become so if trade not controlled. (97http://www.cites.org/eng/resources/species.html)
Threats to survival
Hunting in 1800 and 1900's nearly exterminated bison in North America.
Their gene pool experienced a bottleneck but genetic diversity hasn't declined significantly.
Some researchers argue that bison will increasingly be eradicated by genetic modification as they are domesticated.
Over 90 percent of bison in North America are "undergoing domestication'" (Lott 2002)
Cattle genes found in nearly more than half of public herds in the U.S. and Canada and in all but one of 50 sampled private herds. (Halbert & Derr 2007)
Important Web Resources:
Center for Bison Studies at Montana State University - Bozeman: This website offers many links to books and articles about bison.