Bison

 

This article is about the animal. For other uses, see Bison (disambiguation).

Bison
American bison/American buffalo (Bison bison)
European bison/wisent (Bison bonasus)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Infraclass:	Eutheria
Order:	Artiodactyla
Family:	Bovidae
Subfamily:	Bovinae
Genus:	Bison Hamilton Smith, 1827
Species
†B. antiquus B. bison B. bonasus †B. latifrons †B. occidentalis †B. priscus

Members of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized. The surviving species are the American bison, also known as the American buffalo (although it is only distantly related to the true buffalo), Bison bison (with two subspecies, the plains bison, Bison bison bison, and the wood bison, Bison bison athabascae), found in North America, and the European bison, or wisent (Bison bonasus), found in Europe and the Caucasus. While these species are usually grouped into their own genus, they are sometimes included in the closely related genus Bos, together with cattle, gaur, kouprey and yaks, with which bison have a limited ability to interbreed.

Description

Magdalenian bison on plaque, 17,000–9,000 BCE, Bédeilhac grottoe, Ariège.

The American bison and the European wisent are the largest terrestrial animals in North America and Europe. Bison are good swimmers and can cross rivers over half a mile (1 km) wide. Bison are nomadic grazers and travel in herds. The bulls leave the herds of females at 2 or 3 years of age, and join a male herd which is generally smaller than the female herds. Mature bulls rarely travel alone. Both sexes get together for the reproductive season, towards the end of the summer. American bison are known for living in the Great Plains. Both species were hunted close to extinction during the 19th and 20th centuries, but have since rebounded. The American plains bison is no longer listed as endangered, but the wood bison is on the endangered species list in Canada.

Although superficially similar, there are a number of physical and behavioural differences 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. Adult American bison are not as rangy in build, and have shorter legs. American bison tend to graze more, and browse less than their European cousins. Their anatomies reflect this behavioural difference; the American bison's head hangs closer to the earth 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. American bison are more easily tamed than their European cousins, and breed with domestic cattle more readily.

Genetic history

A 2003 study of mitochondrial DNA indicated four distinct maternal lineages in tribe Bovini:

1. taurine cattle and zebu,
2. wisent,
3. American bison and yak, and
4. banteng, gaur, and gayal.

However, Y chromosome analysis associated wisent and American bison. An earlier study using amplified fragment length polymorphism (AFLP) fingerprinting showed a close association of wisent and American bison and probably with yak, but noted that the interbreeding of Bovini species made determining relationships problematic.

Skulls of European bison (left) and American bison (right)

During the population bottleneck, the number of bison remaining alive in North America declined to as low as 541. During that period, a handful of ranchers gathered remnants of the existing herds to save the species from extinction. These ranchers bred some of the bison with cattle in an effort to produce “cattleo”. Accidental crossings were also known to occur. Generally, male domestic bulls were crossed with buffalo cows, producing offspring of which only the females were fertile. The crossbred animals did not demonstrate any form of hybrid vigor, so the practice was abandoned. The proportion of cattle DNA that has been measured in introgressed individuals and herds today is typically quite low, ranging from 0.56 to 1.8%. In the United States, many ranchers are now utilizing DNA testing to cull the residual cattle genetics from their herds. The U.S. National Bison Association has adopted a code of ethics which prohibits its members from deliberately crossbreeding bison with any other species.

Some cattle breeds are intentionally bred with bison to produce, for instance, Beefalo hybrids. Wisent-American bison hybrids were briefly experimented with in Germany (and found to be fully fertile) and a herd of such animals is maintained in Russia all the time. A herd of cattle-wisent crossbreeds (Zubron) is maintained in Poland. First-generation crosses do not occur naturally, requiring caesarean delivery. First-generation males are infertile.

Behavior

Wallowing is a common behavior of bison. A bison wallow is a shallow depression in the soil, either wet or dry. Bison roll in these depressions, covering themselves with mud or dust. Possible explanations suggested for wallowing behavior include grooming behavior associated with moulting, male-male interaction (typically rutting behavior), social behavior for group cohesion, play behavior, relief from skin irritation due to biting insects, reduction of ectoparasite load (ticks and lice), and thermoregulation. In the process of wallowing, bison may become infected by the fatal disease anthrax, which may occur naturally in the soil.

A group of images by Eadweard Muybridge, set to motion to illustrate the movement of the bison

The bison's temperament is often unpredictable. They usually appear peaceful, unconcerned, even lazy, yet they may attack anything, often without warning or apparent reason. They can move at speeds of up to 35 mph (56 km/h) and cover long distances at a lumbering gallop.

Their most obvious weapons are the horns borne by both males and females, but their massive heads can be used as battering rams, effectively using the momentum produced by 2,000 pounds (900 kg) moving at 30 mph (50 km/h). The hind legs can also be used to kill or maim with devastating effect. At the time bison ran wild, they were rated second only to the Alaska brown bear as a potential killer, more dangerous than the grizzly bear. In the words of early naturalists, they were a dangerous, savage animal that feared no other animal and in prime condition could best any foe (except for wolves and brown bears).

The rutting, or mating, season lasts from June through September, with peak activity in July and August. At this time, the older bulls rejoin the herd, and fights often take place between bulls. The herd exhibits much restlessness during breeding season. The animals are belligerent, unpredictable and most dangerous.

Diet

Bison have a fairly simple diet. The bison's main food is grass. Bison also eat the low-lying shrubbery that is available. In the winter, bison forage in the snow looking for grass. If there is little grass available, bison have to resort to eating the twigs of shrubs.^{[citation needed]}

Predators

Due to their large size, few predators attack bison. However, wolf packs can take down a bison. There are even documented cases of a single wolf taking down bison. Brown bears will also prey on calves, and commonly drive off wolves to take over their kills.

Illness

The main cause of illness in bison is malignant catarrhal fever (MCF).

See also

• African buffalo
• American bison (Bison bison)
• Bison antiquus
• Bison latifrons (Giant bison)
• Gaur
• Wood bison
• Bison hunting
• Great bison belt
• Wisent (European bison, Bison bonasus)
• Yellowstone Park Bison Herd
• Antelope Island Bison Herd
• Antelope Island
• Antelope Island State Park
• Wind Cave Bison Herd
• Henry Mountains Bison Herd
• Henry Mountains
• Book Cliffs

Further reading

• Boyd, D (2003) Conservation of North American Bison: Status and Recommendations. Calgary, Alberta: Master’s dissertation, University of Calgary
• Halbert, N, and Derr, J (1995) A Comprehensive Evaluation of Cattle Introgression into US Federal Bison Herds, Journal of Heredity, Oxford Journals, Vol 98, Issue 1.
• Ward, T. J.; Bielawski, J. P.; Davis, S. K.; Templeton, J. W.; and Derr, J. N. (1999) Identification of Domestic Cattle Hybrids in Wild Cattle and Bison Species: A General Approach Using mtDNA Markers and the Parametric Bootstrap, Animal Conservation

External links

• History of Bison Blend Cattle