The Bison



About The Bison
Bison are large, even-toed ungulates in the genus Bison within the subfamily Bovinae. Two extant and six extinct species are recognised. Of the six extinct species, five went extinct in the Quaternary extinction event. Bison palaeosinensis evolved in the Early Pleistocene in South Asia, and was the evolutionary ancestor of B. priscus (steppe bison), which was the ancestor of all other Bison species. From 2 MYA to 6,000 BC, steppe bison ranged across the mammoth steppe, inhabiting Europe and northern Asia with B. schoetensacki (woodland bison), and North America with B. antiquus, B. latifrons, and B. occidentalis. The last species to go extinct, B. occidentalis, was succeeded at 3,000 BC by B. bison.

Behaviour
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.

Bison 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 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 what is a typical weight of 2,000 pounds (900 kg) (can be up to 2700 lbs) moving at 30 mph (50 km/h). The hind legs can also be used to kill or maim with devastating effect. In the words of early naturalists, they were dangerous, savage animals 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.

Reproduction
Female bison typically do not reproduce until three years of age and can reproduce to at least 19 years of age. Female bison can produce calves annually as long as their nutrition is sufficient, but will not give birth to a calf after years where weight gain was too low. A mothers’ probability of reproduction the following year is depends strongly on mother mass and age. Heavier female bison produce heavier calves (weighed in the fall at weaning) than light mothers, while the weight of calves is lower for older mothers.

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