American bison is a big ungulate mammal with black and circular hooves. The color of fur varies in the front and back of its body and is different shades of brown. Bison is hunchbacked and it has a long beard on its chin. The forehead is wide and narrow while the neck is short. Hind legs are smaller than front legs, making up a scarp from humpback to tail. Length of hair differs in front and rear, especially in males: front hair is significantly longer than rear hair. Horns of bison are black, bent inward withal upward and pointed.
In the past, a huge number of bison thundered North America from Mexico to Alaska. Then, mass killings of these impressive animals led to their total extermination from the main area of their habitat. However, bison survived and currently they live primarily in Canada and the western part of the USA, usually in protected areas and national parks. American bison prefer to inhabit river valleys, and prairies, and plains. Typical habitat is open or semiopen grasslands, as well as sagebrush, semiarid lands, and scrublands. Bison also graze in hilly or mountainous areas where the slopes are not steep.
American bison is diurnal, being active all day long. They are usually relatively passive during the day, becoming particularly active at dusk and dawn. They spend a lot of time cleaning the fur or grooming: they rub their head, sides, and necks against trunks of trees. Bison are able to be constantly on the move, passing long distances as long as there is food. Cows, female bison, are leaders of family groups while males stay separate, creating small groups or living solitarily. As the mating season comes, males join female groups. Bison like rolling, weltering, and rubbing against the ground. Wallows are recesses - dust bowls with no vegetation, having circular form, formed as a result of bison’s wallowing on the ground.
Bison are herbivores (graminivores) and, more specifically, grazers, chewing grass all year round. However, in absence of grass, they eat other greenery found in the area such as sagebrush. The presence of water is another important component of their life: they can’t last long without a source of water.
Bison are polygynous, meaning that a dominant male, or a bull, mates with a group of females. The season for breeding takes place in summer, from June to September while the gestation period lasts about 285 days. A female can give birth to a single calf each season. Newborn calf weight about 15-25 kg. To give birth, bison females choose shelter, a distant place far from the herd. Protection of calf lies on the shoulders of females whereas males don’t take part in this process. Babies are breastfed for 7-8 months and weaned when they are one year old. Males reach sexual maturity at the age of 3 years and females - from 2 to 3 years.
The most notable threats to the population of this species as a whole are long-time persecution of bison from their habitat; slow growth of population in closed and protected areas; genetic manipulation in commercial purposes; hybridization and back crossing of bison and other cattle as well as between different bison subspecies; natural limiting factors in conditions of reservations; and the possible threat of depopulations of bison because of its wild populations’ carrying cattle deceases; continuous culling of bison in order to preclude brucellosis and bovine tuberculosis infection.
IUCN considers around 15.000 bison to be living in the wild. However up to 0.5 million bison live in private areas and 30.000 - in preserves and national parks. They are classified as Near Threatened (NT) with a stable population trend.
Bison was an important component of the flatlands ecosystem in its habitat. When grazing, bison thrust its hooves into the soil, thus fertilizing it. Plains, grazed by bison, were inhabited by prairie dogs, protecting them against predators due to being shorter and thus providing a better view to the surrounding area. Corpses of bison were a delicacy for scavengers while their meat was the main source of food for the local population of wolves and humans. Bison fertilized plains of the habitat thus becoming predecessor of farmers.