The American Bison is the largest land mammal native to the Western Hemisphere, and a leading icon of the American west. Bison served as the foundation to many Native American tribes, whose lives were synced to their migrations and wholly dependent upon their meat and hides. Interestingly, the bison is not a true buffalo - that distinction is held by the Cape Buffalo of Africa and Water Buffalo of Asia. The word buffalo in America has been used colloquially for so long that it's now interchangeable with bison.
Range and Population: Before European settlement and westward expansion, bison numbered 20-30 million across the Great Plains from Canada to New Mexico. Numbers declined nominally when Native Americans acquired horses in the 1600s and could hunt more effectively, but still never to excess. Unregulated hunting by settlers on an unprecedented scale - in addition to US Army initiatives aimed at reducing populations in order to weaken Native American tribes - drove numbers down to an estimated 1,090 by 1889. Restoration efforts, led by public and private interests, have lifted the population to approximately 500,000 across North America. Most are not 'pure' bison, however, as many have been cross-bred with domestic cattle. Yellowstone National Park has the largest population of free-roaming plains bison (2,000 - 4,500), and is one of only a few herds with cattle-free genes. The majority of today's bison live on private ranches and are managed as livestock (approximately 400,000).
Physical Traits; Adult bison stand 5 - 6.5 at the shoulder, are 10-12' long, and weigh 900-2100 lbs. Females are about half the size of males and sport narrower horns, a smaller hump, and smoother summer coats. Bison can live 12-20 years in the wild, and over 30 in captivity or managed herds. Bison are North America's largest ungulate, or hoofed animal. They're also ruminates, which means they regurgitate food and chew it as cud -a secondary form of mechanical digestion that breaks down fibrous grasses and shrubs. Bison have poor eyesight, but acute hearing and smell. Bison appear can run 35 mph and are surprisingly nimble over short distances.
Bison Horns: They grow heavy, curved horns that can reach nearly two feet. Horns are a formidable defense against predators, and used in mating battles between males (injuries are rare). Males are distinguished from females by their larger size, more triangular head, and broader shoulders. The female's horns are typically more slender and curved. Behavior Bison live in herds that move continuously over long distances to avoid overgrazing.
Bison herds left such indelible marks on the land that their tracks - a reliable indication of passable terrain - were often followed by Native Americans and European pioneers. A hierarchy of females (cows) generally lead family groups, while males (bulls) distance themselves in small bachelor herds. The two come together in very large herds during the height of summer for the mating season, which peaks July-August. During this time males agitate easily, and its best to keep a very respectful distance. Bison are well known for wallowing, a process of rolling and rubbing themselves into the ground that forms a distinct depression stripped of vegetation. Wallowing helps remove molted fur and combats external irritants like insects. Males wallow energetically during mating season to exhibit strength and virility.
Reproduction: Bison herds come together by mid-summer and mate by early September. Males battle aggressively to form small harems, though injuries are rare. Males guard females in estrous jealously; once complete, the polygamous male moves on to another. Females give birth to one calf after a nine month gestation, typically mid-April through May. Calves have a distinct red-rust color for the first 30-60 days of their lives. Mothers are very defensive, and can become aggressive if threatened. Calves can run with the herd just hours after birth, and are well-guarded by the mother and herd. Bison become sexually mature at age 2, though males typically must wait several years to breed. Wolves and grizzlies pose the greatest natural threat to bison, but predation is limited and serves to strengthen the herd by weeding out weaker animals.