Lifestyle and Lifespan
This animal is in the same family as cattle, yet its appearance sets it apart. Bison are the largest terrestrial mammals in the western hemisphere. Large bodied, wide triangular head, with brown hooves with a hunchback appearance and horns are signature characteristics of this species.
American Bison are divided into two subspecies, plains bison (B. b. bison) and woods bison (B. b. athabascae) that are inhabitants of the woodlands of northern Canada and Alaska. Plains bison are smaller and lighter in color than the woods bison.
Bison are usually slow moving, but can run up to speeds of 37 mph when chased. They have a strong sense of smell (aiding in predator detection) and can hear and see well. They are also strong swimmers. Bison are better able to maximize nutrition in areas with poor forage and have lower cholesterol, fat, and calories in their meat than cattle.
Grassland, aspen parkland, coniferous forests
771 miles for adult females and between 439-660 miles for males.
Herbivorous; 15-18 lbs. of greens per day. Can meet water requirements by eating snow, but prefer to drink from open water.
Where bison have been studied, grazed areas have a 36-85% higher production of grass than ungrazed areas, partly stimulated by the high mineral content of bison feces and urine, which contain 90% of the phosphorus and 65-95% of the nitrogen from ingested foods. Predators: Gray wolves, grizzly bears and humans.
Bison graze for 9-11 hours each day, resting, ruminating, or moving for the remainder. They generally stay in one area for several days then travel several miles to a new area. They can move during the night or day. They migrate with changing seasons; winter foraging areas occur more often in sheltered meadows and in riparian zones. Most herds today can no longer make long migrations due to fences.
During storms, they will face into the wind and rain and endure them. Regardless of age and sex, they roll in dust baths and mud wallows which help protect their skin against mud and help dislodge old fur. They will also rub on trees, boulders, and other objects to dislodge old fur.
Herd sizes are generally 20-60 animals and communicate via vocalizations and posture, including tail placement. Older bulls can move alone or can form bachelor herds. Males will exhibit threat displays and fight year round; most frequently before and during rut. Females will threaten and charge when protecting their calves. A study in Alberta found that 73% of threat displays did not get physical. If bison do fight, males can collide at full gallop and wrestle with horns locked. Horns can break ribs and puncture organs.
Females go into estrus about every 3 weeks for only 9-28 hours. Males exhibit the flehmen response, tasting the female's urine to establish if she is in estrus.
1; can weigh up to 66 lbs. at birth and generally are not weaned until they are 8-12 months old.
Listed as Near Threatened by the IUCN; One subspecies (B. b. athabascae) listed in Appendix II of CITES and Threatened under Endangered Species Act. Population Trend: Stable, Current herds occupy less than 1% of their historic range.The total number of mature individuals in wild free-ranging and semi-free-ranging populations is estimated to be approximately 11,250 and most bison are on private lands.
American Bison, also known as American Buffalo, once roamed the grasslands of North American in large herds. They are the largest land animal on the continent weighing between 1000-2000 lbs. in males and 800-1200 lbs. in females. Bison were nearly wiped out in American history. In the 19th century Westward expansion, Bison neared extinction due to slaughter and bovine diseases from domestic cattle. They declined from 30-60 million free ranging to around 1000 in 1906. A small original heritage wild herd was taken to Canada and remained established at Elk Island Park. Crossbreeding with cattle (thought to create healthier meat and more resilient animals) has increased the population, but has also polluted most remaining wild herds of bison, and increased exposure to deadly cattle diseases. Habitat loss also results in little space for Bison to develop large, genetically diverse herds. Today there are around 500,000 bison on private lands and 30,000 on public lands, but only about 15,000 are considered wild, free-range bison not primarily confined by fencing. Current herds occupy only 1% of their historic range. The Northern Tribes Buffalo Treaty was signed in 2014 to enable partnership to restore wild buffalo to the plains. President Obama signed the National Bison Legacy Act into law in 2016, making the American bison the national mammal of the United States.
Iinnii Initiative: Oakland Zoo partners with WCS and the Iinnii Initiative in Montana to restore a wild herd of American bison to their native territory. The zoo will raise young bison for yearly release in Montana – in the care of Blackfeet Nation people. This will add genetic diversity to the heritage herd and bring back a culture that will enhance the wellbeing of these people and the nature around them. Education, Eco-Travel and Cultural Exchange: CSC is developing eco-travel programs to Montana to study bison with the Blackfeet Nation Communities, an Economic Benefit program to sell Blackfeet Nation artisan goods at our gift shop, production of BF Nation Bison ceremonies and an annual National Bison Day in November, and creation of a Teen Cultural Exchange with OZ and Blackfeet Nation youth. Zoos and Parks: Oakland Zoo is working with the ZPP, the Zoo Parks Partnership that will enhance our relationship with Glacier National Park and ultimately benefit bison and all animal in this shared habitat. Our partnership will be a model for other zoos and parks.
Often incorrectly called buffalo; both buffalo species are also in the Bovidae family, but both African buffalo and Asian water buffalo are in different genus than bison.
Traditionally, American bison were split into two subspecies, the Wood and Plains bison. However recent evidence suggests that environmental factors can account for the differences in coat between the two subspecies, and genetic data from their mitochondrial DNA suggests they should not be divided.
Evidence taken by some biologists may indicate American bison and European bison are actually the same species and should be placed in the genus Bos, not Bison. European bison are listed as endangered currently by the IUCN.
Our female bison are part of the Iinnii Initiative heritage group. They started at Elk Island and were brought to Montana in 2016 along with others, then came to Oakland Zoo in April, 2018. Many of the bison to our surprise arrived pregnant, and have given birth to 10 baby bison! In May 2019 seven females and their calves (11 total) were sent back to the Blackfeet Nation in Montana to the free-ranging herd. In July 2019 two males were added to our Oakland Zoo herd from Colorado State University. The males were produced using non-surgical embryonic transfer techniques from the Yellowstone Park genetic pool.
Convention on International Trade in Endangered Species of Wild Fauna and Flora Appendices I, II, and III. (2012). Retrieved April 12, 2012 from http://www.cites.org/eng/app/appendices.php
Jdeidi, T., Masseti, M., Nader, I., de Smet, K., & Cuzin, F. 2010. Canis lupus. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 03 June 2012.
Elbroch, M & Rinehart, K. Peterson Reference Guides: Behavior of North American Mammals. 2011.
Larter, N. & Cormack Gates, C. Home Range Size of Wood Bison: Effects of Age, Sex, & Forage Availability