American Bison

California Trail

Location

In the Zoo

Scientific Information

Scientific Name: Bison Bison
Class: Mammalia
Order: Cetartiodactyla
Family: Bovidae
Genus: Bison

Size

Male

Female

Height: 6 feet 5 feet
Length: 9 feet 7 feet
Weight: 1800 pounds 1200 pounds
Maturity: 7 years 3 years

Lifestyle and Lifespan

Diet: Herbivorous
Activity Timeframe: Diurnal
Interactivity: Social
Sexual Dimorphism: Yes
Gestation: 270-300 days
Lifespan in the Wild: 25 years
Lifespan in Captivity: 25 years

Geographic Range

United States and Canada, one population bordering the US and Mexico

Conservation

Status in the Wild: Near Threatened
Threats: Over Consumption

Characteristics

This animal is in the same family as cattle, yet it's 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.

Species Specifics

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.

Physical Characteristics

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.

Ecology

Habitat

Grassland, aspen parkland, coniferous forests

Distribution

771 miles for adult females and between 439-660 miles for males.

Diet

Herbivorous; 15-18 lbs. of greens per day. Can meet water requirements by eating snow, but prefer to drink from open water.

Ecological Web

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.

Activity and Behavior

Activity Pattern

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.

Behavior

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.

Social Behavior

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.

Reproductive Behavior

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.

Offspring

1; can weigh up to 66 lbs. at birth and generally are not weaned until they are 8-12 months old.

Conservation

Status

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.

Historical

Original North American range extended from northern Mexico to Alaska. Their population size was estimated at 90 million at their height. By 1900, only a few isolated herds remained in the wild, totaling barely 1,000 animals. The deliberate slaughter was due in part to extirpate native people who relied on bison to make way for ranches and farms.

Current Threats

Over Consumption

Our Role

Oakland Zoo has partnered with the Wildlife Conservation Society in New York and the Blackfeet Indian Nation in Montana to restore a wild herd of American bison to their native territory.

How You Can Help

Vote for the Iinnii Initiative at Oakland Zoo's Quarters for Conservation stations every time you visit the Zoo - pick up your free token when you enter. Learn more about bison and the important role that they play in the prairie environment, and in the history of our country.

Fascinating Facts

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.

References

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. . 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

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9777 Golf Links Road Oakland, CA 94605