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American Bison

Updated: Mar 8, 2021

by Abbie Krause

America's National Mammal

Few things are as symbolic of the story of the American West as the American Bison. Its majestic physical presence, importance as a keystone species and its comeback story led Congress to honor this iconic and resilient species, with the 2016 National Bison Legacy Act designating the American bison as the National Mammal. During this current pandemic and politically challenging times, it is inspiring to remind ourselves that this designation was made citing that the bison is ”a U.S. symbol of unity, resilience and healthy landscapes and communities.” What more appropriate and needed inspiration could Americans ask for during these challenging times? Indeed, when things could not look bleaker for the American bison at the turn of the last century as it teetered on the edge of extinction, their comeback story and the recognition of the historical, cultural, and economic importance of bison can serve as a reminder to all of us of some core centering values and provide hope. The logo says it all.

The Pueblo Zoo is proud to be home to three bison and has adopted the Laramie Foothills Conservation Herd as one of their four priority conservation species. The bison of the Laramie Foothills Conservation Herd are descendants of the Yellowstone National Park herd, notable for its valuable and unique genetics. Yellowstone National Park is the only place in the U.S. where bison have continuously lived since prehistoric times. What makes Yellowstone’s bison so special is that they’re the pure descendants (free of cattle genes) of early bison that roamed our country’s grasslands. The problem has been that the Yellowstone herd also carries brucellosis, a devastating disease to cattle that has been eradicated elsewhere in the United States. This partnership of Colorado State University, USDA, County of Larimer and the City of Ft. Collins is key in preserving the genetics of pure bison.

The Pueblo Zoo is proud to be able to contribute to that effort not only through contributions to the conservation organization, but also in a practical, hands-on way as the home of bison that will hopefully contribute to the population of genetically pure bison.

In 2017 CSU contacted the Pueblo Zoo for help with two young calves that had been abandoned by their mothers. Pueblo had a three-time bison mother who also rejected her calves giving the zoo keepers extensive experience in hand-raising calves. Sid and Ginger came to Pueblo and thrived. Testing confirmed that the dominant bull in Pueblo, Cody, had pure bison genetics untainted by cattle genes. The hope is that Cody and Ginger will breed and one day contribute to the population of pure, disease free bison.

FACT BOX by Anne Casey

American Bison

Scientific name: Bison bison

Common name: American bison, Plains bison, American buffalo (though they are technically not true buffalo)

Description: Bison are recognized by the large hump over their shoulders and their sharply-pointed, two foot long, curved horns. The head, neck, forelegs, and the front part of the body are covered in long, dark brown hair, while the rear part of the body has shorter, lighter hair. They shed this coat in spring. Males also have a black curly beard about one foot long. The bison is the largest terrestrial animal in North America – bulls can be 5.5 to 6.5 feet high at their hump and 9 to 12 feet long. Females are somewhat smaller, only 5 feet high and 7 to 10 feet long. They weigh in anywhere from 930 pounds for cows to 2200 pounds for bulls, typically.

Range: Once widespread from Canada to Mexico, bison are now restricted to just one percent of their native range. Conservation herds are found in many parts of Canada and in the western United States, including California, Alaska and all the western states from the Dakotas south to Texas.

Habitat: Bison once covered the Great Plains from Mexico to Canada. They prefer grasslands, but can also be found in open, grassy forests, shrublands, and deserts.

Behavior: Bison are grazers, preferring to eat grass, though they will switch to forbs and tree leaves, bark, and lichen when necessary. Their large heads are used like snowplows in the winter to find the grass beneath the snow. In their original native range, some herds were migratory, moving to find food and water with the seasons. They live in groups, or bands, arranged by sex, age, season, and habitat. Older bulls are solitary, while cows and their young, including immature bulls form their own bands, as do mature bulls. These bands come together in the spring and fall to form large herds. Bison graze during the morning and late afternoon, resting while they chew their cud in the middle of the day. Bison wallow in the dust and mud to keep biting insects at bay.

Reproduction and rearing: Females mature at 2 to 3 years and males reach maturity at 3 years, though they do not usually breed until they are 6 years old. Mating occurs between June and September. Gestation lasts 285 days. Calves are born singly and have a lighter coat color. They are able to follow the herd after a couple of days. They will nurse for 7 to 8 months and are completely weaned by the end of one year.

Predators: A mature bison does not need to worry about predators, but the calves and older or injured bison can fall prey to wolves, mountain lions, and bears.

Lifespan: Bison live to 15 to 20 years.

Conservation Status: Though the bison once numbered in the tens of millions, now the IUCN Redlist lists Bison bison as Near Threatened due to habitat loss, hybridization with domestic cattle, and low genetic diversity.


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