Bison in Lamar Valley - Yellowstone National Park
Yellowstone preserves the most important bison herd in the United States. Yellowstone is the only place in the United States where bison (Bison bison) have lived continuously since prehistoric times. Yellowstone bison are exceptional because they comprise the nation’s largest bison population on public land. Unlike most other herds, this population has thousands of individuals that are allowed to roam relatively freely over the expansive landscape of Yellowstone National Park and some nearby areas of Montana. They also exhibit wild behavior like their ancient ancestors, congregating during the breeding season to compete for mates, as well as migration and exploration that result in the use of new habitat areas. These behaviors have enabled the successful restoration of a population that was on the brink of extinction just over a century ago.
Bison are the largest land-dwelling mammal in North America. Males (2,000 lbs/900 kg) are larger than females (1,100 lbs/500 kg) and both are generally dark chocolate-brown in color, with long hair on their forelegs, head, and shoulders, but short, dense hair (1 in/3 cm) on their flanks and hindquarters. Calves of the year are born after 9 to 9-½ months of gestation. They are reddish-tan at birth and begin turning brown after 2-½ months. Both sexes have relatively short horns that curve upward, with male’s averaging slightly longer than those of adult females.
All bison have a protruding shoulder hump. Large shoulder and neck muscles allow bison to swing their heads from side-to-side to clear snow from foraging patches, unlike other ungulates that scrape snow away with their front feet. Bison are agile, strong swimmers, and can run 35 miles per hour (55 kph). They can jump over objects about 5 feet (1.5 m) high and have excellent hearing, vision, and sense of smell.
