Wyoming State Mammal

Bison

(Bison bison)

Adopted on February 23, 1985.

Wyoming's first, and most important, contribution to the bison was Yellowstone National Park, which sheltered the last surviving bison in the United States. Wyoming school children later campaigned for the bison, Bison bison, which beat out the pronghorn and was adopted as the state mammal on February 23, 1985.

Description of the Wyoming State Mammal

They were probably inspired by Wyoming's flag, which depicts a white bison silhouette "branded" with the state seal.

Did you know that: The bison has been proclaimed the official state animal or mammal in each of the following states

State Symbol: Bison

Kansas | Oklahoma | Wyoming

Bison are part of the family Bovidae, to which cattle and goats belong. They are not in the same family that Asian and African buffalo are. However, because they resembled these old world animals, the early explorers called them by that name. Although it is a misnomer, the name buffalo is still used interchangeably with bison. One of the physical differences between the old world buffalo and the American bison is the large shoulder hump of the bison. This hump, along with a broad, massive head, short, thick neck and small hindquarters give the animal its rugged appearance.

Physical Characteristics

The body of the bison is huge, ranging in length from 3.6 m to 3.8 m in males to 2.13 m to 3.18 m in females. They are also tall animals, with the height at the shoulder ranging from 1.67 m to 1.86 m for males and 1.52 m to 1.57 m in females. Two distinctive features of the bisons are the shoulder hump and their huge head. The color of the bison is brown, varying slightly from the front and back of the animal. The hair is longer in the front than in the rear of the bison. The distinction between hair length is more noticeable in males than females. The horns of the bison are black, and they curve upward and inward, ending in a sharp tip. The legs of the bison are short but firm. The hooves are black and are circular in shape (Meagher, 1986).

Food Habits

Bison are year round grazers. They feed primarly on grasses, but when food is scarce, they will eat vegetation such as sagebrush. On the average, bison ingest 1.6% of their body mass per day of dry vegetation. Bison require water every day as well (Meagher, 1986).

Reproduction

Females are sexually mature in two to three years and males reach maturity around age three. Bulls, however, do not breed until six years of age. The breeding season begins in late June and lasts through September. Gestation is around 285 days, so the calving season is from mid-April through May. Any out of season births occur in the late summer. Bison are born in an isolated location that has a lot of cover. Mothers protect the young from danger; males do not participate in this activity. One calf is born per season; the weight ranges from 15 kg to 25 kg. Male calves are born a little more frequently than females. The young calves are red in color. They begin turning brown in two and a half months and are entirely brown in four months. Calves are nursed for seven to eight months and are fully weaned by the end of the first year. Females are seasonally polyestrous with a cycle of approximately three weeks. Estrus may last anywhere from 9 to 28 hours (Meagher, 1986).

Behavior

Bison are gregarious animals and are arranged in groups according to sex, age, season, and habitat. Cow groups are composed of females, males under three years of age, and a few older males. More males enter these groups as the rut approaches. Males live either individually or in groups that may be as large as 30 head. Dominance between the bulls is linear. Bulls that have a higher rank in the society breed more often than those of a lower rank. Cows also live in a linear dominance hierarchy, which is established early in life. Grazing takes place during several periods each day and is conducted in loose groups. When bison travel, they form a line. The traveling pattern of bison is determined by the terrain and habitat condition. An adult cow supplies the leadership. Bison are good swimmers as well as runners, capable of reaching speeds of 62 km/hr.

The olfactory sense of bison is excellent and is essential in detecting danger. Bison can hear very well as well. Bison are able to distinguish large objects from a distance of 1 km and moving objects 2 km away. Bison can communicate vocally through grunts and snorts.

Copulation is initiated by the bull and is quick. During the rut, bulls fight among themselves. The amount of wallowing and tree horning also increases during the rut (Meagher, 1986).

Habitat

Originally, bison were found primarily in and at the fringes of open prairie (Bart, 1957). Now, however, because of their limited numbers, bison are found in many fewer habitats and their movements are very controlled. Within the national parks bison are found at all elevations (Meagher, 1986).

Taxonomic Hierarchy of the Bison