American Bison

Bison bison
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The American bison, also commonly called buffalo, once numbered in the millions, and the nomadic herds roamed great distances across the North American prairies. During the 19th century when the great plains were being settled, their populations were decimated. Beginning in the early 20th century, conservation herds were established to re-build the populations and prevent extinction. Neal Smith National Wildlife Refuge (NWR) manages one of these conservation herds today, usually numbering 70-90 animals. They live in a 700-acre enclosure, and can be seen from your vehicle on the auto tour route, from the trails and visitor center.

At Neal Smith NWR, the bison are being managed for genetic diversity. Each animal has had hair and blood samples taken to determine its genetic make-up, and has been marked with a microchip so we can identify an individual animal. This genetic information is used to protect the genetic diversity of our herd and the other herds managed by the U.S. Fish & Wildlife Service across the country. When our herd grows too large for the enclosure, bison that have rare genes are kept in the herd and bison with only common genes may be sent to other herds. We also consider age and sex when deciding which animals to keep. We try to maintain an even ration of males to females and of individuals from each age group. The bison at Neal Smith NWR do not have any detectable cattle genes, although they may be present; it’s impossible to know for sure because the entire genome has not been mapped. If cattle genes are present, there are so few that they do not affect the behavior of the bison.

Each fall, refuge staff round up the entire bison herd to assess their health, collect hair from calves and put a microchip in the calves. As the bison enter the health screening facility, each animal is scanned, weighed, and their body condition is assessed by a biologist. As they are scanned, a computer displays where each bison is to go: directly back onto the prairie, into the chute for disease testing, or into a pen for removal from the herd. New calves are all tested for genetics and injected with a microchip. Typically, bison that are to be removed are yearlings and two-year-olds.

Why do we need bison on the prairie?

Bison play a very important role in the prairie ecosystem. Bison are attracted to areas that have been recently burned, where the fresh green sprouts of new plants provide protein-rich food. As large bison herds move into an area, they eat most of the plants in that area. This impact on plant height provides habitat for wildlife that prefer shorter plants, including some birds and insects. Grazing stimulates the growth of some plant types, making them grow more to provide more food. By favoring grasses in their grazing, the bison provide more opportunities for wildflowers to grow with less competition from the tall grasses.

Bison also create wallows, which are bare dirt depressions, by rolling on the ground to get rid of biting insects and hair when they are shedding, and to cool off when it’s hot. Bulls also wallow to leave their scent and display their strength. Large wallows collect water during rainfall, creating habitat for amphibians and aquatic insects. Some types of plants and invertebrates also like the soil disturbance found around wallows.

Another way bison shape the prairie is by moving seeds from one place to another. As bison roam around, they carry seeds with them both in their stomachs and in their hair. This helps plants move throughout the prairie ecosystem, and sometimes provides them with fertilizer to help them sprout. Currently, new research about the impact of bison on seed transportation is going on at Neal Smith NWR. Visitors may see university researchers collecting data inside the enclosure.

Facts About American Bison

Bison are grazers – they eat plants

Adult bison are over 6 feet tall and can weigh up to 2,000 pounds

Bison can run up to 35-40 mph for short distances