Stop 6 Managing Bison

Bison were once numerous in Iowa; however, by the 1860s, bison sightings become rare. Today, only captive herds survive in the state. Photo by Rick Hager of a bison in tallgrass prairie.

The American bison or buffalo once roamed great distances across the North American prairies with a population estimated at 30 to 60 million. During the 1800s, European-Americans settled in the Midwest and western regions. Overhunting and habitat destruction reduced the bison population to approximately 1,000 by the early 1900s. 


Beginning in the early 20th century, conservation herds were established to re-build the bison populations which prevented their extinction. In 1996, the Neal Smith NWR bison herd was established and the bison live within the fenced enclosure you are about to enter. As wild animals, they find their own food and water and the herd is managed with minimal interference. 

The herd is maintained at about 55 bison to ensure that they have enough food and to prevent environmental damage within the enclosure. Photo by Joan Van Gorp of a bison herd grazing.

Six national wildlife refuges participate in the USFWS bison genetics program which helps to better conserve and protect their genetic diversity at a national scale. Each animal undergoes genetic testing and receives a microchip implant for identification purposes. 

Each fall, the Neal Smith NWR staff conduct a bison handling operation and the herd is gathered in a facility located within the enclosure. This operation allows staff to assess their health, collect blood samples, and implant microchips into the calves.

Annually, some bison are transferred to prevent overpopulation and inbreeding within the enclosure, and to spread genetic diversity. Genetic factors, sex, and age are used to determine which bison will be transferred to another refuge or other conservation herds. 

Photo by Thomas Dunkerton of a bison having its microchip scanned while it stands in a handling facility chute.
To move bison during the handling operation, staff use low stress techniques, such as hand movements and body placement, which bison respond to instinctively. Photo by Thomas Dunkerton of a bull bison in the chute.
Blood samples are collected during the bison handling operation to document calves’ DNA and to test for disease to assess health of the herd. Photo by Kristie Burns of a staff member preparing bison blood samples.

Now that you have learned about the management of the herd, we hope you get a chance to see them. For your safety, you must stay in your vehicle and remain on the main road as you drive through the enclosure. As you enter, you will drive over a cattle guard which prevents the animals from escaping. The bison are not always visible and you may have to revisit to see them. Good luck on your bison adventure! 

At the refuge, bison calves are typically born during the spring and summer. Photo by Kristie Burns of a cow bison and calf.