Yellowstone bison: Why are bison being removed from the population?

Bison in Yellowstone National Park. Credit:
Bison in Yellowstone National Park. Credit:

From the National Park Service

Why are bison being removed from the population?

  • Bison populations increase rapidly when environmental conditions are suitable. Yellowstone bison are prolific and have high survival rates, with wolves currently killing few bison because elk are more vulnerable prey. We’re not aware of any bison conservation herds in North America that are naturally regulated: all require population reduction through hunting or culling.
  • Bison need to be removed from the population at times. The fast-growing bison population could fill available habitat and out-pace the acquisition of additional habitat and tolerance for bison in Montana. Options for relocating Yellowstone bison elsewhere are limited by real and perceived disease and social concerns.
  • Under-nutrition (starvation) only contributes to high mortality when bison abundance is high and snow pack is at or above average. Also, most bison migrate to lower elevation areas in response to such severe weather events —which eventually brings them into conflict with agriculture and development.
  • The food-limited carrying capacity inside the park could be as high as 5,500 to 7,500 bison during winter, but lower-elevation habitat for bison is limited by mountains in the park and by competition with agriculture, development, and transportation systems outside the park.
  • A panel of expert scientists reviewing Yellowstone bison and brucellosis issues concluded that culling or removals of bison, along with hunting, would be necessary to limit the size of the bison population for biological, social, and political reasons.