Chris Geremia

As biologist Chris Geremia will explain in a Thursday talk, bison change the way spring happens across Yellowstone National Park’s vast grasslands. Without several thousands of bison moving freely on the landscape in sync, the springtime season of plant growth would be shorter, the land would not be as green, and the plants would not be as nutritious. On a typical June day in Yellowstone, it’s not unusual to see thousands of bison grazing in the Lamar Valley. The groups appear aimlessly roaming back and forth. But as it turns out, that’s far from the full picture.

Geremia will offer a more complete overview of the animals’ impact on Yellowstone during a Draper Natural History Museum Lunchtime Expedition titled, “Migrating Bison Engineer a Better Yellowstone.” The program, hosted on Zoom by the Buffalo Bill Center of the West, begins at noon Thursday. To register for the virtual talk, visit www.bit.ly/3rfae0e.

Bison return to graze the same areas repeatedly at such intensity that it turns back the clock on forage green-up, hitting reset on springtime. Their grazing sets bison apart from other ungulates and allows them to time their spring migrations differently from other species. Moreover, their grazing directly alters nutrient cycles, plant growth potential, and the very makeup of plant communities. We are learning that in the same way predators can influence the Yellowstone ecosystem from the top down, bison can push on it from the bottom up. Put another way, the influence of bison on plant communities in the park is as natural and important to the ecosystem as those of top predators like wolves.

Geremia is the lead bison biologist in Yellowstone National Park. His team is responsible for conserving bison within the park, studying bison demography, genetics, and their role in engineering grassland ecosystems. The team also works to reduce conflicts that occur when bison migrate out of the park. He recently led his team in establishing a transfer program that has returned live Yellowstone bison to Native American tribes as an alternative to slaughter. 

Geremia has worked as a member of the Bison Program in Yellowstone since 2001, earning his PhD in ecology from Colorado State University in 2014.