YELLOWSTONE NATIONAL PARK, WY - SEPTEMBER 24, 2014: A bison grazes on grasses in the Hayden Valley section of Yellowstone National Park in Wyoming. (Photo by Robert Alexander/Getty Images)
YELLOWSTONE NATIONAL PARK, WY - SEPTEMBER 24, 2014: A bison grazes on grasses in the Hayden Valley section of Yellowstone National Park in Wyoming. (Photo by Robert Alexander/Getty Images)