View this video on YouTube
Yellowstone National Park Public Affairs Chief Al Nash said the movement of the bison is completely normal and caused by the harsh winters experienced inside the Wyoming park.
The animals migrate from the park during the colder months to seek food at lower elevations, Nash said. When snow melts in the spring, the animals return to the park.
"We have seen no signs to suggest the Yellowstone volcano is about to erupt," Nash concluded.