These cleared paths, she concluded, made it easier for the bison to move around within the park and, on occasion, led them on mass migrations out of the park as well. Life is 50-50. It's what you take in, that's the calories, but the other half, especially in a harsh environment like this, is the energy it costs. Energy saving is really crucial in this environment. The next year they had moved another quarter of a mile further west.
Animals learn too.
But not everyone reached the same conclusion. In 1997 Dan Bjornlie, then a graduate student in ecology at Montana State University, also set out to determine exactly how and why the bison had migrated. They recorded where the animals were and if they were feeding, traveling or resting. The group came up with some surprising results, which put many traditional ideas about bison behavior in question. For the most part, the animals had not moved from these neighborhoods.