Some bears get the idea of territorial expansion and go forth to seize a part of a neighbor's hunting-ground. Thus one bear may be annoyed by another who makes too frequent raids into his domain, and feel called upon to defend his territory against the invader. When past prime a bear is sometimes driven forth into an unfriendly world by a young, vigorous conqueror.
On one occasion I tracked a grizzly for sixty miles from the margin of its home range. It traveled along a line that indicated it had a definite place in mind to which it was going. It explored a cañon region, and, a day or two later, as tracks in the snow showed, went back to its old range along the trail it had followed in leaving it.
Going one autumn from Estes Park to North Park, Colorado, I came upon a grizzly's track in the upper end of Forest Cañon. For several miles it had followed an old wild-life trail. It crossed the Continental Divide, then the No-Summer Mountains. From its trail I judged that it, too, knew where it was going.
Had these bears gone to explore, to see the opportunities of a new region? Or had they returned to old territory which they knew, perhaps to obtain some particular kind of food, or just to have an outing? If seeking new domains, it is possible that they would explore a number of localities before selecting one.
In a few localities bears migrate in the spring and return home in the fall. In these migrations the grizzly breaks his solitary custom and travels in company. Most likely the bears happen to be on the same route at the same time, and, like Pullman passengers, travel together without speaking.
I saw eight grizzly bears one November traveling single file northward from Middle Park. Back-tracking, I found that they had come from the mountainous empire around the southern end of this park. They crossed over into North Park in almost a straight line. Were they, I wondered, heading for a new home, or was this an annual foraging affair? The topography of the country traveled had some bearing on the common route taken, but why were they traveling together? I heard of a number of bears traveling together in northern New Mexico.
On one occasion a hunter on No-Wood Creek in the Big Horns saw seven old grizzlies and two cubs together in the autumn. They were back-tracked to the Yellowstone Park. The garbage-dumps in the Park are frequented by neighboring bears and by numbers from outside the bounds of the Park.