by Lynn L. Rogers, PhD -  provided by the Wildlife Research Institute

Black bears sometimes travel great distances.  An example is Big Mac, an 11-year-old male who moved 201 km (126 miles) outside his established range--the farthest ever recorded for a black bear that later returned home.  He left home in late July during a summer when bear foods were scarce due to drought.  He drifted south, then southwest, for six weeks, to an area with abundant acorns.  He settled there for more than a month, foraging mostly by day.

Bob and Terri Hodorff and I wondered what Big Mac bear would do so far from home when it was time to hibernate. Would he spend the energy to return?  If so, would he have to retrace the way he came, or would he somehow know which way was directly home?

Mac began answering those questions on October 15 when other bears were entering dens.  We monitored his activity and could tell from his radio signal that he was resting, not foraging that day.  At nightfall, when he normally would settle down for the night, he began his return trip--moving directly home.  He walked until dawn, barely deviating from a straight line toward home.   For the next eight days, he repeated the pattern, resting by day and moving homeward at night.  He did not depend on stars to navigate, though, because he maintained direction when it was too cloudy and stormy to see them.  He moved like he had a compass in his head, maintaining direction no matter what the obstacles.   He moved through residential neighborhoods undeterred by barking dogs.  He walked across open farm fields, and clambered through jumbled forest, ignoring the paths and logging roads that could have made the journey easier.  They were obviously unfamiliar to him, and they meandered off his homeward bearing. 

His behavior changed when he reached familiar ground a little after midnight on October 24.  He was back where we had radio-tracked him in the years before he made his long trip.  When the sun rose that morning, he continued walking--now moving along forest paths and old logging roads rather than working his way slowly through tangled forest.  A fresh dusting of snow, the first of the fall, showed the details, and it was obvious that he knew where each trail and roadway would take him.   He followed the easy paths even when they meandered off his route.  The trails and road intersections eventually brought him back to his general direction.  A hundred yards before a shaky bridge, which was out of sight around a curve, he left an old logging road and crossed the river on rocks, and then moved back to the road to continue on.  A mile beyond, he left the road, went over a hill, and entered a den that he had never used before.  This little cave had been used by another big male five years earlier, and the den had been empty every year since.  It fit Mac's big body, and he apparently knew that the way he moved directly to it without leaving the paths and roadways to investigate other potential dens along the way.  The cave became his den until the next spring.   

Questions remained:

Why did he move southwest for six weeks without changing direction?  Did the wind tell him that food was in that direction?  If so, how far away can bears detect abundant food crops?

Why did it take him six weeks to walk to the oak area and only nine days to return home?

How did he find his way home?

Do bears carry bits of magnetite in their heads to use as a compass like some other animals do?

Why did he travel only at night when he was moving homeward through unfamiliar territory?  Was he trying to avoid people and resident bears, or could he navigate better at night?

When did he decide to use the cave for his den--before he left on his trip, when he felt the urge to hibernate, or when he arrived home?

Why do bears have such large brains?  Are their navigational abilities superior to those of humans?

How detailed are bears' mental maps of home areas that can be ten miles in diameter in the case of males and that can include vast new areas visited on long excursions?

Would Big Mac return to the area of abundant acorns the next year?  The answer to the last question was revealed the next year when he again wore a radio-collar.  Food was more abundant that year, and he stayed closer to home as he had in years past.  That year, he moved southeast instead of southwest and he moved only 30 miles instead of 126 miles outside his usual range.  Instead of re-visiting the oak area, he moved to a hazelnut area.