GPS Tracking Shows That Black Bears Avoid Humans During the Day

A pair of researchers analyzed GPS tracking data from American black bears (Ursus americanus) to see how their movements vary depending on the season and time of day.  Black bears start hibernating during the fall, a period where the bears will lose up to a third of their body weight.  To prep for this long period, black bears will engage in hyperphagia, the consumption of 15,000 – 20,000 calories per day.  Human sources of high calories, such as food tossed away into trash cans, pet food left out, and bird seed, attract bears into developed areas.  At the same time, black bears have a fear of humans.  Researchers wanted to track the geographic movements of black bears to see what adaptions these animals might be making in the tradeoff between access to food and avoiding dangers presented by humans.

Black bear foraging in a trash can. Photo: Florida Fish and Wildlife, 2008, CC BY-ND

Black bear foraging in a trash can. Photo: Florida Fish and Wildlife, 2008, CC BY-ND

To track the movements of the bears, researchers  looked at GPS collars data obtained between 2009 and 2017 from 86 black bears in Massachusetts.  The pattern of their movements would reveal the risk-reward trade-off these large mammals engage in.  Comparative studies on black bear movements in areas remote from human interference has shown that these bears tend to prefer to move during daylight and crepuscular hours than at night.  The researchers analyzed the movements of bears from the GPS tracking data and found that, in alignment with other studies that looked at black bear behavior in developed areas, the bears had altered the timing of their foraging movements to occur at night when the risk of human interaction was lower.  This study also aligns with other studies that have found a growing trend of animals adjusting their daily movements to become more nocturnal to avoid humans.


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The Study on Black Bear Movements

Zeller, K. A., Wattles, D. W., Conlee, L., & DeStefano, S. (2019). Black bears alter movements in response to anthropogenic features with time of day and season. Movement Ecology, 7(1), 19. https://doi.org/10.1186/s40462-019-0166-4

Black bears adapt to life near humans by burning the midnight oil.  (2019).  Zeller, K.A.  The Conversation.

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