Human food makes bears hibernate for shorter periods and age faster

A new study published in Nature explored how eating human food, either through foraging through garbage or eating crops meant for human consumption, affects American black bears’ hibernation. The team found that bears who eat human food hibernate for shorter periods, thus accelerating their cellular aging.

Between 2011 and 2015, the research team followed 30 female American black bears in Durango, Colorado, paying close attention to their eating habits and hibernation patterns.

“We quantified relative telomere length, a molecular marker for cellular age, and compared lengths in adult female bears longitudinally sampled over multiple seasons,” study author Heather E. Johnson, from the United States Geological Survey Alaska Science Center, wrote in Nature. “We found that bears that foraged more on human foods hibernated for shorter periods of time. Furthermore, bears that hibernated for shorter periods of time experienced accelerated telomere attrition.”

Johnson also noted that increased consumption of human foods increased bears’ body weights and fertility, as well as reduced their survival rates due to vehicle collisions, lethal management, and other human-related causes. The human foods alone could negatively affect bears’ survival. Some foods meant for humans do not contain species-specific nutritional elements necessary for bears. They may contain toxic compounds or increase the spread of disease.

On top of human-driven climate change, which has already affected the hibernation patterns and fitness of certain animals, urbanized areas where human food can be easily found by wildlife could pose as an “ecological trap” for black bears and other species, Johnson said.

“Our study of a free-ranging large hibernator suggests that increased reliance on human food subsidies reduces hibernation lengths,” Johnson wrote. “Our study also supports previous work on small hibernators that a benefit of hibernation is decelerated telomere attrition. Thus, bears consuming more human foods may lose some of the long-term fitness advantages associated with hibernating, in particular rates of cellular aging.”

“Therefore,” Johnson explained, “the continued growth in food subsidies to wildlife are likely to cascade into altered behavior, ultimately with potential molecular consequences for rates of cellular aging.”

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By Olivia Harvey, Earth.com Staff Writer