Female Bears Care for Their Young Longer to Escape Hunters

Brown bears have learned to protect themselves from hunters by caring for their young for longer periods, thus adapting to the law that prohibits hunting ‘bear families’.

A group of international scientists spent 22 years studying data on the reproductive strategy and survival of Scandinavian brown bears. The results were published in the journal Nature Communications.

– Humans have become an evolutionary factor in the lives of bears, says Professor Jon Swenson from the Norwegian University of Life Sciences (NMBU).

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In Sweden, the bear hunting season is long, and no special hunting license is required for it, with about three hundred bears being shot each year. However, female bears with young are protected by law.

– A female bear without young has four times the chance of being killed compared to one with a cub, said Swenson, one of the study’s authors.

Scientists realized that some female bears have adjusted their maternal approach to improve their chances of surviving hunting, effectively using the bear equivalent of a shell shield. In the last 20 years, female bears have extended their care for their young from an average of one and a half years to two and a half years.

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– As long as the female has young around her, she is safe. The pressure of hunting has resulted in a change in the length of care for offspring, which has increased from 1.5 years to 2.5 years, the study states.

Between 2005 and 2015, the number of female bears that kept their young around for an additional year increased from seven to 36 percent.

– This is the first study that convincingly suggests a change in the frequency of maternal strategy driven by hunting, said Swenson.

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Bears are not the only species whose evolutionary change has been forced by human behavior, says lead author of the study Joanie van de Walle told AFP.

– We have documented evolutionary shortening of horns in American bighorn sheep in Alberta, Canada. This happened because trophy hunters favored those with the longest horns. Those with shorter horns are not as interesting to them, so they have a better chance of surviving, she said.