Andrés Ordiz

Alpha predators like bears, wolves and mountain lions are used to calling the shots in nature. But when humans arrive with guns and hounds, this hierarchy is displaced in more ways than one. Obviously, hunting costs animal lives, but some researchers also speculate that a hunter’s presence reverberates in other ways, too, changing the behavior of these large carnivorous quarry. In other words, predators know they’re being hunted.

For example, “it’s been argued for some years that in Europe, wolves and brown bears are more nocturnal than in North America as a consequence of a long history of human persecution,” said Andrés Ordiz, a conservation ecologist at the Norwegian University of Life Sciences and the lead author of a paper for the journal Biological Conservation that investigates the phenomenon.

In Europe, animals have been adapting to human predators for about 40,000 years, the study explains; North American wildlife are thought to have begun adapting to human hunters around 5,000 years ago. The researchers specifically wondered how large carnivores like bears might be influenced by the presence of today’s gun-toting humans.

To answer this question, Dr. Ordiz and colleagues tracked the movements of 78 brown bears in Sweden with GPS-equipped collars from 2003 to 2010. A handful of the females had cubs during the study period, while the rest lived solitary lives.



In their study area, the bear hunting season begins in late August and usually continues for a month or two, after the year’s quota of 45 to 75 bears is met. During this hunting window, Sweden’s 3,300 brown bears are busy eating as many berries and nuts as possible in preparation for the 5 to 7 months they spend hibernating throughout the winter.

Usually, the bears forage for about 12 hours a day, taking a midday nap and also sleeping during the darkest hours of the night. The researchers expected that, as winter approached and the Scandinavian nights grew longer, the bears would start focusing their foraging efforts during daylight hours.

They followed their subjects for two weeks prior to the start of the hunting season and two weeks after the hunters were unleashed. To their surprise, as soon as the first hunting party hit the scene, the bears drastically changed their patterns of activity.

Rather than taking advantage of the limited daylight hours, they chose instead to operate mostly during the darkest periods of the night. They also increased the distance they traveled to find food, especially after midnight, a period when bears usually slept prior to the hunting season.

“Probably through many years of hunting, bears have learned that people in the forest with dogs are a danger,” Dr. Ordiz said. “They’re definitely more nocturnal than before, and the most likely reason is that they’re avoiding contact with people.”

These findings only applied to solitary bears, however. The handful of females with cubs continued to forage throughout the day in spite of the hunters’ presence. (Incidentally, it is against the law to shoot females with cubs in Sweden.) But solitary females without cubs were just as deeply affected by the presence of hunters as the male bears.

Dr. Ordiz speculates that females tending to their young may not be able to afford to stop feeding them during the day, or that maybe that they are foraging in denser areas of the forest where hunters are less likely to venture. More data need to be collected before those distinctions can be teased out, though.

Now that the researchers know the bears are changing their behaviors in response to hunters, the next step is figuring out what costs, if any, these changes have on their ability to thrive. Past research, for example, has shown a clear relationship between female bears’ adeptness at fattening up during the summer and their success in producing cubs the following spring.

If hunting influenced solitary females’ ability to gain enough weight to rear cubs, it could have a significant impact on bear populations.

The researchers suggested that future conservation and management discussions include ways to mitigate behavioral impacts of hunters on bears, especially if their hunch proves true that hunters are influencing the reproduction or survival of some animals.

Dr. Ordiz said the results might apply to other large carnivores as well, although other studies would be needed to confirm that.

“Our findings are signs of a preliminary warning, in a way,” he said.