Bears Kill a Lot More Prey Than We Thought

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It’s always been the Department of Fish and Game’s intention to remind people that bears are killers, not cuddly stuffed animals, but this study has produced video results that surprised even them.

An article in Science explains that a study aimed to produce a better picture of the brown bear’s day by attaching cameras to several adults. Cameras recorded 10-second clips of video every 10–15 minutes while attached to the necks of brown bears in Alaska’s Nelchina River Basin over the course of three years.

ABOVE: Four grizzly bears were equipped with collar-mounted video cameras in Southcentral Alaska. Each camera took a 10-second video once every 15 minutes, and cameras and video files were retrieved a month later by wildlife biologists with the Alaska Department of Fish and Game. These clips show the bears eating, chasing through brush at a moose calf and grabbing it, rushing at prey, and feeding on another bear.

Not every bear was as prolific with his consumption, but in the average 6.3 percent of their day that the bears spent feeding, they took down calves, hares, and, in one case, another bear. More than 60 percent of their time was spent resting, and another 21 percent was spent in transit.

The study came back with big kill lists, especially during seasons where moose and caribou were giving birth to calves, with bears averaging nearly three times the kills suggested by previous studies. Brockman says there were “several interesting pieces of footage of what the bears ate, including a swan, ptarmigan eggs, and other bears. The most surprising footage was a 10-year-old male brown bear killing and eating a six-year-old female brown bear.”

Bears had previously been thought to kill as little as one calf every nine days. It turns out that, on average, they kill about one a day. One bear managed 44 calf kills in just 25 days.

Of the 17 collared, only seven ended up producing video. Chris Brockman, a wildlife biologist with the Alaska Department of Fish and Game, says this is hard to combat. “The collars need to be tough. The difficulties of fitting cameras on bears is that they are large animals with enough dexterity to pull the collars off if the fit is too loose. Females with cubs have the added difficulty of needing a collar strong enough to withstand being chewed on by their cubs.” So some of the bears (and their cubs) managed to chew off the camera rigs, but the ones that stayed on show bears killing a lot more prey than expected.

With only a handful of bears actually providing data, it’s tough to make the results seem scientific. But painting a portrait of a predator capable of making two kills a day or more is certainly enough to make you rethink the lazy, slumbering image from the zoo, especially if you come across one in the wild.

Still, Brockman has more in mind for further study. “Although what we learned has important ecological implications, the sample size was too small to make large conclusions. I would like to expand the sample size in the Nelchina area so that the results are more broadly applicable to the ecology of that area. After that I would like to start sampling other areas to investigate spatial differences in the diets of bears. I would also like to look at temporal changes in diets. The recently published study only looked at diets in the spring, I would like to continue sampling with cameras in the summer and fall to investigate changes in diets and predatory behavior.”

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