A study published last week affirms that what's true for humans may also be true for bears: A junk-food diet and sedentary lifestyle lead to obesity and profound life changes.
A study of black bears in the Sierra Nevada found that those living in urban areas and gorging on garbage weigh as much as 30% more than bears in the wild and are about a third less active. Researchers concluded that they also are less likely to spend time in winter dens, and that they change their sleeping habits to allow for nocturnal dumpster diving.
The study, co-written by Jon P. Beckmann and Joel Berger, is published in the current issue of Journal of Zoology. Beckmann said that, although city bears may be less active than their country cousins, they are not couch potatoes; they simply live closer to their food sources.
"I wouldn't say they are lazy; I would say they are opportunistic," Beckmann said by phone from his research station in Rigby, Idaho. "For bears, garbage is the ultimate resource. It stays in the same place, it's always available and it's replenished after use."
Biologists working for the Wildlife Conservation Society, the research arm of New York's Bronx Zoo, tracked 59 radio-collared bears from 1997 to 2002. In 2001, researchers followed 10 bears living in the backcountry on the edge of the Great Basin near Lake Tahoe -- prime black bear habitat -- and 10 bears that had relocated to towns such as Incline Village.
Researchers for the Wildlife Conservation Society followed the bears and recorded their movements for 24 hours. Food becomes the focal point of bears' lives while they fatten up before hibernation, and black bears consume around 20,000 calories a day during this time, Beckmann said.
Bears in the wild spent more than 13 hours a day roaming the woods foraging for food, researchers found. Bears near the easy pickings of convenience stores and fast-food shops spent only about 8 1/2 hours a day moving about.
The extra body fat on the less active bears means they have little reason to hibernate, Beckmann said. The study concluded that, because the urban bears' food supply is constant, they spend an average of 42 fewer days in winter dens, if any.
Beckmann said that some of the black bears studied were substantially heavier than normal; a few males weighed as much as 600 pounds, more than twice the size of average males.
