Photo courtesy WCS
North America’s urban areas have become death traps for black bears, luring wild populations to a diet of garbage and an early demise, the Wildlife Conservation Society reported today.
“Black bears that live around urban areas weigh more, get pregnant at a younger age, and are more likely to die violent deaths,” WCS said in conjunction with a study published in the Fall 2008 issue of the journal Human-Wildlife Conflicts.
The New York-based charity tracked 12 bears over 10 years living in urban areas around Lake Tahoe, Nevada and compared them to 10 bears living in outlying wild areas.
The bears in urbanized areas weighed an average of 30 percent more than bears in wild areas due to a diet heavily supplemented by garbage. The researchers believe that because the bears weigh more they are giving birth at an earlier age — on average when they are between 4-5 years old, as compared to 7-8 years for bears in wild areas. Some urban bears even reproduced as early as 2-3 years of age around Lake Tahoe.
Urban bears also tend to die much younger due mostly to collisions with vehicles, the investigation found. “All 12 urban bears tracked by the researcher were dead by age 10 due to vehicle collisions, while six of the wildland bears still survived,” the Society said. Bear cubs in urban areas also had dramatically higher mortality rates due mainly to vehicle collisions.
File photo by George F. Mobley/NGS
“Urban areas are becoming the ultimate bear traps,” said WCS researcher Jon Beckmann, the study’s lead author. “Because of an abundant food source — namely garbage — bears are being drawn in from backcountry areas into urbanized landscapes where they meet their demise.”
Urbanized areas are “sinks” for black bear populations, drawing in bears from outlying wild areas, where they ultimately die, the study warns. As a result, bears are failing to re-colonize outlying wild areas following this shift to urban centers.
WCS believes that without these sinks, populations of black bears in Nevada could increase. Right now, populations in Nevada remain steady due to bears immigrating from neighboring California.
The Wildlife Conservation Society is studying the effects of urbanization and sprawl on a variety of wildlife and habitats in North America.