Urban Life for Bears: Short and Violent

11/01/2008 05:12 am ET | Updated May 25, 2011
  • Andrew C. Revkin Dot Earth

The human species is now a mainly urban animal for the first time in history, according to the United Nations, and in at least some regions of the United States, black bears appear to be following suit. One new study tracking bear patterns for a decade around Lake Tahoe, Nev., finds that urbanized human settlements are a lure and a threat to the opportunistic omnivores -- attracting bears with abundant garbage, but killing many in collisions with vehicles. The study tracked 12 female bears frequenting the town since 1997 and compared their condition and fate to 10 females in undeveloped wooded areas.

Bears in developed areas, gorging on garbage, typically weighed 30 percent more than bears in wild areas. The authors of the study, published in the fall issue of the journal Human-Wildlife Conflicts, concluded that the extra weight caused urban females to reproduce about three years earlier than their counterparts in the wild. But high mortality more than offset any population gains from earlier reproduction.