BOULDER, Colo., March 11 (UPI) -- The grizzly bear, on the edge of extinction in the lower 48 states just 25 years ago, is recolonizing its habitat south of Yellowstone National Park for the first time in a hundred years, a study has found.
The study, by Denver Zoo biologist Sanjay Pyare and several other bear biologists, concluded southern expansion from Yellowstone by grizzlies now is doubling every 20 years.
In the early 1980s, a study of the grizzly population in the greater Yellowstone area found fewer than 200 bears, and projected that the bear could be extinct by the 2000. Instead, the Interagency Grizzly Bear Study Team estimated there now are a minimum of 500 bears in the ecosystem -- probably more -- and the population is healthy and expanding at the rate of about 4 percent per year.
"It is a tremendous success story," Steve Thomas, the Sierra Club's regional director of the Northern Plains region, told United Press International.
Thomas added, however, the area designated as the "core habitat" for the bear should be increased before wildlife officials consider removing the animal from the Endangered Species List. The U.S. Fish and Wildlife Service is expected to propose removing the bear from the list by the end of this year.
"The health of the bear population is getting better and better, we agree with that," Thomas said, "but that is mostly because of the protections offered by the Endangered Species Act ... We don't think the core conservation area is adequate. It needs another 3 million acres, including the southern part of the ecosystem. That is better habitat in some ways than the Yellowstone Plateau."
The biologists' study, which was published in the January issue of Animal Conservation, the journal of the Zoological Society of London, reported the grizzly bear has reoccupied about 50 percent of the southern Greater Yellowstone ecosystem.
"Based on assumptions of continued protection and ecological stasis, our model suggest total occupancy in 25 years," the study concluded. "Alternatively, extrapolation of linear expansion rates from the period prior to protection suggest total occupancy could take (more than) 100 years."
Not everyone in the path of this expansion is thrilled about the idea. About two years ago, the county commissioners of Fremont County, Wyo. -- along the eastern front of the Wind River Mountains to the south of the park, but within the Yellowstone ecosystem -- passed a resolution that prohibits the presence of grizzlies, gray wolves and other "unacceptable species" in the county. How the resolution was to be enforced was not specified. The commissioners also banned the food storage regulations the U.S. Forest Service had instituted to keep grizzlies out of local garbage cans.
Bears love garbage, but it poses one of the biggest threats to their survival.
"The biggest single factor in the grizzly's continued health is conflict with humans," Chuck Schwartz, leader of the Interagency Grizzly Bear Study Team, told UPI. "Bears are attracted to developed sites by garbage, dog food, bird food, pet food and they end up dying because of it."
Once a bear has lost its fear of humans, virtually the only solution for wildlife managers is to kill it, Schwartz said.
He said he gives much credit for the bear's recovery to the changes in garbage handling in Yellowstone and the surrounding communities -- Livingston and West Yellowstone, Mont., and Jackson, Wyo. -- for the improvements in the bear's population numbers.
"Garbage in Yellowstone is now picked up every day," Schwartz said.
Another factor that will determine the grizzly's future is the fate of the private lands in the GYE.
"Taking what used to be a cattle ranch and slicing and dicing it into ranchettes or high density subdivisions takes what was good grizzly habitat and makes it unsuitable," Schwartz said.
A major question for the future is "how do we keep them from wandering from less-developed into high-density areas, getting people to live with the grizzlies?" Schwartz asked. "Bears are a lot more accepting of humans than humans are of grizzlies."
Dan Whipple covers the environment for UPI Science News. E-mail email@example.com