Deaths of female Yellowstone grizzlies on rise

updated 6:12 p.m. ET Nov. 10, 2007

JACKSON, Wyo. - The overall grizzly bear population in the Yellowstone area is thriving, but there is some concern about the number of female grizzlies killed this year.

Interagency Grizzly Bear Study Team leader Chuck Schwartz says the female deaths were approaching a threshold that, if repeated next year, could trigger a review of the decision earlier this year to remove the Yellowstone grizzly from protection under the Endangered Species Act.

There are an estimated 571 grizzly bears in the Yellowstone National Park area.

Of those bears, an estimated 240 are females over 2 years of age, so-called independent-age females.

Researchers estimate that about 18 independent aged female grizzlies have died this year from hunting accidents, management removals and natural causes. That's 7.5 percent of the independent-age female population.

If female mortality exceeds 9 percent of the independent-age female population for two consecutive years, bear management officials from Idaho, Wyoming, Montana, Grand Teton National Park, Yellowstone National Park and the U.S. Fish and Wildlife Service must hold a management review that could put grizzlies back under the protection of the Endangered Species Act.

Wildlife managers say the independent-age females have the biggest impact on the grizzly populations.

Louisa Willcox, director of the Natural Resource Defense Council's wild bears project, said the high mortality among females is just one more reason why grizzlies should remain protected under the federal endangered species law.

"The very first year, just months after delisting, we have a problem," she said.

The Natural Resources Defense Council is one of several conservation groups that have filed a lawsuit against the grizzly delisting.

But Schwartz said one year of high mortality among females does not constitute a crisis.

"We have exceeded sustainable mortality limits in the past," he said. "When we have a year like this, typically the mortality levels drop down again."

In addition, Schwartz said the total grizzly population estimate of 571 bears is likely low.

"As bears increase in this ecosystem, we're likely underestimating what is out there," he said. Statisticians and biologists are working on a new formula for counting the animals.

Further, he said, so far in 2007, research teams documented a near-record 50 females with cubs of the year, with an average litter size of 2.16 cubs.

Schwartz said grizzlies are beginning to den for the winter but are still roaming, leaving the chance for additional female grizzly deaths, particularly during hunting season. Hunters should take precautions, such as removing meat from game animals as soon as possible, to avoid encounters with grizzlies, he said.

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