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December 02, 2008 3:29 am

Grizzly deaths up

Written by Tribune Staff

Population is not down for the count

The grizzly bear population in the Greater Yellowstone Ecosystem has suffered higher deaths this year than in past years, but the population still is growing annually by 4 percent.

According to the Interagency Grizzly Bear Study Team, an estimated 80 grizzlies died in the Greater Yellowstone Ecosystem in 2008. Despite that, the population is on the rise.

In 2007, 49 grizzlies died.

The numbers of grizzly deaths are estimated from known, probable, estimated unknown and unreported deaths from a variety of causes, according to Interagency Grizzly Bear Study Team figures.

In 2007, there were an estimated 571 grizzlies. In 2008, the number increased to 596 grizzlies in the Greater Yellowstone Ecosystem.

Based on those figures, the population will double in 20 years, said Chuck Schwartz, Interagency Grizzly Bear Study Team leader in Bozeman, Mont.

This year's deaths represented a 10.8-percent loss. That is over the 9-percent limit set by the U.S. Fish and Wildlife Service for sustainable growth. That percentage was recommended by the study team.

That may paint a bleak mortality portrait, but, based on Interagency numbers, from 1986 to 2007, the average mortality rate was 4.8 percent.

“One year doesn't make a trend,” Schwartz said.

However, grizzly-bear managers across the region will keep close tabs on population numbers next year to ensure the decline is not a trend, Schwartz said.

“The agencies are on top of it,” Schwartz said.

Scientists and bear managers refer to carrying capacity, or how many animals the land can support.

For the most part, in the 1980s, grizzlies confined themselves to Yellowstone National Park and nearby wilderness areas. By the 1990s, grizzlies had ranged southeast into Wyoming and northwest into Montana. More expansion has occurred since. Now grizzlies occupy lands they were driven out of in the late 1800s and early 1900s, Schwartz said.

But, Schwartz noted that the Greater Yellowstone Ecosystem is a sort of island. There is only so much suitable habitat for expansion.

Once grizzlies venture beyond Yellowstone and the surrounding national forests, they encounter agricultural Idaho lands to the west, and Wyoming agriculture and desert to east.

So it is only a matter of time before Yellowstone Ecosystem reaches carrying capacity.

“Once it's full,” Schwartz said, “that's it.”

Carrying capacity clues include smaller litters, juvenile survival declines and eventual declines in adult survival rates.

Yellowstone Park is already seeing smaller litters and juvenile declines, Schwartz said, and it is only a matter of time before the bear areas beyond Yellowstone's boundaries see similar declines. But at this time, populations are growing inside and outside of the Primary Grizzly Conservation Area.

The Primary Grizzly Conservation Area extends roughly north from Togwotee Pass to Bozeman, Mont., and west of Buffalo Bill Reservoir west to Island Park, Idaho, said Mark Bruscino, Wyoming Game and Fish Department bear management program supervisor in Cody.

Bruscino said this has been a tough year for grizzlies.

This year's crop of white bark pine nuts was dismal. Although this is a preferred high fat and protein food source for grizzlies before they head for winter dens, the bears won't starve or lose weight prior to hibernation, he said.

Grizzlies are experts at re-adapting and finding alternative food sources, such as killing elk and deer or scavenging carcasses or gut piles.

Grizzlies hibernate around the end of November and rise in April, said Tara Hodges, bear-wise community coordinator in Cody for the Wyoming Game and Fish Department.

In March 2007, the U.S. Fish and Wildlife Service removed Yellowstone-area grizzlies from endangered species status.

Before any consideration will be given to placing grizzlies back on the endangered list, the population has to reach 500. Even then, a lot of review and monitoring would follow prior to re-listing, Schwartz said.

But Schwarz noted that conservation groups have a number of suits filed against the U.S. Fish and Wildlife Service. If those lawsuits are successful, grizzly bears in the Greater Yellowstone Ecosystem could return to endangered status.

“That's kind of an unknown,” Schwartz said.