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Greater Yellowstone’s grizzly population is large and continues to grow, and more bears could die each year without hurting the population, some members of a grizzly management group said in Jackson last week.

The comments came from members of the Yellowstone Grizzly Coordinating Committee less than a year after the number of dead female bears exceeded the group’s own limits. A grizzly team leader said he has “no doubt” that the current model underestimates  the number of bears and that managers “could probably allow for more [deaths] of females without affecting the population.”

The comments came from Chuck Schwartz, leader of the U.S. Geological Survey Interagency Grizzly Bear Study Team, the parent group under which the Yellowstone committee operates. Conservationists who oppose raising death limits contested his statements, saying the grizzly remains threatened by humans and deteriorating food sources like whitebark pine trees.

A principal issue is that the 30 female bears killed by humans in 2008 exceeded the limit of 22 set by federal and state agencies.

“I’m a little puzzled as to how we can be exceeding the mortality limit, have a population drop, and they think it’s a good idea to raise the mortality limit.” said Craig Kenworthy, conservation director of the Greater Yellowstone Coalition.

Schwartz acknowledged the potential controversy of increasing the allowable annual death count.

“There are some people who will accuse us of moving the goal posts,” he said. “That’s not true. There is science behind this.”

Some committee members argued in favor of increasing the adult female “mortality threshold,” the percentage of bears that researchers think could die in the ecosystem without causing a decline in the population. Exceeding the female mortality limit two years in a row triggers a management review of the species.

While bears were recently under state management, that review could have put them back under federal Endangered Species Act protection. Meantime, a federal judge agreed they need that federal oversight anyway.

Wyoming Game and Fish bear management supervisor Mark Bruscino said he isn’t worried about the current level of mortality in the ecosystem.

“I think it’s sustainable,” Bruscino said. In the future, he said, high levels of mortality might be the norm because bears continue to move into areas where people won’t tolerate them.

The discussion comes one year after roughly 30 of 251, or nearly 12 percent, of adult female grizzlies in the region died, exceeding the mortality threshold of 9 percent. The estimated total Greater Yellowstone population subsequently dropped from 595 bears in 2008 to 579 this year.

From his office in Montana, Schwartz said the 9 percent threshold was a conservative measure designed to keep the grizzly population either stable or growing. Now that grizzlies have mostly filled the available habitat in Greater Yellowstone, he said the need to maintain an expanding population is diminished.

“Our current rate of growth in Greater Yellowstone is probably 4 or 5 percent,” he said. “Our rate of reproduction is greater than our rate of mortality.”

Now that Greater Yellowstone is beginning to fill, bears have started moving out into areas where they are not accepted by humans, Schwartz said. Grizzlies that live in the secure habitat in Greater Yellowstone should act as a source population, an area that provides dispersing grizzlies to the surrounding areas with higher mortality, he said.

“I honestly believe that the long-term success for conserving grizzly bears in the ecosystem is linked to human acceptance of bears,” he said. “We can’t allow bears to try to live in places where they don’t belong.

“Managing for a population that continues to increase doesn’t make sense,” Schwartz continued. “Where are you going to put all those excess bears? Subadult bears are going to continue to disperse. That’s when you get bears lining up in places where bears don’t belong – in places with high human density. People won’t tolerate it.”

Schwartz said the mortality could likely grow to 11 percent without a decline in the population. Before that threshold is changed, he said the proposal would have to go through a rigorous review that includes a scientific study, peer review and a public comment period.

“I’m not recommending that [the mortality thresholds] be changed,” he said. “It’s the managers who are asking that we evaluate the thresholds, so they might consider changing them.”

Louisa Willcox, senior wildlife advocate for the Natural Resources Defense Council, said wildlife managers need to be cautious as they consider changing the annual quota of dead females.

“Breaching your own mortality thresholds should give one pause about what is going on in the population,” she said of last year’s numbers.

There are several reasons why the grizzly bear population could be leveling out that have nothing to do with the Greater Yellowstone Ecosystem habitat filling up with bears, Willcox said. Those include a loss of whitebark pine and increased mortalities due to conflicts.

The current mortality limit isn’t antiquated, added the Greater Yellowstone Coalition’s Kenworthy.

“They did this science fairly recently and set that limit and said this is what it ought to be,” he said. The ecosystem isn’t full of grizzly bears, he said.

“It would be way too early to declare that they’ve filled those niches,” he said. “I think we need to have conversations about what those niches should be from a biological and social standpoint.”

Schwartz is also working on the science behind a proposal that would modify the rules that wildlife managers and biologists use to estimate the size of the grizzly population. The current model is based on counts of female grizzlies with cubs of the year. To make sure the same bears aren’t counted twice, there are rules based on the distance between sightings, descriptions of the family group, and the dates of the sightings.

For instance, scientists currently say the minimum distance required for two groups of grizzlies to be counted as distinct is a diameter of 30 kilometers. But Schwartz said a distance of 10 kilometers might be a more accurate way to count.

“We’re simply looking at the science that is used to make these estimations,” he said. “It’s up to the managers to decide to what degree they’re going to implement the science.”