A study argues the number of Yellowstone grizzlies could be in decline and far from the robust status needed to remove the bears from endangered status.
The study, authored by University of Colorado environmental studies professor Daniel Doak, argues that better and more frequent counting of bears in recent years could be misleading everyone about how well grizzly bears are doing in Yellowstone National Park. Alternately, they argue the number of grizzly bears could be static or in design.
In addition, studies of Yellowstone grizzlies populations make one misguided assumption: how often females will breed over the course of 30 years. Doak and crew argue the reproductive rate is lower than what is assumed by researchers. The current official estimate is of 718 Yellowstone grizzlies, up from the approximate tally of 600 reached in recent years. From AP:
Doak said the loss of whitebark pine and a decline in another food source, cutthroat trout, has pushed bears into areas where they are more likely to be seen during aerial surveys done by government agencies. But that doesn’t mean there are more bears.
“It’s a pretty standard thing in all of wildlife biology and conservation biology that if you triple the amount of time you’re looking for some rare species, it’s likely you’re going to seem more of them, just because you spend a lot more time doing so,” he said…
They did not offer an alternative population size, nor say outright that the current estimate was wrong.
One thing that’s important to note when it comes to counting Yellowstone grizzlies: it’s not as though researchers circle the Park in a helicopter and count every grizzly hanging around a hillside. There’s a certain level of extrapolation here, whether it’s an assumption of reproductive rates, an estimate of life expectancy, and the number of bears in a given area. Some researchers have been arguing for years that U.S. Geological Survey numbers overestimate the number of Yellowstone grizzlies; officials say they are striving to be as accurate as possible.
Image courtesy National Park Service.