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Two-fold Increase Reported in Grizzly Bear Deaths in Greater Yellowstone Ecosystem

A spike in the mortality rate for grizzly bears has been reported in the Greater Yellowstone Ecosystem earlier in the season than is typical according to my colleague Frank van Manen. Dr. van Manen is the Team Leader of the Interagency Grizzly Bear Study Team and President of the International Association for Bear Research & Management.

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Formed in 1973, to address specific concerns over the management of grizzly bears in the Greater Yellowstone Ecosystem (GYE), the Interagency Grizzly Bear Study Team monitors the status and population trends of grizzly bears in the region.

Essentially, the Team conducts research that will determine whether GYE grizzlies will retain “threatened” status under the Endangered Species Act.

Substantial changes in demographic and population trends in the GYE grizzly bears could influence policy and ultimately conservation status, which makes this report more of a significant finding.

Under the auspices of the Department of Interior, the Team is comprised of scientists representing the U.S. Geological Survey, National Park Service, U.S. Fish and Wildlife Service, U.S. Forest Service, the Eastern Shoshone and Northern Arapaho Tribal Fish and Game Department, and the States of Idaho, Montana, and Wyoming.

Although most deaths in the region at this time of season are usually human-caused, 10 of 16 grizzly bears monitored by the Team died of natural causes already this year.

In an interview with Dr. van Manen, journalist Mike Koshmrl noted the following:

Although the data may warrant attention, biologists refrain from jumping to conclusions and caution others to do the same. “We should be careful not to make too much of this,” said Frank van Manen. “We’re seeing the typical range of conditions that we’d see with grizzly mortality.

“The fact that there were two females with cubs that were killed inflates the numbers a little bit,” van Manen said. “We’re seeing an aging of the population as well. It wouldn’t surprise me if we start to see more of these bears dying from old age.”

Concern over the declining population of whitebark pine stands due to mountain pine beetle infestations has been speculated as potential factor in the deaths of the bears.  Whitebark pine tree seeds are an important pre-hibernation food source for grizzlies in the region.

But they are a critical late-season food source for grizzlies, not an earlier-season resource. So according to van Manen it is “probably too early to say” if the conifer plays a role in the mortality rate recorded thus far this season. In fact, seed production seemed “pretty reasonable” compared to productivity in the past few years, according to the bear biologist.

It remains to be seen what impact this mortality rate will have on the population of bears in the GYE, which numbers around 600 animals.