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Keeping Track of Grizzly Bears in the Northern Rockies
Released: 4/27/2010 1:59:06 PM

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USGS uses innovative approaches in bear research

Rural areas with human development can lessen grizzly bear survival in the Greater Yellowstone Ecosystem, and innovative bear rub tree surveys can successfully monitor grizzly population dynamics in the Northern Continental Divide Ecosystem, suggest two new studies released by the U.S. Geological Survey in the Journal of Wildlife Management. 

The studies highlight dynamic tools to assist in conservation and management of grizzly bears in the Greater Yellowstone and Northern Continental Divide ecosystems, the two largest strongholds for grizzly populations in the contiguous United States.

While previous studies identified roads and developed areas as primary hazards, the new findings also indicate that rural home development and areas open to fall ungulate hunting can negatively affect bear survival in the Greater Yellowstone Ecosystem.  Scientists used 21 years of grizzly bear tracking information to develop a model that predicts areas hazardous to grizzlies.

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“Our research shows that bears living in areas with human development and activity including roads, campgrounds, lodges, and homes have a greater chance of dying than bears living in more remote and secure areas,” said Chuck Schwartz, a USGS wildlife biologist and lead of the Interagency Grizzly Bear Study Team.

Additionally, the study indicates that survival of bears over the age of two depends on the level of human development within their home ranges—factors often driven by elevation and road access.  “This type of information is valuable to land managers when planning for resource development, recreational activities, and road building or removal throughout the region,” Schwartz said. 

Another study in the Northern Continental Divide Ecosystem evaluated a method that uses rub tree surveys to monitor threatened grizzly bear populations in northwestern Montana. These surveys may improve insights into bear population dynamics such as growth, decline, distribution, and bear density. 

Bear rubs are anything a bear likes to rub on:  trees, posts, power poles, and cabins.  Scientists mapped bear rubs, collected hair samples, and then used DNA fingerprinting to develop a new way to estimate regional population growth rates.

“These methods could potentially be used for other species that are difficult to study because they live in remote and rugged areas,” said Katherine Kendall, USGS biologist and lead of the Northern Divide Grizzly Bear Program.  “They could also provide a reliable estimate of population trend and be more affordable and safer than collaring bears.”

In 2009, the team began a full scale test to use this method to monitor grizzly bear population trends in the Northern Continental Divide Ecosystem.

The research was conducted at the USGS Northern Rocky Mountain Science Center in collaboration with partners from the University of Montana, Colorado State University, and the U.S. Fish and Wildlife Service.

The article, Hazards Affecting Grizzly Bear Survival in the Greater Yellowstone Ecosystem, was authored by researchers with the USGS and Colorado State University.  The article, Evaluation of bear rub tree surveys to monitor grizzly bear population trends, was authored by researchers with the USGS, University of Montana, and U.S. Fish and Wildlife Service.  Both are published in the May issue of the Journal of Wildlife Management.


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