From: Andy Soos, ENN
Published April 28, 2010 03:48 PM

Tracking Grizzly Bears

Keeping track of where wildlife may wander may give important keys on how they live and prosper as well as how to maintain their lifestyle. Rural areas with human development can lessen grizzly bear survival, 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 grizzly bear (Ursus arctos horribilis)is a subspecies of brown bear (Ursus arctos) that generally lives in the uplands of western North America Yellowstone, Rocky Mountains). This subspecies is thought to descend from Ussuri brown bears which crossed to Alaska from Eastern Russia 100,000 years ago, though they did not move south until 13,000 years ago. Grizzly bears are found in Asia, Europe and North America, giving them one of the widest ranges compared to other bear species.

Grizzlies are normally solitary active animals, but in coastal areas the grizzly congregates alongside streams, lakes, rivers, and ponds during the salmon spawn. Although grizzlies are considered carnivores, they are actually omnivores, since their diet consists of both plants and animals. They will also scavenge when necessary.

The USGS studies highlight new dynamic tools to assist in the 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 to the bear population, the new findings also indicate that rural home development and areas open to fall deer 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 potentially hazardous to grizzlies.

“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(where humans want to go or to live).  “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.

Now what is a "rub"? 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. This method is distinctly non-intrusive for the bear.

“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.”

Collaring bears refers to the practice of putting a collar (about one pound in weight) on a bear's throat. The collar transmit a signal that can be recorded remotely and then plotted to show where the bear goes in its habitat and how often. This method is minimally intrusive for the bear being studied.

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

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