Grizzly bear researchers will conduct genetics testing to determine whether the Greater Yellowstone Ecosystem’s grizzlies interbreed with bears from another region.

Researchers with the U.S. Geological Survey proposed the study at a meeting of the Interagency Grizzly Bear Committee on Wednesday in West Yellowstone, Mont.

Federal judges in Montana and Idaho are currently presiding over three separate lawsuits challenging the U.S. Fish and Wildlife Service’s April decision to remove grizzly bears from the endangered species list. One of the chief arguments against delisting is the population’s lack of genetic diversity, which some say could threaten the health of bears in the ecosystem in the long term.

One or two bears from northwest Montana and Canada must migrate to the Greater Yellowstone Ecosystem and successfully breed each generation for the Yellowstone population to have the appropriate level of genetic diversity, according to a study cited by USGS grizzly bear study team leader Chuck Schwartz.

“We have no documentation of that happening,” Schwartz said.

There is genetic evidence of a hybrid bear in the northern ecosystem, but Schwartz said that bear is likely the offspring of a problem bear that was relocated to Canada years ago.

For the study, researchers will collect genetic samples from all the bears captured or killed in the Greater Yellowstone Ecosystem. Geneticists will then compare the DNA of Yellowstone grizzlies with northern Montana and Canada bears to see if any interbreeding has occurred. If there are no signs of genes from the other ecosystem in Greater Yellowstone bears by 2020, researchers suggested capturing one to two bears from other populations and introducing those bears to the Yellowstone region every 10 years.

Although there is no evidence to date of interbreeding between the two populations, Schwartz said the Greater Yellowstone population is expanding northwest into southern Montana and southeast into Wyoming’s Wind River Range. Researchers say recent evidence from DNA samples and radio collars suggests that Greater Yellowstone grizzlies can disperse at least 140 miles.

One question, according to conservation groups, is whether bears could navigate roads, housing developments and other human disturbances to the landscape between Greater Yellowstone and northwest Montana. Human-caused deaths — especially management removals and hunter accidents — account for the vast majority of grizzly bear deaths. So far in 2008, researchers have documented 36 human-caused grizzly bear deaths, six natural deaths and four deaths that remain undetermined. Researchers say grizzly bears are much more likely to die the closer they get to the outer edges of the ecosystem where there is increased human development.

Franz Camenzind, executive director of the Jackson Hole Conservation Alliance, called the genetic health of the Greater Yellowstone population a “huge concern” because of its isolation and modest numbers. Estimates put the population at close to 600 animals.

“I think it’s long overdue that they start a rigorous genetic diversity study,” he said. 

Camenzind said the states and federal agencies should work to identify and protect wildlife corridors between Yellowstone and northwest Montana. Camenzind also said Wyoming should do more to protect bears in the Wind River Range, which would encourage a larger and therefore more genetically robust Greater Yellowstone population.

“What you need is an expansion of the currently occupied areas,” he said.