Bearly surviving

0 Comments | Insight on the News, May 27, 1996 | by Dan Whipple

Conservationists hope genetic research will ensure the future of the endangered grizzly bear.

Genetics may hold the answers to two of the most pressing matters concerning the long-term survival of the American grizzly bear: population size and genetic diversity. Researchers already have achieved provocative results about the evolution of bears and the genetic makeup of ursine populations worldwide.

In the early 1800s, 50,000 to 100,000 grizzly bears ranged over North America west of the Mississippi River. By 1900, only small, scattered populations remained. The U.S. Fish and Wildlife Service listed the grizzly as a threatened species in 1975, estimating that fewer than 1,000 bears remained in a few pockets of Yellowstone National Park and along the Canadian border.

Biologists are concerned that Yellowstone grizzlies, which live in an ecological island, may not have enough genetic diversity to survive in the long run. As fewer bears are squeezed into a shrinking habitat, inbreeding may affect their health and fertility.

But large carnivores are notoriously difficult to count in the wild. Independent researchers Steve and Marilynn French have undertaken a three-year study in Yellowstone using baits and scents to attract grizzlies and collect hair samples from which they can determine the genetic makeup of individual bears. The group also will analyze samples of grizzly-bear hair taken from specimens in museums to create a DNA profile of the bear population 100 years ago, before the range of the bear was dramatically reduced. "The question is, have we made a difference in the last hundred years by isolating them in this geographic island?" says Steve French, a medical doctor who practices in Evanston, Wyo.

Oxford University geneticist Ryk Ward, who is working with the Frenches on the project, has pinpointed 30 "microsatelhtes" -- sequences along the DNA strand -- that will allow him and his colleagues to catalog specific characteristics about each bear, determine kinship and probe into genetic diversity, the concrete pillar underlying conservation biology.

In an effort to vary the gene pool, wildlife managers have proposed a series of protected corridors through forestland that would connect the Yellowstone grizzlies with bear populations further north. This idea, a favorite of conservationists, would dramatically increase the amount of acreage devoted to bear recovery in an area already under pressure from developers interested in its rich mineral resources, recreation potential and real-estate value.

But the proposal is unlikely to be embraced. "Nobody in the bear world believes that [corridors] work," says Steve French. "The bears aren't going to travel 240 miles from point A to point B. They never have. Bears tend to migrate outward in concentric circles." Expanding the protected area around Yellowstone outward in ever-widening concentric circles has even slimmer prospects.

A second, more palatable solution to declining genetic diversity might be to bring in other bears to augment the existing population in Yellowstone. The Frenches' work can determine which bears still extant in the lower 48 states are the best matches to the Yellowstone population and target those for introduction into the ecosystem.

In the long run, however, the recovery of the grizzly bear rests on habitat management. "Most of this habitat will be managed by man forever," says French. "There will always be pressure for multiple use. Molecular genetics will allow us to monitor how effectively we're managing the habitat."