Following the Trail of Stress in Bears

THIS PAST SEPTEMBER, Karl Malcolm scoured the forested mountaintops of Southwestern China for evidence of Asiatic black bears, hiking with a team of Chinese naturalists and an interpreter through rugged, leech-infested terrain. Because of the noise they made, Malcolm didn’t see a single bear, but he did find plenty of the stuff he was looking for: bear poop.

“The locals are always interested to know why someone would come around the world to look for bear feces,” says Malcolm, a doctoral candidate in Tim Van Deelen’s lab in the forest and wildlife ecology department.

But the bears’ waste reveals much about their living conditions and state of mind. Asiatic black bears, also known as “moon bears” for the white crescent mark on their chests, are in decline in China, confined to small nature reserves that are surrounded by—and sometimes cut through with—human development. The bears are stressed, and they leave signs of it in their feces in the form of stress hormones, which Malcolm extracts in hopes of better understanding the landscape factors that aggravate this sensitive species.

There are plenty, to be sure. The forested reserves where the bears live in Sichuan and Yunnan provinces are located at the tops of mountains, rugged places “too steep to till,” explains Malcolm, so they were never cleared for agriculture. Though the reserves contain preferable habitat, they are ringed, like islands, by villages and crop fields that effectively separate bears from potential mates on other reserves.

At night, bears living along the edges of the reserves sometimes descend from the mountains to feast on corn and goats being raised nearby, inciting villagers to retaliate. There’s also an enormous monetary incentive to kill bears. “A single Asiatic black bear, through the sale of its gall bladder, which is a very valuable component in some traditional Chinese medicine treatments, can fetch as much as a year’s salary for a local farmer,” says Malcolm, who has been to China nine times over the past three years for this project, which is run in collaboration with the Smithsonian Institute and Peking University.

By linking data about bears’ stress hormone levels to patterns of human development in and around the nature reserves where they live, Malcolm hopes to generate science-based information that the Chinese government can use to identify and protect key pieces of habitat.

“Ideally, we’ll come away with some concrete information about the landscape requirements for Asiatic black bears,” he says. “And also some lessons about how nature reserves might be managed to best impact the conservation of this and other sensitive species in China.”