JWM study: Logging may cause caribou stress

Two boreal woodland caribou travel through the snow in Manitoba. ©Dennis Brannen

More than natural events like wildfire, or manmade features like roads and transmission lines, effects of logging operations on their habitat seem to be the biggest indicator of long-term stress for Manitoba’s boreal woodland caribou (Rangifer tarandus caribou).

In a new study published in the Journal of Wildlife Management, researchers originally studying food web interactions between predators and prey used caribou hair samples they had already collected to determine concentrations of the stress-related chemical cortisol.

Comparing hair samples to the home ranges of 55 collared caribou, researchers considered a variety of natural and anthropogenic variables on the landscape and found logging was the strongest predictor of high cortisol levels.

“What was interesting was, we didn’t find fire had much of an influence,” said TWS member James Roth, an associate professor in the Department of Biological Sciences at the University of Manitoba and coauthor on the study. “Fire is the main natural disturbance in boreal forests, but the burned areas in the range of caribou didn’t have an impact.”

Past research had shown that woodland caribou populations appear to be sensitive to logging, Roth said, “but what we were excited about was a physiological indicator of something going on in the environment.”

While cortisol in blood or feces shows short-term responses to immediate stressors, hair samples show longer-term impacts on stress levels, which researchers could match with telemetry data “and see how aspects of their home range affected the animals’ physiology,” he said.

Woodland caribou are threatened through much of their range and their populations are at risk of decline, Roth said, and stress on caribou may also impact predators such as wolves. Researchers don’t know for sure how elevated cortisol levels affect caribous’ reproductive and survival success, Roth said, but research in some captive animals has shown negative effects.

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