Northern brown bears discovered feeding on whitefish runs

September 22nd, 2009 in Biology / Ecology

The discovery of brown (grizzly) bears feeding on migrating broad whitefish in a stream in Mackenzie Delta region of the Northwest Territories has researchers advising increased care in petroleum extraction and infrastructure development within the area.

In a paper published in the September issue of the journal Arctic, Oliver Barker and Andrew Derocher from the University of Alberta report seeing at least one brown bear engaged in the unusual activity of caching whitefish at Pete's Creek, a small Mackenzie River tributary located between Inuvik and Tuktoyaktuk. While it is well known that brown bears feed on salmon, trout and charr, this is the first scientific reporting of brown bears feeding on whitefish and supports what is recorded from local traditional knowledge.

Each spring since 2003, several bears were outfitted with satellite radio-collars. In October 2007, while conducting a helicopter survey of the bears, the researchers noticed two patches of disturbed ground near Pete's Creek. What they found when they landed surprised them - two caches with whole and partially eaten whitefish.

"My first impression was excitement. My second was apprehension," says Barker, "I don't like being in willow thickets when there are bears nearby."

Realizing their shotgun was in the helicopter, Barker beat a hasty retreat. Once in the air, they did indeed observe a young female nearby. "She was quite fat and shiny. Very roly-poly,'" recalls Barker.

Brown bears in the Mackenzie Delta face several challenges. Not only are food sources scarce, the bears are often active for just five months of the year. This creates extreme pressure for them to find adequate nutrition.

"These bears are real opportunists. They'll take advantage of different food sources," says Barker. This means some will turn to whitefish which are easily available in large numbers when they migrate in the fall. And although bears are omnivores and can exist on mostly vegetarian diets, fish are a better food source because they are rich in protein and fat.

Barker says the fall run of whitefish could be playing a significant role in the diets of some Mackenzie Delta brown bears. He would like to see more research conducted on the bears and their feeding habits, in order to mitigate the impacts of development activities.

"Pete's Creek may be an important but spatially concentrated food source, but we can't put it into context until we know more" says Barker. "It could take a small amount of disturbance in an area like this to disrupt these bears. There is still a lot we don't know about Mackenzie Delta bears, and any development should be mindful of such resources."

Source: Institute of North America

"Northern brown bears discovered feeding on whitefish runs." September 22nd, 2009. http://phys.org/news172842131.html