February 3, 2010

Climate Change Thinning Out Canadian Wolverines

Conservation scientists say the wolverine, a predator renowned for its strength and tenacious character, may be dying out along with the snowpack upon which it lives, BBC News reported.

Experts say wolverine numbers are falling across North America and their decline has been linked to less snow settling as a result of climate change. It is the first study to show a decline in the abundance of any land species due to vanishing snowpack.

Wolverines typically thrive in boreal forests across Scandinavia, northern Russia, northern China, Mongolia and North America, where it ranges mostly across six provinces of western Canada.

But climate change might be having an impact on snowpack levels, and on the animals that depend on it, according to Wildlife biologist Dr. Jedediah Brodie of the University of Montana, in Missoula.

Brodie and his colleague, Professor Eric Post of Pennsylvania State University, gathered data on snowpack levels across six provinces of Canada: Alberta, British Columbia, Manitoba, the Northwest Territories, Saskatchewan and the Yukon Territory.

They found that snowpack depth declined significantly between 1968 and 2004 everywhere but in the Yukon.

Brodie told the BBC it occurred to him that a good first place to look for ecological impacts of that snowpack decline would be with a snow-adapted species like the wolverine.

The researchers examined the records of wolverine numbers caught by fur trappers over the same period of time and found a striking correlation between declining snowpack and falling numbers of the predator.

"In provinces where winter snowpack levels are declining fastest, wolverine populations tend to be declining most rapidly. Spring snowpack also appears to influence wolverine population dynamics," the researchers said.

The Northwest Territories were the only province where wolverine numbers are increasing, as snowpack levels there are declining but remain much higher and less variable than in most other provinces.

Brodie said recent studies show that wolverines appear to use areas with deep snowpack for dispersal.

"So reduced snowpack could make dispersal more difficult or dangerous, potentially reducing the success rate with which individuals can establish new home ranges," he says.

"Reduced snowpack may also make it harder for wolverines to get food, for several reasons. First, harsh winters and deep snow are major causes of mortality for ungulates like elk, moose, deer and caribou. If milder winters mean that fewer of these animals die over the course of the winter, then there will be fewer carcasses for wolverines to feed on," he explained.

He said wolverines also hunt rodents, and that food source may be important for wolverine reproductive success in some areas. But shallower snowpack is bad for a lot of rodents because it provides less insulation from the cold, he added.

"So if declining snowpack reduces rodent abundance, that could be bad for wolverines," said Brodie.

He said his study is the first to show a decline in species abundance due to a reducing snowpack - for any land animal, not just those in North America. But he says there are interesting parallels in marine systems.

He said one example is that sea ice is critical for polar bear foraging, as polar bear body condition, reproductive rates, and survival have declined significantly in Hudson Bay as sea ice breaks up earlier in the spring.

Brodie also pointed out that Antarctic sea ice has increased over recent decades, which may have negative impacts on adelie penguin populations that depend on ice-free areas for breeding and foraging.

"As climate change worsens, we should reduce trapping levels and also disturbance to boreal forest habitats. Reducing the impact of these anthropogenic stressors could help 'offset' the impacts of climate change on wolverines," said Brodie.


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