Humans stressing out skittish caribou

U. WASHINGTON (US) — Human activity, including oil production and the timber industry, not overzealous wolves, are the primary cause for the dwindling caribou population in Alberta, Canada.

The caribou population has been declining in the region for several decades causing speculation that the entire population could be gone in 70 years. Further, in the area of the petroleum-rich Athabasca Oil Sands in the northern part of the Canadian province, some researchers predict they could disappear in as little as 30 years.

While the drop in caribou in recent decades is certain, populations have held relatively steady in the last four years, says Samuel Wasser, conservation biologist at the University of Washington.

In a new study, published in the journal Frontiers in Ecology and the Environment, Wasser calls for controlling the impact of human activities before resorting to more drastic actions such as removing wolves from the area.

Northern Alberta’s oil sands deposits are second only to Saudi Arabia as a potential petroleum source. The Athabasca deposit is the largest of three that cover about 54,000 square miles.

In 2005, North American Oil Sands Corp. was interested in determining what was happening to caribou, moose, and wolf populations in the Athabasca Oil Sands region south of the city of Fort McMurray, where the company held oil leases.

In 2007 the company was acquired by Norway-based Statoil, which continued to fund the research that focused on whether the caribou population decline resulted from habitat changes because of roads and other infrastructure associated with the oil and forestry industries, from physiological stress caused by human activity, or from excessive wolf predation brought on by increased numbers of deer and, consequently, wolves.

The oil sands are in an area covered largely by forests and peat bogs, and most human activity takes place from mid-December to mid-March, when the otherwise marshy ground is frozen and ice roads can be used.

Scat samples from caribou, moose, and wolves, well preserved because of sub-freezing temperatures, were collected in the winters of 2006, 2007, and 2009. In 2009, four teams of highly trained scat-detection dogs led to the recovery of 2,000 samples of caribou, moose, and wolf scat in 10 weeks.

In examining the samples, researchers determined habitat preferences for each species, their abundance, the type and quality of food consumed, and hormone levels that could indicate whether the animals were under psychological or nutritional stress, or both.

Deer were found to make up 80 percent of wolves’ diet, with caribou and moose each accounting for about 10 percent.

Moose favored habitat associated with food and didn’t seem particularly concerned about people. The result was that their scat had low levels of stress hormones and high levels of nutrition hormones.

But caribou proved to be much more skittish. They chose open, flat areas where, presumably, they could see and hear predators and escape. That also made it easier for them to see and hear humans on the landscape. Their scat reflected high stress and low nutrition in areas nearer roads when humans were most active.

It turned out that wolves mostly favored areas inhabited by their favorite food source, deer, which also is habitat with few caribou.

Removing wolves could actually have unintentional consequences, Wasser says, because with a much-reduced wolf population, the number of deer would probably increase rapidly. The deer could alter the habitat and perhaps reduce the caribou food supply. Deer also carry multiple diseases that could jump to the caribou population.

Until there is evidence to the contrary, changing human activity patterns is safer, he says.

The research also produced the first precise numbers of the caribou, moose and wolf populations in this wooded habitat. As of 2009, the scientists estimated 330 caribou, 387 moose and 113 wolves within the small section of oil sands included in the study. The caribou population was more than double the highest previous estimate.

None of the populations changed significantly during the four years of the study.

The work provides options that can help reduce impacts from human development. For example, instead of roads or pipelines being routed in a straight line on open, flat terrain, they could wind through more complex wooded terrain and avoid areas that caribou prefer for food and security.

The tools developed to evaluate scat samples for evidence of habitat selection, population changes, nutrition and stress will also provide the means to tell quickly whether mitigation efforts are working or if changes are needed, Wasser says.

“They would be able to make course corrections quickly and effectively.”

Researchers from the University of Alberta and Montana State University contributed to the study.

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