Caribou Retreat As Development Proceeds

When roads, logging, oil drilling, power lines or even tourist resorts move into caribou range, the sensitive animals move out.

A review of studies from several countries finds that caribou use of habitat declines by 50 to 95 percent within five kilometres of industrial infrastructure.

Research that only looks at a small part of the picture, as did most studies before 1985, doesn't pick up the negative effects of development. Among 36 investigations that were limited to distances of less than two kilometres or periods of less than a day, only four studies found that caribou became stressed from human activity.

More recent broad-scale research refutes the findings of these restricted analyses. Regional studies covering many months or years have overwhelmingly presented a different conclusion. Out of 49 such studies, 41 reported that most caribou avoid human activity and infrastructure development. The results come from research on caribou in Alaska and Canada, and in Finland and Norway where the species is known as reindeer.

Once people start building roads, logging trees or drilling oil wells in the wilderness, caribou vacate the sites, and even suffer reduced birth rates. For instance, after calving grounds in Alaska were overtaken by Milne Point Road and oilfield development, 72 percent of caribou cows eventually abandoned the area for calving, moving to undisturbed habitat. Compared with the caribou that left, females remaining near the oil patch had birth rates that were 10 to 20 percent lower.

In another example, the northward progression of logging in Ontario's boreal forest has coincided with a northward retreat of woodland caribou. The animal's range has contracted permanently. Even after a century of timber harvesting, caribou have not become habituated.

These insights into caribou behaviour are something the Sami reindeer herders of Finland are already well aware of. They know that the best reindeer pastures are those with little disturbance from people. Their semi-domestic animals won't graze properly if conditions aren't peaceful.


Ingunn Vistnes and Christian Nellemann. 2008. The matter of spatial and temporal scales: a review of reindeer and caribou response to human activity. Polar Biology. 31(4): 399-407.

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