Grizzly bears once roamed over about half of the North American continent. In the past 150 years that range has retracted to an area in Alberta and British Columbia to Alaska, the Yukon and a small presence in the Northwest Territories, with other populations in the northwestern portion of US state of Montana, and northern Idaho.
Biologist Scott Neilsen has conducted a 10 year study of Grizzly bears and found that certain conditions such as warmer climate provides a slight benefit to them. He is an assistant professor in Conservation Biology in the Department of Renewable Resources at the University of Alberta.
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In Alberta, the approximate 700 grizzlies left in the province with much of that population found in the rolling foothills and forested edges of the Rocky Mountains.
The bears in the western prairie province are classified as a “threatened” species.
Professor Nielsen says that’s because the bears are particularly sensitive to human activities, the availability of food, and human-bear encounters, which often end badly for the bear. Grizzly bears also have one of the lowest reproduction rates of land mammals, with first reproduction only starting between 5 and 8 years, and bearing cubs only every 3-5 years.
What Professor Nielsen’s study showed was that warmer years benefitted the bears especially mothers by enabling them to forage earlier and build necessary body fat and provide plenty of milk. Cubs born in the warmer springs also tended to grow to larger size through this “silver spoon” effect.
The study also showed that the bears fared better in a mixed forest environment. This meant a range of forest ages from old growth to recently disturbed forests, and associated natural glades and open spaces, each of which provided a different variety of foods for the bears. This “disturbed” forest environment could be caused by natural phenomena like fires, or also by forestry company activity, cutting and replanting, which for a few years gives easier access to food sources.
Professor Nielsen says grizzly health can be determined by body size, and the study showed what environments best suit the bears. “A simple rule is the fatter the bear, the better. Certain environments promote fatter bears”, he says.
His study showed that where a bear is born and when, eg warm springs, resulted in larger adult bears.
While the forest industry may help in certain ways, the activity also has a negative affect with access roads cut through the forest leading to higher mortality rates due to increased human-bear conflict. Sometimes this occurs in the form of vehicle-bear collisions, and potentially enabling easier access for poaching.
It is hoped that the study will help guide forestry management practices, and improve survival rates by de-commissioning access roads.
Professor Nielsen also notes that while, Grizzlies appear to come out alright in terms of climate warming, there will always be winners and losers, and a good example of the latter, are polar bears who are losing the vital ice cover they need to hunt and survive.
The research was funded by Alberta Innovates Bio Solutions, the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation and the Foothills Research Institute.
Applied Ecology Lab ( U Alberta)
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