Hibernating Animals Face Less Extinction Risk

Feb. 19, 2009 -- A spell of bad weather might send you running to bed. Plenty of animals act the same way, and it turns out the reclusive behavior can be a remarkably good way to avoid extinction.

Mammals that regularly hunker down, hibernate, or otherwise hide from the world are better at weathering environmental change than are less hermitic species, according to a new study. The finding offers a window into which animals might thrive as the climate changes and habitats vanish.

"Just imagine yourself in a war zone," said lead researcher Lee Hsiang Liow, a paleobiologist at the University of Oslo. "Having some food storage and a place to avoid harsh environmental conditions would help you survive that period while there was bombing outside in your habitat."

Liow and colleagues from both the University of Oslo and the University of Helsinki were originally looking in the fossil record for a link between body size and extinction rates among mammals.

An unexpected outcome of the study, published last year in the Proceedings of the National Academy of Sciences, was the hint that hibernation-like behaviors, which are more common in smaller animals, might help explain why smaller animals tend to be better survivors.

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To test the idea, the scientists tapped into a database of more than 4,500 living mammal species. For most species, they looked at nine so-called sleep-or-hide behaviors -- including hibernation, using burrows or tunnels, and going into a state of torpor or dormancy. Next, the team looked up each species' category of conservation, as listed by the International Union for Conservation of Nature (IUCN).

The analyses, published this month in the American Naturalist, found that having at least one sleep-or-hide behavior made a species less likely to appear on the IUCN Red List as threatened or endangered. The category included black bears, hedgehogs, and raccoon dogs native to Asia.

The scientists used statistics to account for body size and range size -- both are strong predictors of an animal's risk of extinction. And still, the findings held.