LIKE a canary in a coal mine, a small mammal native to the American West is warning about climate change. And the news isn’t good. The most comprehensive survey of the guinea-pig-like pika in 50 years suggests that rising temperatures might make trouble for some small animals sooner than anyone expected.
“This is one of the first examples of a mammal showing widespread response to climate change,” says ecologist Erik Beever of the US Geological Survey in Corvallis, Oregon. “We tended to assume that these things happen over centuries or millennia, but my study suggests these populations are dying out in just decades.”
American pikas (Ochotona princeps) die quickly if their body temperature rises only a degree or two above normal. Normally, pikas move in and out of sunlight and rocky shelter to regulate body temperature.
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Their sensitivity to climate stops them from straying too far from home, so sub-populations have developed in isolated pockets in the mountains of Nevada and eastern Oregon. Most scientists have long believed that’s where they’ve stayed, more or less unchanged, since a heatwave drove them there 11,000 years ago.
To confirm that, Beever checked 25 sites where pikas have been spotted during the past 75 years. Each was expected to contain up to 50 pikas. Over several years, he traced only 18 of the 25 populations. His results will appear in the February 2003 edition of the Journal of Mammalogy.
“This rate of extinctions is surprisingly high,” says University of Washington archaeologist Donald Grayson, who specialises in studying animal extinctions.
Beever used computer models to test 21 combinations of seven possible explanations for the pika’s demise, including loss of habitat, isolation from other pika populations, human disturbance and temperature change. Climate change consistently turned out to be one of the top three factors.
Grayson says the climate effect is striking, but cautions that all animals are different. “If we are going to understand the impacts of global warming on mammals, it has to be done one species at a time,” Grayson says. “Tell Erik to do marmots next.”