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Earth Notes: American Pikas

Dyer Lytle

Hikers in the high mountains of the West have long been charmed by the sight of American pikas peeking out of rocks in talus fields above treeline. 

But scientists are worried that Earth’s warming climate will drive these small mammals higher up the mountainsides—until they basically run out of habitat. In fact, in Zion National Park in southern Utah, pikas were absent from the highest elevations during seven years biologists searched for them.

Pikas, cousins of rabbits and hares, look more like giant mice. They make their homes in chambers under jumbled rocks. These cold-hardy mammals flourished during the ice ages, retreating to the heights as climate warmed.

Their super-charged metabolisms keep their bodies so warm that a rise of only three degrees can be lethal. Pikas will die within a couple of hours when exposed to temperatures in the high 70s.

Yet researchers have discovered that some pikas have found shelter among volcanic rocks in an area that should be too hot for them. They compared sites where pikas have survived to those where they’ve died out, and think a key factor is sufficient cool hours during summer when the animals must gather and store plant foods to carry them through winter.  

Scientist Paul Mathewson and colleagues have created computer simulations that predict there are places in the highest reaches of the Sierra Nevada and Rockies where pikas could survive sheltered among rock piles. These cool microclimates may offer a glimmer of hope for these heat-sensitive mammals.

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