Frogs cool off, then warm up to survive

Sept. 29, 2011 at 8:18 PM
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DARWIN, Australia, Sept. 29 (UPI) -- Australian green tree frogs survive the continent's dry season by using the same phenomenon that makes eyeglasses fog up in the winter, researchers say.

Researchers from Charles Darwin University found tree frogs would often lay outside on cool nights during the dry season in tropical Australia and then return to their dens, where condensation would form on their cold skin, just as it does on a pair of glasses when someone comes in from the cold.

The frogs can absorb the moisture directly through their skin, and hydrated during periods of little or no rain, researchers said in the study published in The American Naturalist.

"Every once in a while, we would find frogs sitting on a stick under the open sky, on nights when it was so cold they could barely move," research leader Chris Tracy said. "It was a real puzzle."

The researchers set out to see whether the frogs could collect enough moisture through condensation to compensate for what they lost being in the cold.

They found that a cold night out cost a frog as much as .07 grams of water -- but it could gain nearly .4 grams, or nearly 1 percent of its total body weight, in water upon returning to the warm den.

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