for National Geographic News
Although the chemical known as deet currently dominates the mosquito-repellent market, nature is full of bug-banishing strategies.
Native Americans once smeared goldenseal root on their bodies to ward off bites. And today candles made with oil from citronella grass help keep the bugs away from backyard barbecues.
Now a team of Australian researchers has isolated one of the most effective natural mosquito repellents yet from an unlikely source: smelly frog skin.
Craig Williams is an ecologist at the University of Adelaide in Australia who led the research team.
"Because frogs have delicate skins designed for absorbing water from their environment, they are vulnerable to things like infections, predators, and [parasites that live in skin]," he said (photos: frogs linked to eco-health).
"So frog skin is really a portable pharmacy" full of chemicals for keeping the amphibians healthy.
Mice in Frogs' Skin
Williams, whose latest findings were published last month in the journal Biology Letters, had suspected for some time that certain frogs emitted substances that protected them from bugs.
"A vast array of compounds had previously been isolated from frog skin: hallucinogens, glues, antimicrobials, and lubricants," he said.
"It made sense that frogs could also develop anti-insect chemicals."
To test this hypothesis, Williams and his colleagues applied low levels of electric current to the skin of five different Australian frog species.
The current caused them to expel larger amounts of their natural secretions than they normally would have.
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