Researcher Licks Poison Frogs in Pursuit of Science

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Valerie Clark has a quick way to determine whether a frog is toxic or not. She licks them.

If it is not dangerous it is certainly nasty. “I don’t recommend this,” Clark told National Geographic News earlier this year. “If you lick the wrong frog it can be very bad.” (Read the story.)

Clark studies frog chemical defenses. She earned her master’s degree at Columbia University in New York City, and has received funding from National Geographic to do research on the ecology and evolution of chemical defense in the poison frogs of Madagascar.

Watch a video and read more about Valerie Clark’s research in the extended entry.


Using what she calls the “quick-lick taste test,” Clark swabs her tongue along the back of Madagascar’s Mantella poison frog, an amphibian mildly toxic to humans.

If it tastes bitter then it’s probably a poison frog.

“But not all poison frogs are distasteful,” the herpetologist says.

“Some populations of poison frogs have little or no taste or burning sensation effects. My recent National Geographic expedition to Madagascar revealed some adaptations of certain populations of poison frogs that appeared, by taste tests, to have lost their toxic cocktail, becoming edible to predators. I’ll be reporting details on the adaptations of palatable poison frogs in coming months.”

Tasting frogs like this in the field saves having to carry chemically boring specimens back to the laboratory for more conventional testing, Clark explained the last time she was at National Geographic headquarters.


Not all poison frogs can be tasted like this. The skin of the golden dart frog of South America is so toxic it could kill the human that tried to taste it. “It is always best to do a quick safety sniff first,” Clark says. “Some poison frogs exude a a bit of chemical that burns the throat.”

Clark admits that on one occasion licking a poison frog resulted in a a swollen throat and difficulty swallowing for a day or so. “The orange treefrog was called the taboo frog by the [Guyana] locals, but I was too curious,” Clark says by way of explaining why she went ahead and tasted the frog anyway.

Poison frogs obtain the toxins in their skin from their diet. Clark’s research focuses on trying to find out which of the insects the Mantella eats could be passing the toxins on to the frogs. Understanding that helps establish more about the frog’s habitat and the importance of protecting that habitat’s diversity. The chemistry of the frog could also be important for human medicine.

We posted this National Geographic Wild Chronicles video about Clark’s work in Madagascar earlier this week:

Valerie Clark plans to continue studies of frog secretions for her PhD and future academic career. National Geographic Magazine features her in the November 2008 issue, and no doubt we will be blogging and reporting about her again.

Changing Planet

Meet the Author
More than forty years in U.S., UK, and South African media gives David Max Braun global perspective and experience across multiple storytelling platforms. His coverage of science, nature, politics, and technology has been published/broadcast by the BBC, CNN, NPR, AP, UPI, National Geographic, TechWeb, De Telegraaf, Travel World, and Argus South African Newspapers. He has published two books and won several journalism awards. In his 22-year career at National Geographic he was VP and editor in chief of National Geographic Digital Media, and the founding editor of the National Geographic Society blog, hosting a global discussion on issues resonating with the Society's mission and initiatives. He also directed the Society side of the Fulbright-National Geographic Digital Storytelling Fellowship, awarded to Americans seeking the opportunity to spend nine months abroad, engaging local communities and sharing stories from the field with a global audience. A regular expert on National Geographic Expeditions, David also lectures on storytelling for impact. He has 120,000 followers on social media: Facebook  Twitter  LinkedIn