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Audio Finds Frog Counters May Be Overestimating

Frog census volunteers misinterpreted recorded frog sounds in the field, leading researchers to suspect that frog populations may be even lower than thought. Cynthia Graber reports

Declining frog populations are considered an indicator of environmental damage. But new research finds that frogs might be doing even worse than we thought. Because the volunteers who count frogs by their sounds may be overestimating.

The North American Amphibian Monitoring Program is the country’s largest frog-counting system. Volunteers listen for frogs, identify the species, and give population estimates. They’ve been doing this for over a decade.

Ted Simons from North Carolina State University and colleagues put recordings of frogs, like this wood frog, [Wood Frog sound] in the field to test the volunteers. They call it Ribbit Radio.

Many volunteers ended up with false positives—they named frog species whose calls weren’t being played. So there may be fewer frogs, or less variety, than the surveys suggest. The results appear in the journal Ecology. [Brett McClintock et al., http://bit.ly/9iPhUs]

Simons is working with the U.S. Geological Survey—in charge of the amphibian monitoring—to account for these false positives, and to better train the volunteers—so they don’t write down “chorus frog” [Chorus Frog sound] when all there really was were pickerel frogs. [Pickerel Frog sound] Apparently, it’s not easy being green, for humans either.

—Cynthia Graber

[The above text is an exact transcript of this podcast.]

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