Wrong ribbit? North American Amphibian Monitoring Programs sends volunteers to listen for and count frogs and toads. But a new study shows that even expert observers (or listeners) make errors that may have skewed frog population assessments.
To get a count on animals that make noise, scientists often listen for their calls. But even expert ears make mistakes when trying to identify frogs.
Confusing two species, or hearing a frog that isn't there, is an occasional error that can have serious implications in our understanding of what is going on with a population, say researchers with the U.S. Geological Survey.
For about 10 years, the USGS's North American Amphibian Monitoring Program has sent out volunteers to listen for vocal amphibians – frogs and toads – and, based on an interpretation of the calls, record information about the amphibians' abundance and diversity. However, a new study shows that even expert observers make errors that may have skewed population assessments.
Ted Simons, a wildlife biologist with the USGS Cooperative Research Unit at North Carolina State University, said the observers' own vivid memories of hearing a particular creature at a particular time can be a liability.
"It somehow burns right into your psyche. You can go back sometimes years later and those memories just jump right back. ... Those memories can also be a source of bias when you are trying to get an accurate count," said Simons, who has done similar work analyzing the potential for misidentifications with the North American Breeding Bird Survey.