The Silence of the Frogs

Insight on the News, May 24, 1999 by Jennifer Kabbany

Biologists are sounding the alarm about the death of frogs from Canada to Australia.

As a young boy growing up in California, Gary Fellers spent his summers exploring the Sierra Nevada Mountains, and continued as a graduate student. The area has changed over time. "When I go back to the Sierra Nevadas now," he says, "the decline in the amphibian population is dramatic."

A research biologist for the U.S. Geological Survey in Point Reyes National Seashore, Calif., Fellers is one of many scientists looking into the disappearances and deformities among the frog population. "Frogs are part of the food chain, and where frogs are declining, snakes are declining, too," he says. "We're already seeing the ripple effect; we haven't tracked it all the way up the food chain yet."

Scientists noticed in 1993 that the frog population was declining in the southeastern United States. Others reported an increase in deformed frogs in Minnesota -- some with missing legs, others with protrusions growing from their backs. Similar phenomena have been cited in Canada and other parts of the world, including Australia and Central America.

Why are frogs in trouble? Theories range from pollutants to fungus, but no one has managed a definitive answer. "Try being able to define what's going on in a group of animals which don't like to be counted," says biologist Sam Droege of the Patuxent Federal Wildlife Research Center in Maryland. "Yes, there are plenty of indications that there is a real problem. Yes, people still find frog malformations. But nobody is willing to say, `This is the cause.'"

But the problem could be an early warning sign about dangers that might affect humans, according to Droege. "If frogs are dying, are they drinking different water or breathing different air than me? No."

David Gardiner, a biologist at the University of California at Irvine, thinks the culprit could be retiniods, a chemical derived from vitamin A commonly used for acne treatments. Retiniods are known to cause human deformities. Women prescribed Accutane, an acne medication based on retiniods, are advised to practice birth control while on the treatment. Frogs may be absorbing the chemical through their permeable skins.

Another culprit could be the chytrid fungi. "That scares us," says Droege, who believes it may spread through schools of fish or human researchers acting as unknowing hosts. "It's a primitive fungi which nobody knows anything about, which has been shown to wipe out communities of frogs in Australia and Central America."

Still another factor could be agricultural chemicals. Researchers from Trent University in Ontario, Canada, created environments similar to those of frogs and tadpoles in the wild -- drainage ditches, ponds and other wet spots around orchards and farms -- then exposed frog eggs and tadpoles to a common pesticide. They found the frogs experienced high death rates and unusual growth and development. Researchers hope to set up experiments that would follow tadpoles through metamorphosis to assess whether early, low-dose exposures to such pesticides may be responsible for some of the deformities plaguing North American frogs.

Whatever the cause, the effect of the disappearance of the amphibians is troubling. "In a theoretical sense, if frogs are the dominant member of an ecosystem, then lots of things eat them and they eat lots of things;" Droege says. "Now they're gone. Is that the collapse of the Roman Empire? No, but it could be the beginning of the collapse of the Roman Empire."

Scientists studying the problem have asked for a $5.6 million increase in funding from the Interior Department in fiscal 2000. Frog studies can be expensive. "If you take a frog and send it to a commercial lab, it can cost as much as $1,000 per sample," says Fellers.

A new Website has been created so average citizens can count frogs in their backyards, then report findings to www.mp2-pwrc.usgs.gov/frogwatch. "People can count them for three minutes a day, a couple times a week;" Droege says. "It's educational and fun for kids."