Magazine article Sierra

What's Wrong with the Frogs?

Magazine article Sierra

What's Wrong with the Frogs?

Article excerpt

Scientists are narrowing in on pesticides as the cause of deformities

At first it seemed like a bad dream or an oddball freak of nature. In August 1995, a class of Minnesota middle-school students on a field trip to a farm wetland found a frog with a missing leg. Then another and another. By the end of their trip, the students had caught 22 frogs, half of which had missing or deformed legs.

The students reported their observations to the Minnesota Pollution Control Agency. Within weeks of their widely publicized discovery, more reports of deformed frogs poured in from other areas. Now the Great Lakes region, New England, the Pacific Northwest, and the St. Lawrence River valley in Quebec are North American hot spots for deformed frogs. Whodunit? A final verdict has yet to be reached, but the leading suspects are pond-dwelling parasites called trematodes and chemical contamination from pesticides and other sources.

Scientists have linked parasites to frog deformities in the Pacific Northwest and the Northeast but exonerated them elsewhere. In the case of the Minnesota frog deformities, a research group led by National Institute of Environmental Health Sciences biochemist James Burkhart points to a still unidentified chemical or combination of chemicals as the most likely culprits. The group's report, published in last December's Environmental Health Perspectives, adds to the work of other scientists who suspect pesticides or other chemicals that disrupt endocrine systems.

Meanwhile, Canadian research has identified agricultural pesticides as a main cause of frog deformations in a farm-rich area outside Montreal. Seven years ago, veterinarian Martin Ouellet began tracking the overall abundance and health of frogs in the St. Lawrence River valley, particularly in ponds on farms that use pesticides. "I was expecting to find a lot of tumors and cancers," Ouellet says, since fish in polluted waters often develop such symptoms. …

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