Mystery of the Malformed Frogs -- Background Information

Frog Malformations Research

Is the number of malformed frogs increasing? Scientists from the Minnesota Pollution Control Agency soon became involved in the study of malformed frogs. To determine whether the level of abnormalities observed at the Minnesota farm pond was a random event, or whether the incidence of malformed frogs was actually increasing, they needed frog surveys from more areas. By the end of 1996, the Minnesota Pollution Control Agency had received 175 reports of malformed frogs from two-thirds of Minnesota's counties. The agency also began to receive reports of malformations from other states.

However, some scientists countered the uproar about the recent reports with evidence that amphibian abnormalities have been observed since the 1700s. They believed that the current malformations observed in Minnesota and elsewhere were a normal or random occurrence. Despite these precautions, the majority of herpetologists now agree that the preponderance of recent reports is alarming and that we are probably seeing an increased incidence of frog malformations over what would normally be expected.

In response to the concern about amphibian malformations, the Biological Resources Division of the U.S. Geological Survey in the U.S. Department of Interior formed the North American Reporting Center for Amphibian Malformations (NARCAM). Scientists, as well as informed students and volunteers, can contribute to our knowledge about amphibian malformations by participating in this program.

What is the cause of amphibian malformations? The mystery of the malformed frogs is not yet solved, although many explanations have been proposed. To date, scientists have found evidence that may link malformations in tadpoles and frogs with a number of factors, including pesticides and other contaminants, ultraviolet radiation, and parasites. It is also possible that these factors interact to cause the malformations. For example, increased ultraviolet radiation caused by ozone depletion may transform nontoxic chemicals into toxins. Scientists at government agencies and universities continue to study the possible causes of malformations.