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Patuxent Wildlife Research Center

Amphibian Malformations

Amphibian malformations have been increasingly found and reported over the past decade. Malformed amphibians have been documented in all states within the Northeast region. Based on North American Reporting Center for Amphibian Malformations (NARCAM) data, hotspots for malformations in the Northeast (i.e., states with the greatest number of positive reports of malformations) include Vermont, New Hampshire, Massachusetts, and upstate New York. Rana clamitans with possible malformationHowever, this may simply represent more extensive sampling in these states compared to others. Malformations may be environmentally-induced by exposure to parasites (trematodes), xenobiotic chemicals such as pesticides and/or metabolites, naturally-occurring chemicals, ultraviolet radiation, temperature extremes, disease, or may be determined genetically.

Surveys for malformed amphibians typically target early life stages (larvae/tadpoles and recent metamorphs), as it is thought that severely malformed adults would have a reduced probability of survival and hence would be harder to find. Anyone who finds malformed amphibians is encouraged to enter their observations into the NARCAM database.

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What we have found

At one site at the USDA Beltsville Agricultural Research Center in 2001, we documented malformation rates of 2% for green frog metamorphs (14 malformed of 706 total examined) and 4% for spotted salamander adults (17 malformed of 435 total examined). Extreme malformations included missing lower jaws and holes in lower jaws (see pictures).

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What we are doing

NE ARMI personnel enter amphibian malformation data into NARCAM and ARMI databases and send severely malformed amphibians to the USGS National Wildlife Health Center in Madison, WI, where Dr. David E. Green examines and diagnoses the malformed amphibians. At sites where extreme or high incidences of malformations have been documented, we are working with Drs. Carol Meteyer and Linda Trueb to determine how the malformation develops and which factors may influence its development.

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What you can do

The most important data to collect is a detailed description of the malformed amphibian (documentation using photography is recommended) and to record how many normal individuals of the species you encountered at the site compared to the number of malformed individuals (malformation rate). It is important to report this information to the NARCAM web site, which provides useful information on amphibian species identification and types of malformations encountered in the field. If an amphibian malformation is severe (e.g., multiple limbs, missing jaws or holes in throat) or if you find a high percentage of malformed amphibians at a site (e.g., > 5% of at least 40 amphibians examined at a site), this might signal an environmental problem that should be reported to local or state wildlife health specialists.

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Related Information

National Wildlife Health Center
Host-pathogen Biology and the Global Decline of Amphibians

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Page Contact Information: Evan Grant
Page Last Modified:11/02/2009