Field Guide to Amphibian Malformations

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View an online version of the USGS "Field Guide to Malformations of Frogs and Toads with Radiographic Interpretations" by C.U. Meteyer.

The USGS field guide provides photographs and x-rays of the major types of malformations commonly encountered among recently metamorphosed frogs in the United States.

The field guide distinguishes between malformations caused by predation and those caused by other factors and may be used as an aid in reporting amphibian malformations.

North American Reporting Center for Amphibian Malformations (NARCAM)

In 1996, a group of Minnesota school children on a field trip to a local pond made a disturbing discovery: dozens of frogs with missing limbs and eyes, extra limbs and underformed limbs.   Reports surfaced from other areas of the nation that frogs with similar malformations were present.

In the past decade, extensive research into the malformations phenomena has been undertaken by scientists from government, academic, and non-profit sectors. Scientists have identified several variables potentially contributing to malformations, such as diseases, ultraviolet radiation, contaminants, and predation.   It is probable that malformations are not the result of a single cause, but are rather brought on by different factors in different regions.  The debate over malformations phenomena is far from conclusive, however, and research continues.

In cooperation with the greater scientific community, this Web site serves as a resource for people to learn about amphibian malformations phenomena in North America and for citizens to report on the health of local amphibian populations.

If you have observed malformed amphibians, we encourage you to report your sightings to the North American Reporting Center for Amphibian Malformations (NARCAM) using this site's online reporting form.  You can also get information on the extent of malformation reports received to date, including geographic distribution, information on the types of malformations found and species affected in each area.

Founded and developed by the U.S. Geological Survey's Northern Prairie Wildlife Research Center, NARCAM is now managed by the Southeast Information Node of the U.S. Geological Survey's National Biological Information Infrastructure (NBII) in partnership with the University of Georgia's Savannah River Ecology Lab.

Amphibian Malformations: What Are the Causes?

Researchers suggest multiple causes are likely to blame for worldwide reports of amphibian malformations, and factors leading to malformations at one site may differ from causes at another site. At this time, three major environmental factors identified as the causes of malformations include:

According to the U.S. Geological Survey's National Wildlife Health Center, malformations in amphibians arise from environmental factors that affect individuals at the larval stage of development. Observed malformations have included missing forelimbs or hindlimbs, extra forelimbs or hindlimbs, incompletely formed forelimbs or hindlimbs, and missing eyes.

U.S. Fish and Wildlife Service Abnormal Amphibian Surveys

Northern leopard frog (Rana pipiens) with polymelia (extra limb).
[Photo: Laura Eaton-Poole, U.S. Fish & Wildlife Service]

The U.S. Fish and Wildlife Service's Division of Environmental Quality is actively involved in studying amphibian declines and abnormalities. To better study amphibians and the concerns facing them, the Fish and Wildlife Service has developed standard operating procedures (SOPs) for abnormal amphibian surveys on U.S. Fish and Wildlife Service wildlife refuges. The Fish and Wildlife Service's Amphibian Declines and Deformities Web page provides more information about how the U.S. Fish and Wildlife Service works to conserve threatened and endangered amphibians.

Found a Malformed Frog?

Have you found a frog, toad or salamander that has extra or missing legs, missing eye or a jaw, or looks otherwise deformed, "mutated," or abnormal?

The U.S. Geological Survey invites you to submit an online report. Professional researchers and citizen-scientists alike can contribute reports, which are reviewed and verified by herpetologists at the Savannah River Ecology Lab.

All report contributors remain anonymous. Malformation data is published to a verified report database searchable by species name, state or county, or malformation type.

Savannah River Ecology Lab

Savannah River Ecology Lab logo [Copyright: University of Georgia]

The Herpetology Program of the University of Georgia Savannah River Ecology Lab, under the leadership of Dr. Whit Gibbons, provides herpetological expertise and quality assurance/quality control for all malformations reports submitted to NARCAM. All reports are reviewed for completeness, accuracy, and integrity before they are made available for public access and review.

The NBII Program is administered by the Biological Informatics Program of the U.S. Geological Survey
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