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Mari K. Reeves,^1,2 Christine L. Dolph,³ Heidi Zimmer,⁴ Ronald S. Tjeerdema,² and Kimberly A. Trust¹

¹U.S. Fish and Wildlife Service, Anchorage Fisheries and Ecological Services Office, Anchorage, Alaska, USA; ²Ecology Graduate Group and Department of Environmental Toxicology, College of Agricultural and Environmental Sciences, University of California, Davis, Davis, California, USA; ³Water Resources Science Program, University of Minnesota, St. Paul, Minnesota, USA; ⁴Western Washington University, Huxley College of the Environment, Bellingham, Washington, USA

Abstract
Background: Skeletal and eye abnormalities in amphibians are not well understood, and they appear to be increasing while global populations decline. Here, we present the first study of amphibian abnormalities in Alaska.

Objective: In this study we investigated the relationship between anthropogenic influences and the probability of skeletal and eye abnormalities in Alaskan wood frogs (Rana sylvatica) .

Methods: From 2000 to 2006, we examined 9,269 metamorphic wood frogs from 86 breeding sites on five National Wildlife Refuges: Arctic, Innoko, Kenai, Tetlin, and Yukon Delta. Using road proximity as a proxy for human development, we tested relationships between skeletal and eye abnormalities and anthropogenic effects. We also examined a subsample of 458 frogs for the trematode parasite Ribeiroia ondatrae, a known cause of amphibian limb abnormalities.

Results: Prevalence of skeletal and eye abnormalities at Alaskan refuges ranged from 1.5% to 7.9% and were as high as 20% at individual breeding sites. Proximity to roads increased the risk of skeletal abnormalities (p = 0.004) but not eye abnormalities. The only significant predictor of eye abnormalities was year sampled (p = 0.006) . R. ondatrae was not detected in any Alaskan wood frogs.

Conclusions: Abnormality prevalence at road-accessible sites in the Kenai and Tetlin refuges is among the highest reported in the published literature. Proximity to roads is positively correlated with risk of skeletal abnormalities in Alaskan wood frogs.

Key words: abnormality, Alaska, amphibian, Lithobates sylvaticus, malformation, national wildlife refuge, Rana sylvatica, wood frog. Environ Health Perspect 116:1009–1014 (2008) . doi:10.1289/ehp.10963 available via http://dx.doi.org/ [Online 21 April 2008]

Address correspondence to M.K. Reeves, U.S. Fish and Wildlife Service, Anchorage Fisheries and Ecological Services Office, 605 W. 4th Ave., Room G-61, Anchorage, AK 99501 USA. Telephone: (907) 271-2785. Fax: (907) 271-2786. E-mail: mari_reeves@fws.gov.

We thank C. Berg, F. Broerman, C. Caldes, J. Connor, P. Cotter, V. Davis, M. DeZeeuw, M. Fan, J. Hall, P. Jensen, S. Jensen, B. Johnson, S. Keys, S. Kovach, N. Maxon, B. McCaffrey, E. Moreno, J. Morton, M. Nemeth, D. Payer, M. Perdue, J. Ramos, A. Rappoport, J. Stout, H. Tangermann, and C. Wall for assistance in the field ; D. Larson and D. Sutherland (University of Wisconsin, La Crosse) for parasitology ; D. Green [U.S. Geological Survey (USGS) ], L. Guderyahn (Ball State University) , and M. Lannoo (Indiana University) for radiography ; J. Bromaghin [U.S. Fish and Wildlife Service (U.S. FWS) ] and N. Willits [University of California, Davis) for statistical consulting ; and L. Ball (USGS) , R. Hinzman (U.S. FWS) , M. Nemeth (LGL Alaska Research) , and three anonymous reviewers for review of the manuscript.

This work was supported by the U.S. FWS, Division of Environmental Quality.

The authors declare they have no competing financial interests.

Received 7 October 2007 ; accepted 21 April 2008.