Collaborative Study Measures Effects of Invasive Bullfrogs on Native Amphibians and Pathogens of Conservation Concern

Authors: Blake R Hossack
January 24, 2023

A new collaborative study provided evidence that invasive, non-native American Bullfrogs influence the occurrence of native amphibians and increase occurrence of pathogens, including ranaviruses and amphibian chytrid fungus (Bd). These pathogens can cause lethal diseases of amphibians and have been linked with widespread population declines. ARMI scientists partnered with collaborators from Arizona Game and Fish Department, US Fish and Wildlife Service, Turner Endangered Species Fund, University of Arizona, Washington State University, and National Autonomous University of Mexico (UNAM) to analyze water samples from 233 sites in the southwestern USA and northern Sonora, Mexico, for the presence of environmental DNA (eDNA). Federally threatened Chiricahua Leopard Frogs and Western Tiger Salamanders were 8 times and 2 times, respectively, less likely to occur at sites where bullfrogs occurred. Ranaviruses were 10 times and Bd was 2.5-times more likely to be present at sites with bullfrogs than without bullfrogs. These results provide evidence that bullfrogs reduce occurrence of native amphibians and can increase occurrence of pathogens. This information can clarify risks for native species and aid in the prioritization of conservation actions.


Hossack, B. R., E. B. Oja, A. Owens, D. Hall, C. Cobos, C. L. Crawford, C. S. Goldberg, S. Hedwall, P. E. Howell, J. Lemos-Espinal, S. MacVean, M. McCaffery, E. Muths, A. H. McCall, C. Mosley, B. H. Sigafus, M. J. Sredl, and J. C. Rorabaugh. 2023. Empirical evidence for effects of invasive American Bullfrogs on occurrence of native amphibians and emerging pathogens. Ecological Applications e2785.

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