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Pesticides Found in Amphibians from Remote Areas in California

A Pacific Chorus frog in meadow located in Yosemite National Park
A Pacific Chorus frog in meadow located in Yosemite National Park. Photo credit: Devin Edmonds, USGS.

Amphibians from remote locations in California have accumulated several current-use pesticides, including fungicides, in their bodies. A team of U.S. Geological Survey (USGS) scientists recently reported on field results in the journal Environmental Toxicology and Chemistry. Two fungicides, pyraclostrobin and tebuconazole, and the herbicide simazine were detected frequently in amphibians from all sites sampled. The USGS study is the first to document the occurrence of these fungicides in amphibians and one of the first studies to measure fungicides in tissue.

Frog populations are declining worldwide and pesticides are thought to be one of the contributing causes, acting singly or in combination with other stressors. Not much is known about the exposure of frogs to pesticides, especially in remote areas (areas away from where pesticides are applied). The scientists looked at pesticides in Pacific Chorus frogs (Pseudacris regilla) and their habitat (water and sediment) in seven remote, high-elevation locations in California (including Giant Sequoia National Monument, Yosemite National Park, and Lassen Volcanic National Park). Chorus frogs were studied because they are found in a broad geographic area, they are still relatively abundant, and USGS scientists have been investigating their decline for over a decade. Fungicides (pesticides used to control fungal diseases) were found in adult male frogs from all sites. The sites sampled were downwind of California’s Central Valley; a potential cause of exposure may be from pesticides transported to these locations via precipitation and dust. Data generated from this study indicate that amphibians residing in these remote locations are exposed to and capable of taking up current-use pesticides.

This study was funded by the USGS Toxic Substances Hydrology Program, Amphibian Research and Monitoring Initiative, and Wildlife: Terrestrial and Endangered Resources Program.

USGS scientist collecting water samples from a pond
USGS scientist collecting water samples from an amphibian monitoring site in Livermore, California. Photo credit: James Orlando, USGS.


Smalling, K.L., Fellers, G.M., Kleeman, P.M., and Kuivila, K.M., 2013, Accumulation of pesticides in Pacific Chorus Frogs (Pseudacris regilla) from California‚Äôs Sierra Nevada Mountains, USA: Environmental Toxicology and Chemistry, v. 32, no. 9, p. 2026-2034, doi:10.1002/etc.2308 (public access pdf file — — journal Web page).

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