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Title: PESTICIDES IN MOUNTAIN YELLOW-LEGGED FROGS (RANA MUSCOSA) FROM THE SIERRA NEVADA MOUNTAINS OF CALIFORNIA, USA

Author
item FELLERS, G - USGS
item McConnell, Laura
item PRATT, D - USGS
item DATTA, S - UNIVERSITY OF MAINE

Submitted to: Environmental Toxicology and Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2004
Publication Date: 6/1/2004
Citation: Fellers, G.M., McConnell, L.L., Pratt, D., Datta, S. 2004. Pesticides in Mountain Yellow-Legged frogs (Rana muscosa) from the Sierra Nevada Mountains of California, USA. Environmental Toxicology and Chemistry. 23:2170-2177.

Interpretive Summary: Researchers have observed severe declines in several amphibian populations in the Sierra Nevada Mountains of California. Disease, habitat loss, UV radiation, and pollution are factors that might be involved with the disappearance of amphibians over the last two decades. Mountain yellow-legged frogs (Rana muscosa) may be unusually sensitive to pollutants in the water since 2-4 years are required for tadpoles to metamorphose, and 3-4 years for frogs to reach sexual maturity. In 1997, pesticide levels were measured in Rana muscosa and surface water from two areas in the Sierra Nevada Mountains of California, USA. One area (Sixty Lakes Basin, Kings Canyon National Park) had large, apparently healthy populations of frogs. A second area (Tablelands, Sequoia National Park) once had large populations, but the species had been extirpated from this area by the early-1980s. The Tablelands is directly exposed to prevailing winds from agricultural regions to the west. Organophosphate insecticides, chlorpyrifos and diazinon, were observed primarily in surface water with higher concentrations at the Tablelands sites. In tissues, DDE was 1 to 2 orders of magnitude higher in concentration than the other organochlorines (46 +/- 20 and 17 +/- 8 ng/g wet weight at Tablelands and Sixty Lakes Basin, respectively). Hexachlorocylohexane (HCH) concentrations were unusually high at one of the Sixty Lakes Basin sites, where frogs were flourishing, indicating that HCH is not especially toxic to this species. More research is needed to discern the reason for amphibian population declines in the Tablelands area.

Technical Abstract: Researchers have observed severe declines in several amphibian populations in the Sierra Nevada Mountains of California. Disease, habitat loss, UV radiation, and pollution are factors that might be involved with the disappearance of amphibians over the last two decades. Mountain yellow-legged frogs (Rana muscosa) may be unusually sensitive to pollutants in the water since 2-4 years are required for tadpoles to metamorphose, and 3-4 years for frogs to reach sexual maturity. In 1997, pesticide levels were measured in Rana muscosa and surface water from two areas in the Sierra Nevada Mountains of California, USA. One area (Sixty Lakes Basin, Kings Canyon National Park) had large, apparently healthy populations of frogs. A second area (Tablelands, Sequoia National Park) once had large populations, but the species had been extirpated from this area by the early-1980s. The Tablelands is directly exposed to prevailing winds from agricultural regions to the west. Organophosphate insecticides, chlorpyrifos and diazinon, were observed primarily in surface water with higher concentrations at the Tablelands sites. In tissues, DDE was 1 to 2 orders of magnitude higher in concentration than the other organochlorines (46 +/- 20 and 17 +/- 8 ng/g wet weight at Tablelands and Sixty Lakes Basin, respectively). Hexachlorocylohexane (HCH) concentrations were unusually high at one of the Sixty Lakes Basin sites, where frogs were flourishing, indicating that HCH is not especially toxic to this species.