Differences in behavioral responses to sub-lethal pesticide concentrations in amphibians and a potential predator.
Kerby, Jacob*,1, Sih, Andy1, 1 University of California, Davis, CA, USA
ABSTRACT- Sub-lethal effects of contaminants have become an increasing focus for research investigating the causes of amphibian declines. This study examines differences in behavioral responses in two species of larval frogs, the Pacific tree frog (Hyla regilla) and the foothill yellow legged frog (Rana boylii) when exposed separately to four different commonly used pesticides (atrazine, carbaryl, chlorpyrifos, and diazinon) at four different concentrations (0, 50, 500, and 5000 ug/L). Significant differences in behavioral responses (activity level, refuge use, position) occur between the two species for some pesticides but not others. R. boylii consistently exhibited behavioral shifts at lower concentrations of pesticides when compared to H. regilla. We also evaluated behavioral responses of H. regilla tadpoles in the presence of a predator, the western mosquitofish (Gambusia affinis) when both were simultaneously exposed to diazinon at four concentrations (solvent control, 0, 5000, and 10,000 ug/L). In this interaction, pesticide-exposed predators significantly reduced activity and predation rates on H. regilla. Exposure to pesticide alone had no significant direct effect on tadpoles. However, tadpoles exposed to both predator and pesticide significantly increased activity and reduced refuge use when compared to treatments with predators only. These differential responses between both predators and competitors when exposed to different sub-lethal levels of pesticides likely have large impacts on community dynamics and may provide insights on explaining some amphibian population declines.
Key words: predator, behavior, pesticide, amphibian
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