MA2 Amphibian Research and Monitoring
Ballroom F, Level 4
8:00 AM - 12:00 PM, Monday, 10 November 2003
Chair: Rostad, Colleen ,
Co-chair: Battaglin, William ,
(018) Diazinon altered predator-prey interactions between a fish and two amphibians.
Kerby, J1, Wehrmann, A1, Sih, A1, 1 University of California, Davis, CA, USA
ABSTRACT- We examined the effects of sub-lethal levels of the insecticide Diazinon on interactions between a predatory fish and two amphibians. Two 48-h experiments were performed in tubs containing one of four Diazinon concentrations (0, 0.5, 1.0 mg/L and a methanol solvent control) and Western mosquitofish (Gambusia affinis) with either Pacific treefrog tadpoles (Hyla regilla) or Tiger salamander larvae (Ambystoma tigrinum). In the absence of fish, pesticide treatments did not directly affect the behavior or survival of tadpoles. However, in the presence of fish, tadpoles exposed to pesticide treatments were more active and experienced greater survival than those exposed to non-pesticide treatments. Higher tadpole activity and survival is attributed to Diazinon significantly decreasing fish movement and attack rate. Similar effects were found when salamander larvae and fish were combined. Once again, Diazinon did not have any significant direct effects on amphibian behavior, but did reduce fish movement and attack rate. In the presence of fish, salamander larvae in non-pesticide treatments did not suffer reduced survivorship as did treefrog tadpoles, but did have significantly greater external gill loss due to attacks by fish. These results demonstrate that sub-lethal levels of Diazinon can indirectly alter amphibian behavior and survival by modifying predator behavior.
Key words: Amphibian, Diazinon, Behavior, Multiple stressor