Determination of Malathion Aerial Drift and Associated Effects to the Endangered Wyoming Toad (Bufo baxteri) Using Surrogate Woodhouse's Toads (Bufo woodhousii) at Mortenson and Hutton Lake National Wildlife Refuges and Potential Reintroduction Sites
Kim Dickerson T. Huang M. Allen Michael J. Hooper
The endangered Wyoming toad is confined to Mortenson National Wildlife Refuge in southeast Wyoming. Pesticide aerial drift from mosquito control activities adjacent to the refuge may be partially responsible for the toad's decline. Spray cards had detectable malathion concentrations at three sites but survival of surrogate Woodhouse's toads was 100% and mean ChE activities in brain and plasma samples did not differ significantly among sites. Righting trial times in surrogates among sites after spraying were not significantly different. Terrestrial invertebrate abundance results were inconclusive but differences in aquatic invertebrate relative abundance before or after spraying were not significant except at the reference site and Meeboer Lake. Our results indicate that, although some malathion drift is occurring, the toads were not exposed to malathion concentrations great enough to reduce adult survival, affect predator avoidance behavior, or reduce their food source. The data also provide needed information on ChE activities in amphibians.
ASTM - American Society for Testing and Materials
http://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP11177S.htm, 288 KB
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