The California red-legged frog (CRLF) (Rana aurora draytonii) is endemic to California and Baja, Mexico. The species has been extirpated from 70% of its former range and was listed as threatened under the Endangered Species Act in 1996. The US Environmental Protection Agency must determine whether 66 pesticides currently authorized for use in California may adversely affect the CRLF. A screening-level and refined effects determination (ED) was conducted for the CRLF to assess potential direct and indirect effects associated with exposure to the insecticide malathion. Our screening-level ED indicated that terrestrial-phase CRLFs are not at risk from direct exposure to malathion. A subsequent refined probabilistic ED indicated that malathion has a low probability of adversely affecting aquatic-phase CRLFs and their fish and invertebrate prey. The results of this ED indicate that risks of direct effects to CRLFs and indirect effects via reduction of prey and habitat is negligible.

Refined effects determination for the California red-legged frog (<i>Rana aurora draytonii</i>) potentially exposed to malathion

248th National Meeting (2014)

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Refined effects determination for the California red-legged frog (Rana aurora draytonii) potentially exposed to malathion