An Assessment of the Potential Hazards of Anticoagulant Rodenticides to Plethodontid Salamanders

We assessed the hazards of the anticoagulants diphacinone and brodifacoum to salamanders of the family Plethodontidae or lungless salamanders. We completed this research in anticipation of an attempt to eradicate the invasive house mouse (Mus musculus) from the Farallon Islands National Wildlife Refuge, California, USA, where the endemic subspecies Farallon arboreal salamander (Aneides lugubris farallonensis) occurs. We exposed live-captured salamanders of 3 species (Aneides lugubris, Ensatina eschscholzii xanthoptica, and Batrachoseps attenuatus) to anticoagulant rodenticides by both oral and dermal exposure routes in laboratories at the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center, Fort Collins, Colorado, USA. The amount of exposure was high, simulating a worst-case scenario. There were some deaths (9 of 37 treated salamanders; 24.3% mortality). We did not observe the sublethal effects of weight loss or reduced food (cricket) consumption that has been observed in studies of other taxa (mammals and birds). Skin sloughing and sores on the undersides of certain salamanders exposed to rodenticides as well as some controls left it unclear whether this effect was caused by the anticoagulant. Following trial completion, we analyzed whole bodies of salamanders for rodenticide residues. Residue concentrations were very low (