Proceedings of the Vertebrate Pest Conference

In 2016, the Wildlife Investigations Lab initiated a statewide mountain lion health surveillance study to understand population health and anticoagulant rodenticide (AR) exposure. Exposure to first-generation (FGARs) and second-generation (SGARs) anticoagulant rodenticides are common in predators such as raptors, wild canids (i.e., foxes and coyotes) and bobcats. However, statewide data regarding rodenticide exposure in these species, including mountain lions, have been limited. Our objectives were to determine the statewide prevalence and geographic distribution of AR exposure in necropsied mountain lions. We used liquid chromatography/mass spectroscopy to detect rodenticides in liver samples from 111 (77 male: 34 female) mountain lion carcasses from 37 counties that died between Feb 2016 and Feb 2017. Necropsied carcasses were lions taken on depredation permits, vehicular strike, public safety, or other reasons. Overall, we detected ARs from the liver tissue of mountain lions from 35 counties with 105 of the 111 (94.5%) lions having exposure. We detected FGARs in 81 individuals (73%) from 33 counties and SGARs in 102 individuals (92%) from 35 counties. Seventy-eight individuals (70%) were exposed to both SGARs and FGARs while 6 (5%) individuals had no detectable AR concentration. Of the FGARs detected, diphacinone was the most common and was observed in 67% of sampled individuals. Brodifacoum was the most common SGAR, detected in 90% of sampled individuals. Exposure to FGARs was correlated with exposure to SGARs (χ2 = 5.8, p = 0.01). Exposure to ARs was not associated with lower body condition score. Although our study represents only one year of data, we demonstrate that exposure to both FGARs and SGARs is widespread in California’s mountain lions. We recommend continued AR screening of livers from mountain lion carcasses to further enhance our understanding about the relative contributions they may have on population health. Continued monitoring would also measure the effectiveness of regulatory changes intended to reduce non-target wildlife exposure to rodenticides