Proceedings of the Vertebrate Pest Conference

A 15-year study of carnivores in an urban landscape in southern California has revealed a high incidence of exposure of non-target wildlife to anticoagulant rodenticides (ARs). All carnivore species studied, including mountain lions, coyotes, bobcats, and gray foxes, have tested positive for exposure to the toxicants. Anticoagulant residues have been detected in post-mortem liver samples at a rate of 83-93% of individuals tested, for coyotes, bobcats, and mountain lions, the three species for which we have extensive sampling. We have also documented mortalities caused directly by exposure to ARs in all four species, particularly in the canids. In both felid species, we found a positive correlation between AR exposure and mange disease, specifically notoedric mange. The incidence of fatal mange infection in bobcats has been at epizootic levels since 2002 in our study area, and more recently outbreaks of the disease have been documented in several other populations in California, all apparently (where testing has been done) in association with exposure to ARs. There are no previously reported instances of epizootics of notoedric mange in any wild felid population. Carnivore exposure to these toxicants appears to be largely secondary (or tertiary, as may be the case in mountain lions) through consumption of their natural prey. In our most recent work, we have evaluated AR exposure of carnivore prey species, including rodents and lagomorphs. We have documented exposure in ground squirrels and woodrats, both of which are regularly consumed by gray foxes, coyotes, and bobcats. Overall, we have found widespread exposure of non-target wildlife to these toxicants, with potentially significant consequences for some species.