Spatial patterns of anticoagulant rodenticides in three species of medium-sized carnivores in Pennsylvania

Human influences on natural environments are now ubiquitous but manifest in multiple and unique ways depending on local environments and communities. Attempts to control, or mediate, local pests to residences or to agriculture can impart important negative consequences on systems. Secondary exposure to anticoagulant rodenticides (ARs) can cause numerous adverse effects on wild carnivores including death. No studies have quantified AR prevalence, investigated their pathway of exposure, or associations with specific location types in the northeastern U.S. We hypothesized that ARs would be found in the mesocarnivore community throughout Pennsylvania and have the greatest detection rate in highly urbanized or agricultural landscapes. From 2019 through early 2022 we collected carcasses to obtain liver samples (n=265) from three species of carnivores: bobcats (Lynx rufus (Schreber, 1777)), fishers (Pekania pennanti (Erxleben, 1777)), and river otters (Lontra canadensis (Schreber, 1777)). We used generalized linear models to test for differences in AR detection rated among species and spatial scales including the six Pennsylvania Game Commission regions and 23 Wildlife Management Units. We detected ARs in all species (44.2% collectively), but detection rates differed among species. Our study is the first to document ARs within North American river otters.