Spatiotemporal patterns of anticoagulant rodenticide exposure in bobcats across the northeastern United States.

Anticoagulant rodenticides are a pervasive threat to non-target wildlife health, with exposure in predators frequently driven by the interface of human development and wild spaces. Long-term regional data are needed to understand how exposure rates vary in relation to changing regulation and public use of rodenticide compounds. We analyzed opportunistic samples collected from 2013-2024 across the northeastern United States to quantify rates of anticoagulant rodenticide (AR) contamination in bobcats (Lynx rufus) and identify spatial hot spots of exposure. We detected seven AR compounds in 352 bobcats (59% exposed) across 4 states; the highest levels of exposure were in New Hampshire and Vermont. Our spatial clustering algorithm indicated localized hot spots of AR detection across New Hampshire, Vermont, and New Jersey, with New York clusters appearing cold by comparison. Exposed bobcats had 1-4 AR compounds (mean = 1.07, sd = 1.17) in their system and exposure rates varied by state, age, and sampling source (harvest versus roadkill) but not sex. Predicted odds of AR exposure increased by approximately 35%, and the predicted number of compounds increased by approximately 17%, for each year increase in bobcat age. Despite federal restrictions on the use of second-generation ARs going into effect during the course of our study, AR detection rates increased steadily over time at a rate of 25% per year. Our observations were similar to broad spatial patterns of AR exposure in northeastern fisher (Pekania pennanti), reflecting the ubiquity of AR exposure across predators with differing habitat use. This work provides baseline exposure information for a mesocarnivore species of interest, highlights a concerning trend of increasing AR exposure over time, and contributes to the growing evidence of widespread rodenticide contamination of non-target wildlife.