We investigated the frequency of secondary exposure to rodenticides in raptors that provide natural pest control on farms in the Western United States. Integrated pest management IPM strategies for rodent pests frequently incorporate natural pest control provided by raptors, however, rodenticides are often applied concurrently. We have little understanding of how rodenticide exposure in raptors varies across seasons and between species in agriculture.
Furthermore, studies to date have focused primarily on spring and summer months for both understanding the role that raptors play in providing pest control and for monitoring rodenticide exposureβwhereas both occur year-round. To address these knowledge gaps, we investigated rodenticide exposure rates in hawks and owls across multiple seasons and as a function of proximity to rodenticide application sites to answer two critical questions: 1 How does barn owl rodenticide exposure and diet vary over an annual cycle?
To accomplish this task, we collaborated with ongoing barn owl research projects SW , pest management specialists, raptor biologists, and producers who are interested in developing data-driven management recommendations for raptors and natural pest control in agriculture. We conducted extensive outreach to academics, professionals, farmers, and the general public, all who stand to benefit from the results of this study. Our ultimate objective is to enhance the understanding of simultaneous use of raptors and rodenticides in agriculture on a year-round basis and communicate IPM recommendations to a wide audience.
We tested the blood of hawks and owls for circulating anticoagulant exposure to detect recent sublethal exposure from the past weeks depending on dose and compound. The results of our study indicated low rates of acute anticoagulant rodenticide exposure in barn owls across seasons, although we also documented low rodenticide use at our study sites during the study period.
While these results suggest low acute exposure rates to anticoagulant rodenticides in raptors on farms, these results must be interpreted with caution. Because we wanted to study the interaction between raptors and the normal pest management approaches on farms, we did not influence the applications of rodenticides, and therefore sampling did not necessarily align with locations or timing that baiting occurred.
