Efficacy and Decay of Lures for Increasing Detections of Carnivores at Camera Traps

Accurate estimates of abundance and occupancy are crucial for effective management and conservation but are often hampered by low detections, especially for cryptic species like carnivores. While low detections can be accounted for during statistical analysis, improving detections in the field is the best way to reduce uncertainty. Camera traps are an effective, noninvasive method of monitoring wildlife, but often do not detect every animal present. Using attractants (i.e., bait or lure) with camera traps can increase the likelihood of capturing an animal (specifically a carnivore) that is present. Carnivores react differently to attractants based on their hunting style and more work is needed to tailor attractants to specific species. We tested two scent lures: sardines and fatty acid tablets, against a control of no lure to determine if either lure increased detections of five common carnivore species, bobcat (Lynx rufus), coyote (Canis latrans), gray fox (Urocyon cinereoargenteus), raccoon (Procyon lotor), and striped skunk (Memphitis memphitis). We randomly distributed lures over 257 camera trap sites for 10,145 trap nights over two years. We further tested if detections of carnivores decreased as the lure decayed over time by modeling detections against lure age. Detections of gray foxes and raccoons increased with both sardines and fatty acid tablets while bobcats, coyotes, and striped skunks did not respond significantly to either lure. We expect lures to become less effective as their smell becomes weaker and aim to find the optimal length of deployment for each lure. Our analysis highlights the importance of designing a study to fit a focal species and optimize the timing of attractant deployment. We hope our results decrease the level of effort while increasing the efficacy of future research.