Assessing the effectiveness of trail cameras with attractants to detect northeastern mammals

Camera traps are a cost-effective tool for large-scale and long-term population monitoring of mammals. Either bait or lure is often used to attract animals in front of a camera; however, the relative efficiency of these two attractants, or their combination, is not well understood. Our objective was to determine the optimal attractant setup for maximizing detection probabilities of mammals in the northeast USA. We conducted a camera trapping project in northern Maine, USA, from August to November 2018, and tested three distinct attractant treatments against a control. Sampling stations were a minimum of 5 km apart, and consisted of four camera units spaced 100 m apart, and paired with one of the four setups: (1) bait plus lure (treatment), (2) bait (treatment), (3) lure (treatment), and (4) camera only (control). Detection data on 11 species of mammals were collected from 41 stations and analyzed through multi-method occupancy models. We totaled 4280 photo-trap-nights and captured 37,781 images. Results showed that the combination of bait plus lure was the most effective for increasing detection probability of carnivores. Specifically, bait plus lure proved to be particularly effective for mustelid species, while lure was particularly effective for American black bear (Ursus americanus). While attractant usage was shown to be ineffective for increasing detection probability of non-carnivores, it also did not decrease effectiveness. Based on our results, we recommend the simultaneous use of both bait and lure as attractants when conducting camera trapping work on mammals. The combination of bait and lure appears to maximize detection of carnivore species, while simultaneously having minimal effects on the detection of other taxa.