Assessing the effectiveness of attractants to increase camera trap detections of North American mammals

Abstract

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.

Evaluating species-specific responses to camera-trap survey designs

“…Attractants such as baits (food reward) and lures (non-food reward) are often used in carnivore studies to increase encounter events (Schlexer 2008). However, responses to attractants can vary greatly among species, making choice of attractants an important aspect of study design in multi-species studies (Du Preez et al 2014, Ferreira-Rodríguez and Pombal 2019, Buyaskas et al 2020, Holinda et al 2020. Seasonal timing of the survey can influence inference regarding habitat use or activity patterns (Kays et al 2020) and affect encounter frequencies, particularly for species that hibernate or exhibit seasonal differences in density (e.g.…”

Umbrella effect of monitoring protocols for mammals in the Northeast US

“…The bait consisted of American beaver ( Castor canadensis ) carcasses, which were cut to standard size ( = 0.22 kg) and protected by a suet cage approximately 2 m in front of the camera at an average height of 30 cm above the ground. In a previous study we demonstrated that the simultaneous use of bait and lure increased the detection probability of carnivore species without impacting non-carnivore mammals 23 . Specifically, we found that for mustelid species and for the black bear, the combined use of a bait and lure drastically increase detection, as an example the probability of detecting a marten increased from 0.1 to 0.5.We deployed survey stations in the summer season for > 15 days, and during the following winter season for > 15 days.…”

“…Our previous work has shown that the use of bait and lure clearly maximizes detection of carnivores (mustelids in particular) without affecting detection of non-target species 23 . A more neutral approach (no bait or lure) would likely work too, however in our case detection probabilities would have been extremely low, leading to very high sampling efforts 23 . Further, we emphasize that our sampling unit was a transect with three cameras, which maximizes detections and reduces the variance in parameter estimates 1 , 22 .…”

Empirical evaluation of the spatial scale and detection process of camera trap surveys

“…Furthermore, attraction to bait can introduce heterogeneity due to behavioral variation among individual animals within [11] and between species [1,25] and temporal variation in detection probability as the bait degrades or is eaten. Nonetheless, these problems might be offset by increased detection probability and by keeping an animal in front of the camera long enough for a good picture, especially for single species studies where comparisons across the community are less important [4]. Placing camera traps along fine-scale habitat features (e.g.…”