Effect of Lure on Detecting Mammals with Camera Traps

Abstract

Motion-triggered camera traps are subject to imperfect detection and thus camera-trapping surveys often try to increase species detectability as part of the study design. One possible way to increase detectability is to use lures, which may encourage a species to investigate a given area. Yet the effectiveness of lures is primarily grounded in anecdotal support. We quantified the effect of a common olfactory carnivore lure on the detectability of mammals near Chicago, Illinois, USA, during 27 August 2018-25 September 2018. We deployed 2 camera traps per site, spaced apart by 100 m, to assess whether lure can modify detectability both within and between sites. At each camera location, we changed lure treatments every 7 days and placed either a lure or a non-lure control in view of each camera following a fully crossed design. For analysis, we developed single-season occupancy models with 3 distinct observational models to quantify whether lure increased the number of days a species was detected, decreased the amount of time to first detection, and increased the number of images collected. Lure induced a subtle change in detectability. Virginia opossum (Didelphis virginiana) responded most to the presence of lure; their daily detection probability rose by roughly 5% and the number of opossum images nearly doubled. However, the effect of lure was often negative for prey species. When lure was present, eastern cottontail (Sylvilagus floridanus) daily detection probability decreased by 5% and they were photographed 63% less often. Likewise, eastern gray squirrel (Sciurus carolinensis) arrived 70% later to a camera trap if lure was present and were photographed 14% less. By using multiple criteria, we were able to better understand how wildlife respond to lure while camera-trapping more thoroughly than would be possible with a single metric. Our results show that lure may not be as effective as expected in terms of increasing detectability, but the choice to use lure should depend on several factors, including the density of the study species, species life history, and the dynamics between the species studied.

Mammals adjust diel activity across gradients of urbanization

“…To increase the detection probability of each species we placed one synthetic fatty acid scent lure in the camera line of sight, and lures were replaced on 2-week intervals if missing to remain consistent throughout the study. However, Fidino et al, 2020 later found that this type of lure has little to no effect on the detectability of most urban mammals. We used observation data collected between January 2017 and December 2018.…”

Effectiveness of a commercial lure to attract red fox

“…Nonetheless, attractants could alter movements of animal, bringing them to areas where (Schlexer 2008;Holinda et al 2020): in turn, this could introduce sampling bias in some estimators, either for occupancy of for abundance (cf. Fidino et al 2020). Furthermore, the essence must be carefully selected because some lures could have different effects on both prey and predators, possibly decreasing their detectability (Fidino et al 2020).…”

Occurrence and Abundance of an Apex Predator and a Sympatric Mesopredator in Rural Areas of the Coastal Range of Southern Chile

“…Their camera records were considered as independent events when consecutive images that contained the same species were recognizable as different individuals, a method used in several studies [60,64,68]. The use of lures is a widespread method in camera trapping, but optimizing the detectability of a target species can produce bias in calculating abundances, as the species behavior may be altered, or some species may be attracted whereas others may be repelled [88][89][90][91].…”