Predator Exclusion Cages as Visual Attractants to Mammalian Predators 

Authors and Affiliations: 

Seanna Jobe (Graduate, University of North Carolina Wilmington), Dr. Rachael E. Urbanek (Faculty Advisor, University of North Carolina Wilmington), Paul Hillbrand (Sea Turtle Program Coordinator, Bald Head Island Conservancy), Dr. Elizabeth S. Darrow (Chief Scientist, Bald Head Island Conservancy), Emily Abernethy (Park Ranger, Fort Fisher State Recreation Area). 

Summary: 

Sea turtle nest depredation is a growing concern along the North Carolina coast and while several designs have been published, no one predator exclusion cage (PEC) is 100% effective. We hypothesized that PECs may increase the chance of depredation on sea turtle nests by acting as a visual stimulus that mammalian predators later associate with food. To test this hypothesis, we installed 10 PECs on Bald Head Island (BHI), North Carolina (Fig. 1) between 11 May and 30 June 2021. We replicated 2 PEC designs (5 times each) that were previously tested against depredation on the island (Fig. 2). PECs were not baited or placed over a turtle nest so that the presence of PECs was the only novel stimulus. We deployed PECs in a randomized pattern <10 m from the dune vegetation and 1-100 m apart to simulate natural distances between sea turtle nests on South Beach (Fig. 3). PECs were deployed in an incremental temporal pattern consistent with the natural increase in sea turtle nests throughout the season. Each PEC was accompanied by a camera trap to detect predator presence and to observe their behavior for a total of 58 camera nights. We also deployed an array of 10 cameras with no PECs as controls on West Beach (Fig. 4) for a total of 55 camera nights. In the week prior to the first PEC deployment, coyotes visited a higher proportion (paired t₇ = 3.36 P = 0.014) of South Beach cameras (0.26 ± 0.06; mean ± SE throughout) than on West Beach (0.10 ± 0.01; Fig. 5). Similarly, we observed, on average, 35% more coyote events (paired t₇ = -2.38 P = 0.048) on South Beach (0.40 ± 0.12) than on West Beach during this time (0.14 ± 0.07; Fig. 6). Over the remaining time of the study while PECs were incrementally deployed, there was no difference in the average percent of cameras visited (South Beach: 0.15 ± 0.02; West Beach: 0.15 ± 0.02) or the average number of coyote events (South Beach: 0.24 ± 0.11; West Beach: 0.21 ± 0.11) on the beaches (paired t₇ = -0.72-0.16 P = 0.475-0.876). These preliminary results indicate that the PEC designs used our study did not act as a visual stimulus to attract coyotes. Our next steps will be to analyze paired t-tests to compare the percent of sites visited and average number coyote visits per camera for each incremental PEC deployment. Then, will compare behavioral data for coyotes during this study to coyote behavior at real sea turtle nests during the same period of time. Knowledge gained from our study will help sea turtle managers when considering future PEC design and implementation.

The North Carolina Trappers Association provided $1,000 through the Furbearer Research Grant program to help purchase the bait, supplies, and cover travel expenses for the North Carolina State University student conducting the research. 

The purpose of this study was to test the effectiveness of baited-tube camera traps to detect weasels in North Carolina. The study also increased our knowledge of the proper tools needed to determine the distribution and abundance of weasels.  As an attractant, 10 x 30 cm tubes staked into the ground were baited with raw chicken liver and Caven Gusto’s scent lure ~1m from a camera trap.  Cameras were placed in suitable habitat (dense cover) in six game lands in North Carolina, aiming for 20 sites per game land.  Results found no weasels at four game lands, but did obtain one long-tailed weasel (M. frenata) detection at South Mountain Game Lands and Pisgah Game Lands.  Other species detected regularly includef Virginia opossum (Didelphis virginiana), white-footed mice (Peromyscus leucopus), and Northern raccoon (Procyon lotor).  The results of this study will evaluate the effectiveness of baited-tubes cameras to detect weasels in the region and contribute to our understanding about the distribution and abundance of weasels in North Carolina.

There are two species of weasels present in North Carolina, the least weasel (Mustela nivalis) and the long-tailed weasel (Mustela frenata).  Long-tailed weasels are believed to be statewide.  Least-weasels are believed to be in the higher elevation portion of the mountains.  Despite a statewide presence, there are few confirmed records of weasels in North Carolina.  The Museum of Natural Sciences only has 72 records of weasels with only 3 occurring after 2000.  Since 1990, the North Carolina Wildlife Resource Commission has 25 records of weasels in the state.  The North Carolina Candid Critter project, which has placed more than 8000 cameras throughout the state, has only detected 4 weasels.  Unbaited camera traps are likely not effective at detecting weasels.  Weasels are rarely observed in the southeastern USA and it is unknown if this is because they are rare, cryptic, in decline, or difficult to survey.  However, the lack of detections on the NC Candid Critter may also be due to camera placement and camera brand used on this project. Baited cameras may be needed to detect weasels in an area, as well as increase the ability of the camera to detect the weasel.

Effects of different attractants and human scent on mesocarnivore detection at camera traps

Bracy W. Heinlein, Rachael E. Urbanek, Colleen Olfenbuttel and Casey G. Dukes

Abstract Context.

Camera traps paired with baits and scented lures can be used to monitor mesocarnivore populations, but not all attractants are equally effective. Several studies have investigated the efficacy of different attractants on the success of luring mesocarnivores to camera traps; fewer studies have examined the effect of human scent at camera traps.

Aims.

We sought to determine the effects of human scent, four attractants and the interaction between attractants and human scent in luring mesocarnivores to camera traps.

Methods.

We compared the success of synthetic fermented egg (SFE), fatty acid scent (FAS) tablets, castor oil, and sardines against a control of no attractant in luring mesocarnivores to camera traps. We deployed each attractant and the control with either no regard to masking human scent or attempting to restrict human scent for a total of 10 treatments, and replicated treatments eight to nine times in two different phases. We investigated whether: (1) any attractants increased the probability of capturing a mesocarnivore at a camera trap; (2) not masking human scent affected the probability of capturing a mesocarnivore at a camera trap; and (3) any attractants increased the probability of repeat detections at a given camera trap. We also analysed the behaviour (i.e. speed and distance to attractant) of each mesocarnivore in relation to the attractants.

Key results.

Sardines improved capture success compared with the control treatments, whereas SFE, castor oil, and FAS tablets had no effect when all mesocarnivores were included in the analyses. Masking human scent did not affect detection rates in the multispecies analyses. Individually, the detection of some species depended on the interactions between masking (or not masking) human scent and some attractants.

Conclusions.

Sardines were the most effective as a broad-based attractant for mesocarnivores. Mesocarnivores approached traps baited with sardines at slower rates, which allows for a higher success of capturing an image of the animal.

Implications.

Human scent may not need to be masked when deploying camera traps for multispecies mesocarnivore studies, but researchers should be aware that individual species respond differently to attractants and may have higher capture success with species-specific attractants

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