RESEARCH PAPER https://doi.org/10.1071/WR22196 Effects of sardines as an attractant on carnivore detection and temporal activity patterns at remote camera traps Anna C. Siegfried A , Stephen N. Harris A, * , Colleen Olfenbuttel B and David S. Jachowski A For full list of author affiliations and declarations see end of paper *Correspondence to: Stephen N. Harris Department of Forestry and Environmental Conservation, Clemson University, Clemson, SC 29634, USA Email: esenaitch@gmail.com Handling Editor: Pablo Ferreras Received: 10 December 2022 Accepted: 25 September 2023 Published: 17 October 2023 Cite this: Siegfried AC et al. (2023) Wildlife Research doi:10.1071/WR22196 © 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing. ABSTRACT Context. Adding an attractant to remote camera traps has become a popular method to increase detections of cryptic carnivores. However, there is ongoing debate about whether this practice can bias the behaviour and activity patterns of these species. Aims. Our aim was to determine how using a popular attractant at camera traps could affect carnivore detection probabilities and temporal activity. Methods. We used an experimental design in which we randomly set half of our camera traps on arrays at two sites in western North Carolina with an attractant: canned sardines in oil. Halfway through the survey season, we switched which camera traps had sardines and which did not. We estimated detection probability for each carnivore species observed using occupancy models, and we used kernel density estimations to evaluate changes in diel activity patterns between camera traps with and without an attractant. Key results. We found that when sardines were used at camera traps, detectability of bobcats (Lynx rufus), coyotes (Canis latrans), northern raccoons (Procyon lotor), Virginia opossums (Didelphis virginiana), and eastern spotted skunks (Spilogale putorius) more than doubled, but there was little or no effect on striped skunk (Mephitis mephitis) detectability. Of the species we most frequently detected (coyotes, raccoons, and opossums), activity patterns between camera traps with and without a sardine attractant overlapped moderately to highly, and a significant effect on diel activity patterns was observed only for raccoons. Conclusions. Use of attractants can greatly increase the probability of detecting nearly all carnivores at camera traps. The effects of attractants on diel activity patterns are species-specific, with two of our three most-detected species unaffected by their use, suggesting that attractants can be used to effectively study these behaviours in some carnivore species. Implications. A sardine attractant can increase the detection of many carnivore species, using camera traps, without causing a significant deviation of diel activity patterns, thus allowing for unbiased investigations into most species’ spatio–temporal behaviour in the Appalachian Mountains – and likely other systems. Keywords: attractant, camera, Canis latrans, carnivore, detection, Didelphis virginiana, Lynx rufus, Mephitis mephitis, Procyon lotor, sardine, Spilogale putorius, temporal activity. Introduction Carnivores tend to move across large areas, leading to frequent intra- and inter-specific interactions, so large-scale studies are often necessary to understand carnivore assemblages. However, large-scale studies are difficult to execute because of low detection probabilities associated with cryptic or low-density species occupying large areas. Remote camera traps (hereafter, camera traps) are a non-invasive method that can be used to monitor and investigate mammalian carnivores (Gompper et al. 2006; Robinson et al. 2017); they are relatively easy to deploy and tend to require less labour and time in the field than traditional invasive techniques such as live capture (Kays and Slauson 2008). Managers and researchers can use data from camera traps to examine occupancy, behaviour, and population density of various carnivore species (Thorn et al. 2009; Lazenby et al. 2015; Braczkowski et al. 2016; Zapata-Ríos and Branch 2016). However, some species like spotted skunks (Spilogale spp.; Dukes et al. 2022) and weasels (Mustela spp.; Reed 2011; Mos and Hofmeester 2020) remain difficult to detect.