Assessing arrays of multiple trail cameras to detect North American mammals

Abstract

Motion triggered camera traps are an increasingly popular tool for wildlife research and can be used to survey for multiple species simultaneously. As with all survey techniques, it is crucial to conduct camera trapping research following study designs that include adequate spatial and temporal replication, and sufficient probability of detecting species presence. The use and configuration of multiple camera traps within a single survey site are understudied considerations that could have a substantial impact on detection probability. Our objective was to test the role that camera number (one, two or three units), and spacing along a linear transect (100 m or 150 m), have on the probability of detecting a species given it is present. From January to March, 2017 we collected data on six mammal species in Maine, USA: coyote ( Canis latrans ), fisher ( Pekania pennanti ), American marten ( Martes americana ), short-tailed weasel ( Mustela erminea ), snowshoe hare ( Lepus americanus ), and American red squirrel ( Tamiasciurus hudsonicus ). We used multi-scale occupancy modelling to compare pooled detection histories of different configuration of five cameras deployed at the same survey site (n = 32), and how the configuration would influence the probability of detecting a species given it was available at the site. Across all six species, we found substantial increases in probability of detection as the number of cameras increased from one to two (22 to 400 percent increase), regardless of the spacing between cameras. For most species the magnitude of the increase was less substantial when adding a third camera (4 to 85 percent increase), with coyote and snowshoe hare showing a pronounced effect. The influence of survey station features also varied by species. We suggest that using pooled data from two or three cameras at a survey site is a cost effective approach to increase detection success over a single camera.

High‐density camera trap grid reveals lack of consistency in detection and capture rates across space and time

“…It is assumed that observations obtained from a surveyed area, in this case the detection zone of a camera, are representative of the sampled site (MacKenzie et al 2017), and our data indicate information from a single camera is unlikely to meet this assumption when a site is defined as an area larger than the camera’s field of view. In addition, a multi‐camera approach has been shown, particularly for elusive species, to be a cost‐efficient approach (Gálvez et al 2016), and to result in significant improvements in detection probability (Stokeld et al 2016, O'Connor et al 2017, Evans et al 2019, Wong et al 2019), which should reduce bias in occupancy estimates (MacKenzie and Royle 2005, Bailey et al 2007, Guillera‐Arroita et al 2010, Neilson et al 2018) and potentially offset any reductions in total number of site samples (MacKenzie et al 2017). Recent work with multi‐camera sampling supports this, where conclusions about occupancy with single cameras were different from those based on the full multi‐camera design (Pease et al 2016) and multi‐camera sampling increases precision of occupancy estimates (Wong et al 2019).…”

“…However, little research has been conducted to assess the extent to which data collected at a single point are a consistent and repeatable measure of species occupancy or use at the landscape scale. Those few studies that have compared the effect of sampling single sites with variable numbers of camera stations have found that the use of single stations can severely limit detection probability for some species (Stokeld et al 2016, O'Connor et al 2017, Evans et al 2019, Wong et al 2019) and introduces bias in identification of key ecological factors influencing occupancy (Pease et al 2016).…”

Population density and habitat use of two sympatric small cats in a central Indian reserve

“…Camera-trap placement at trails optimizes the capture of large as well as small carnivores [24,25]. Also, the placement of two camera-traps at every site increased the detectability of these small felids [26]. Cameras were programmed to take three photographs per trigger with an interval of 5 sec.…”

Effective sampling area is a major driver of power to detect long‐term trends in multispecies occupancy monitoring

“…Due to the difficulty in precisely defining effective area, prescribing spacing and number of devices is difficult and further research is needed to inform such recommendations. Nonetheless, because of our simulations, evidence from field large-scale surveys (Zielinski et al 2013, Barry 2018, and simulations for multispecies sampling design (Sun et al 2014, Wilton et al 2014, Evans et al 2019, we suspect an efficient survey method includes clusters of >2 devices within an area such that they overlap their effective sampling areas but enlarge the likelihood of detecting an animal. For example, long-term fisher monitoring in California conducts sampling within grid cells using arrays of 3-6 track plates or trail cameras spaced 500-800 m apart.…”