The influence of fine-scale topography on detection of a mammal assemblage at camera traps in a mountainous landscape

Abstract

Changes in topography, such as terrain elevation and slope, are an important source of landscape complexity influencing the ecology of animals, particularly in mountainous landscapes. In such landscapes animals navigate changes in elevation and slope in their daily movement. Despite the importance of topographic variation, studies of animal ecology in mountainous landscapes tend not to explicitly consider those effects on species detection. We deployed a broad-extent, coarse resolution camera-trapping system across a landscape with considerable complexity and quantified the influence of topographic variables on detection probability conditional on occurrence for multiple mammal species. Specifically, we examined the fine-scale effects of terrain steepness and topographic position (i.e. ridges, mid-slopes or valleys) on detection probability for 14 mammal species at camera-traps. We found that detection probability increased on gently sloping terrain for six species and decreased on the steepest slopes sampled for three of these species and three additional species. Among four other mammal species, detection probability changed according to local topographic position though the directionality of these responses varied among these species. Several species, primarily meso-carnivores as well as larger-bodied species, like mule deer and black bears, were more detectable on gentle slopes than flat terrain. This pattern suggests that many species may use moderately steep terrain for the resources or heterogeneity they provide. Topographic position had comparatively less effect on species detection probabilities, suggesting that this variable does not have a strong effect on fine-scale space use of animal species in mountainous regions. These relationships suggest that researchers should consider local terrain when siting camera traps in mountainous landscapes and analyzing survey data from such landscapes. Studies that compare the detection of mammal species at cameras deployed in close proximity will improve our understanding of fine-scale topographic effects on mammal movement and detection.