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.

One size does not fit all: a novel approach for determining the Realised Viewshed Size for remote camera traps

“…Although we would not expect camera traps to decrease performance until -20°C or below (Reconyx, 2022), it is worth noting that other research has observed camera traps performing best around 0°C, where higher false-negatives occur in positive temperature ranges (Jacobs & Ausband, 2018), and negative temperature ranges and associated weather can contribute to decreased performance (Maile et al, 2023). Conducting jog-tests during other seasons and within a greater range of forest types and habitat will likely contribute to detecting statistical differences in environmental covariates and help determine if a cameras ECA varies more substantially across space and time (e.g., as in McIntyre et al, 2020; Moeller et al, 2023; Moll et al, 2020; Sultaire et al, 2023; Urbanek et al, 2019).…”

“…Although vegetation cover in our study had a relatively lower influence on ECA (Table 2, Figure 6), the importance of different predictor variables, will likely depend on the geography and habitat conditions of the study. For example, topography (Sultaire et al, 2023) and weather (Madsen et al, 2020) have been found to influence camera trap capture probabilities in some geographies. Thus, if implementing our method, researchers should consider all potential important predictor variables that may influence capture probability at their study sites.…”

“…For example, Reconyx Hyperfire camera traps, a very popular brand in wildlife research, market a viewshed area extending up to 30 m from the camera trap and 40° angle perpendicular to the camera’s lens, an area approximating 315 m 2 (Reconyx 2022; Figure 1A). In reality, environmental factors such as habitat structure, topography, and vegetation (Moeller et al, 2023; Moll et al, 2020; Sultaire et al, 2023), will dictate a cameras viewshed area for each unique location where cameras are placed (Apps and McNutt 2018; Urbanek et al 2019; Figure 1B).…”

Evaluating ecosystem protection and fragmentation of the world's major mountain regions

“…As ecosystems and species shift their distributions to track changing climates, sharp topographic constraints and bottlenecks from human‐induced habitat fragmentation will decrease species’ abilities to persist and adapt. High physiographic and habitat diversity in mountains also amplifies the inadequacy of spatial prioritization and planning for use with relatively coarse analytical units, like ecoregions (e.g., Dinerstein et al., 2017), because they fail to capture critical features, such as landforms characteristic of mountains (Sultaire et al., 2022).…”