Complex Effects of Human-Impacted Landscapes on the Spatial Patterns of Mammalian Carnivores

Abstract

In the face of an expanding global human footprint, mammalian carnivores have become vulnerable to the effects of large-scale landscape change. Throughout North America, wide-ranging terrestrial carnivores have experienced significant species declines and range retractions. Understanding the complex and interacting effects of human-caused habitat disturbance on highly mobile species remains an ongoing challenge for ecologists. To address these challenges, studies commonly select a focal species to examine the adverse effects of human disturbance. Due to the paucity of multi-species study, little is yet known about the relative role interspecific interactions play within communities of carnivores in human-altered systems. In an effort to address this knowledge gap, I examined occurrence patterns of one species known to be sensitive to human disturbance – the wolverine – and compared occurrence patterns among multiple carnivores across a gradient of increasing human land use within a rugged and heterogeneous landscape in the Canadian Rocky Mountains of Alberta. I surveyed carnivore occurrence by combining remote camera trapping and non-invasive genetic tagging. Using a systematic grid based design, medium to large sized carnivores were detected over an area approximately 15,000km2. Consistent with the literature, I found wolverines to be less likely to occur outside of protected areas boundaries and with increasing human-caused landscape disturbance. Contrary to recent climate-focused hypotheses, the spatial pattern of wolverine occurrence was best explained by cumulative effects. When modeling multiple carnivore occurrence across this spatial gradient of human land use, no generality in response was observed. However, a consistent and distinct dissimilarity in response to natural and anthropogenic landscape features was found between wolverine and coyote. The patterns of occurrence led me to infer that habitat condition in the more human-altered systems found along eastern slopes of the Canadian Rocky Mountains is less suitable for some more sensitive species and benefits more human-adapted species. I further hypothesized that an indirect and additive effect of human disturbance is increased interspecific competition between co-occurring carnivores that differentially respond to changes in habitat condition. My results emphasize that by broadening our scope to investigate both single and multiple species, ecologists and managers may better understand the full suite of factors influencing current and future distribution patterns.