UC Santa Cruz

In many of the world’s natural areas, humans now play, work, or live alongside wildlife with measurable effects on their physiology, behavior, and ecology. In particular, there is growing evidence of human-induced changes in the energetics, movement, and space use of many wildlife species, including large bodied predators, suggesting that fear of humans is a common phenomenon. For large carnivores, movement can be energetically expensive such that slight variations in the physical landscape can have profound impacts on the energy cost of movement. Large carnivores also face significant mortality risk from the human “super predator”, and resulting fear-based changes in space use may exert energetic costs by affecting how, where, and to what extent carnivores move when in proximity to humans.

In this dissertation, I integrate these two factors to understand how competing demands around energy and risk shape the behavior and spatial ecology of free-ranging pumas (Puma concolor). In particular, I quantify the joint effect of the physical and risk landscapes on the fine-scale movement of pumas and evaluate whether short-term costs drive landscape-level patterns of space use. I also examine whether pumas optimize energy economy when traveling on challenging terrain and the degree to which they cope with increased movement costs near humans. Results show that the combination of the physical and risk landscapes drives short-term movement costs for pumas, and that short-term costs, particularly those stemming from human-induced risk, scale up to influence long-term space use at the landscape scale. Further, pumas use energetically efficient movement pathways where possible, however, in areas of increasing risk from humans they adopt energetically sub-optimal paths characterized by high energy but low efficiency movement behavior. This pattern reflects a trade-off between risk avoidance and the energy costs of movement that results in a constriction of overall space use for individuals experiencing consistently high movement costs. These findings demonstrates that, along with physical terrain, predation risk plays a primary role in shaping an animal’s “energy landscape” and suggests that fear of humans may be a major factor affecting wildlife movements worldwide.

In addition, I evaluate the concurrent effects of the human footprint (development) and presence (activity) on wildlife behavior as well as model where and when the immediate presence of people, and thus disturbance, is likely to be greatest outside developed areas. Results demonstrate that, for many species, human presence and human footprint are not equivalent in their impacts on wildlife habitat use and behavior, with these two forms of anthropogenic disturbance in many cases having opposing effects on occupancy and/or activity. In particular, several carnivores, including pumas, avoided developed areas but were more likely to occupy sites with high human presence (potentially due to increased access to trails) by increasing nocturnality. By contrast, synanthropic species were more likely to occupy sites with higher building density, consistent with use of anthropogenic resources, but were substantially less detectable in areas with high human presence. Further, I found that human presence beyond developed areas to be extensive and concentrated in protected areas suggesting human impacts on wildlife may be more widespread in the region than anticipated. Given the prevalence of development and human activity in wildlands, complete avoidance of people is likely impossible for many species in the region and thus negative impacts on wildlife from human disturbance is likely high.

The research presented in this dissertation provides an important extension of recent attempts to quantify the effects of the landscape on animal movement costs by highlighting that, without accounting for predation risk, “energetic landscapes” may overlook much of the energetic cost of navigating complex environments, especially those dominated by humans. In addition, human activity is increasing in most natural ecosystems, and this work underscores the need to rigorously quantify human activity and clarify its effects on wildlife behavior in landscapes where presence of people is widespread.