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Direct and Indirect Effects of Human-Induced Fear in a Carnivore Community

  • Author(s): Smith, Justine Alyssa
  • Advisor(s): Wilmers, Christopher C
  • et al.
Abstract

Human-induced fear in wildlife has the potential to impact animal behavior, survival, and species interactions through both direct and indirect effects. Risk-avoidance responses to fear can alter the way animals use space and resources, directly influencing their individual success and role in their ecological community. To understand ecological dynamics in systems increasingly modified and dominated by humans, a richer understanding is needed regarding the magnitude of human-induced fear in wildlife and the extent of its cascading effects.

Large carnivores act as keystone predators in many ecosystems by limiting populations of large herbivores and mesocarnivores. The loss of large carnivores can trigger trophic cascades that restructure ecological communities. However, maintaining populations of large carnivores may not be enough if human disturbances restrict the ability for carnivores to continue their functional roles. Optimal coexistence scenarios between humans and carnivores should include minimizing behavioral impacts on carnivores and preserving species interactions.

In this dissertation, I examine the nature and magnitude of human disturbances on carnivore behavior and the indirect effects of their human-induced fear. In particular, I investigate puma risk-foraging tradeoffs and their relationship to prey species on a gradient of human disturbance. I also explore the impacts of human-induced activity shifts in mesocarnivores on dietary niche partitioning. Finally, I apply my understanding of puma movement behavior and human risk-avoidance to prioritize developable lands for conservation. I conducting this work, I used or developed novel methods in citizen science, DNA metabarcoding, playback experiments, spatial analysis, and conservation planning.

The results of my work indicate that humans can cause substantial risk-foraging tradeoffs in pumas, both at the immediate and landscape scale. This causes pumas to kill more deer per year when exposed to greater disturbance, but preferably consume smaller prey when actually adjacent to development. I also found that mesocarnivores increase diet overlap when they are disturbed by human activity and become more nocturnal. I developed a new approach to prioritizing conservation acquisitions based on puma movement potential and identified high quality land parcels that could be protected by local land trusts or county planners.

My dissertation begins to explore the diversity of pathways that humans can alter animal communities by influencing the behavior of carnivores. Future work should evaluate the extent of human-induced behavioral cascades in ecosystems and determine the long-term outcomes of pervasive anthropogenic disturbance.

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