Indirect effects of predation in human-modified landscapes

• Main Author: Sahlén, Ellinor
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2016
• Subjects: Ecology; Alces alces; Ursus arctos
• Online Access: https://pub.epsilon.slu.se/13726/; https://pub.epsilon.slu.se/13726/1/Sahlen_e_161019.pdf

Large carnivores affect prey species, with cascading effects on entire ecosystems. In anthropogenic regions large carnivores come into conflicts with humans, especially in rural areas where farming and hunting traditions are widespread. As a result, large carnivores have been eradicated from many regions across their historical distribution. Here, I explore human-predator-prey interactions, and how large carnivores and humans affect the space use, behavior, and long-term stress of ungulate prey in a region greatly modified by humans. Experimental and observational data are used to quantify behavioral and physiological antipredator responses of prey in areas with and without large carnivores. Further, I synthesize the effects of large carnivores on ecosystems in anthropogenic landscapes, and outline implications of large carnivore recovery for extant prey species and humans. I found that prey in my study areas responded to increased perceived predation risk, even where the focal carnivore species (brown bear Ursus arctos) had been absent for over a century. Prey selected more open habitats in areas where they perceived predation risk to be higher. Further, I noted that risk posed by brown bears had the potential to cascade across trophic levels and impact on tree recruitment. Higher temperatures and human infrastructure were associated with higher hair cortisol (stress hormone) levels in moose Alces alces, which may have implications with respect to the globally rising temperatures and the increasing anthropogenic disturbances across many landscapes. In anthropogenic regions, humans may greatly impact ungulates, predator-prey interactions, and the ensuing cascades. One way to mitigate human impacts is to preserve old-growth forests, because these tend to have lower human activity (less roads and no set rotation times) and cooler microclimates. Another important aspect is the mitigation of human-large carnivore conflicts, as human perceptions of large carnivores may be the most important factor determining the outcome of large carnivore recolonizations.