Predator-prey Interactions in a Human-dominated Landscape

Abstract

Understanding animal space us is a fundamental concern in Ecology. Predator-prey interactions are a behavioral response game where predators try to find prey, and prey are trying to avoid the predators, thereby shaping animal space use and habitat selection. In the process both predator and prey tradeoff between risk avoidance and food acquisition in order to maximize their fitness. As such predator-prey dynamics have fascinated many generations of ecologists. At the same time the impact of human activities on ecosystem processes have become increasingly evident over the years and almost all habitats on earth today have been altered to some degree by humans. As a consequence humans can be considered as ecological players of ecosystem processes that shape the behavior and demography of their commensal species. In the presence of humans large top predators may be downgraded in the food chain or compete with humans for their prey. Furthermore prey species themselves have to tradeoff between risk avoidance towards humans or their natural predators. It was the goal of this thesis to look at various aspects involved in shaping the space use patterns of the Eurasian lynx (Lynx lynx) and its main prey, the European roe deer (Capreolus capreolus) and to characterize the spatiotemporal drivers of habitat selection and risk avoidance of both players in a human dominated environment. By focusing on both predators and prey I identify different key components of the behavioral response game between Eurasian lynx and European roe deer. In the first chapter I investigated how tradeoffs between risk avoidance and resource abundance in human-altered environments affect habitat selection of Eurasian lynx. In particular, I studied how spatial scale interacts with the intrinsic behavioral state of Eurasian lynx in shaping the response to temporal and spatial fluctuations in human activity and prey availability. I show that lynx tradeoff between anthropogenic risk and prey density by using areas of high prey density during times of low human disturbance. This tradeoff differs among behavioral states and is dependent on the spatial scale considered. In the second chapter I focused on the prey and tested how lynx and humans interact in shaping space use patterns of roe deer during the hunting season in fall. Multiple predators of a single prey may positively or negatively interact with each other via their prey. The same may be true for human hunters that compete with natural predators for the same prey. I explored how roe deer tradeoff between hunting and lynx predation risk and whether hunting increases the deer’s susceptibility to lynx predation. I found that roe deer avoid areas of high hunting risk during the hunting season at the expense of higher exposure to lynx predation risk. Furthermore there was strong evidence that lynx increased their hunting effort and hunting success during this time period. The results provided strong evidence that hunters facilitated lynx predation which resulted in superadditive mortality for deer during the hunting season. In environments with limited resources and time antipredator behavior may come at costs that ultimately affect prey demography. The strength of such non-consumptive effects (NCE) largely depends on the hunting mode of the predator. Ambush predators exert stronger NCE than active predators as they provide more persistent cues about predation risk than their widely roaming counterparts. While evidence comes from different taxonomic groups, evidence from large mammalian predator-prey systems is rare and equivocal. In the third chapter I looked at the occurrence and strength of NCE of the ambush predator, the Eurasian lynx on its main prey the European roe deer. According to ecological prediction I found that lynx evoked strong NCE that increased non-lynx-related mortality of roe deer in the study area. In summary, I focused in this thesis on identifying key drivers involved in shaping space use patterns of a large ambush predator and one of its main prey. Furthermore I characterized the spatiotemporal drivers of food acquisition and risk avoidance of both players in a human dominated environment. The presented results illustrate the tradeoffs between risk avoidance and food acquisition that affect decision making of all animals and show the potential costs of these tradeoffs in the form of reduced survival or reproduction. Finally the findings highlight the role of humans as ecological drivers of Ecosystem processes and may help developing efficient wildlife management plans that are needed for the conservation of large predators and their prey alike in human altered environements.