The influence of prey availability, habitat attributes and other factors on space use by social carnivores
Ecology is the study of the processes resulting in the observed distribution and abundance patterns of organisms across the landscape. These patterns reflect individual movement decisions, the cumulative effects of which result in population-level patterns that drive systems. Of profound importance therefore, is determining the factors that influence these decisions. This is vital for apex, social predators given their potential to strongly influence the spatial patterns of their prey both directly through the predation process and indirectly mediated by their prey’s behavioural responses to perceived predation risk. These influences can resonate across trophic levels. In this PhD thesis I investigate the factors affecting space use decisions by two apex social carnivores in contrasting systems with an emphasis on directly comparing the most fundamental potential drivers - prey distribution and habitat attributes that enable efficient prey capture. I employ a novel methodological approach by creating population-level utilization distributions constructed from those at the individual group-level, as a measure of predator space use. This allows for broad-scale patterns to be assessed while retaining individual group-level variation and reflecting territoriality. Results indicate that social predator space use is consistently influenced by habitat attributes that should improve predation efficiency either by increasing the vulnerability of potential prey or by spatially anchoring predator search to compensate for unpredictable prey movement. While habitat attributes are influential across seasons and at a variety of spatial scales, I also find that prey availability is an important additional predictor of predator space use under certain ecological conditions, specifically when overall prey abundance is high. This implication of a possible threshold in prey density impacting predator spatial behaviour is intriguing and opens a fertile area of further study. I also clearly demonstrate that predators are adapting territory size, not group size, to local habitat quality, suggesting an adaptive way to balance tradeoffs between the costs of territorial defense and gains of resource acquisition. Overall my thesis provides compelling evidence identifying and meaningfully comparing important factors underlying predator space use and contributes positively to the ongoing effort to gain a comprehensive understanding of the behavioural processes that define and structure systems.