A systematic review of methods for studying the impacts of outdoor recreation on terrestrial wildlife

Outdoor recreation is a known source of disturbance to many wildlife populations. We systematically reviewed 126 relevant papers that study the impact of outdoor recreation on wildlife, focusing on terrestrial wildlife (birds excluded) to assess the different methodological approaches adopted by researchers. We characterised the research methods into seven categories (direct observation, indirect observation (field-based), telemetry, camera traps, physiological measurement, trapping, and simulation). We find that direct observation is the most commonly used method to capture human-wildlife interactions, followed by the use of telemetry, and camera traps. The animals most commonly studied were ungulates, and the orders Carnivora and Rodentia. Studies typically captured data over longer periods (median 54 months) when using trapping methods; other methods exhibited shorter study durations (median 22 months). The size of the animal under study appears to influence how methods are chosen, with larger species often being studied using telemetry methods. We highlight advantages and disadvantages of each method depending on the aims of the study, the focal species, and the type of outdoor recreation. Our review highlights the need for simultaneous measurements of both human activity and wildlife response. We also recommend that researchers consider how to capture both short- and long-term impacts on animal welfare. Our findings should guide applied wildlife conservation and management research in scenarios where human-wildlife interactions lead to conservation issues.