Are super-predators also super-scary? A systematic review and meta-analysis of animal responses to human interactions

Human induced rapid environmental change has been recognized as a global threat to natural systems and the organisms that inhabit them. Human hunters and fishers interact with animals in natural spaces as predators, and are more effective in capturing prey and reducing populations than natural predators overall. On the other hand, seemingly benign interactions with humans, such as tourism, may also be perceived as threatening and have negative impacts on animal populations. Here, we provide a synthesis of the current knowledge of the combined effects of lethal and non-lethal human interactions on the behavioural responses of animals in natural spaces. We conducted a systematic review and meta-analysis of literature published over the past three decades, and built a dataset to determine the relative effect of lethal and non-lethal human interactions on foraging, vigilance, and movement behaviors of wild animals. Lethal human interactions included hunting, fishing, and retaliatory killing in response to conflict, and non-lethal human interactions were distinguished as active (snorkeling, scuba diving, pedestrians, hiking, and tourists) or passive (roads, human settlements, sonar, and boat traffic). We also considered how the trophic level of the species and body size could influence the effect of human interactions on animal behavior. Our findings show that lethal human interactions had a significant effect on the behaviors of animals, causing animals that are actively hunted by humans to increase vigilance, reduce foraging, and alter movements. Both active and passive non-lethal interactions had weaker and non-significant effects on altering these behaviours of animals. Overall, our meta-analysis shows that the impact of non-lethal human activities in eliciting fear-driven behavioural changes in prey does not seem to have broad empirical support. It also suggests that the intensity of effect of the human super-predator may depend on the trophic level of affected species, or the history of the human-animal interactions in that landscape, In order to understand the nuances of these effects, systematic studies across more species and geographic regions are needed.