Non-consumptive effects of predation in large terrestrial mammals: Mapping our knowledge and revealing the tip of the iceberg

Studies on invertebrates and small vertebrates demonstrated the underappreciated importance of the non-consumptive effects (NCE) of predators on their prey. Recently, there has been a growing interest for such effects in large vertebrates. Here, we review the empirical literature on large carnivore-ungulate systems to map our knowledge of predation NCE (from trait modification to the consequences on prey populations), and identify the gaps in our approaches that need to be fulfilled to reach a comprehensive understanding of these NCE. This review reveals (i) biases in the studies towards North American (and to a lesser extent African) ecosystems, protected areas, and investigation of NCE by wolf Canis lupus (and to a lesser extent African lion Panthera leo); (ii) a diversification of the systems studied in the past decade, which led to contrasted conclusions about the existence of NCE; (iii) that most existing work studied the effects caused by one predator only, even in ecosystems characterized by a rich carnivore community; and (iv) that the majority of the literature on NCE focused on the anti-predator behavioural responses of prey, whereas this is only the tip of the iceberg of NCE. Indeed, little is known on the other NCE components (energetic costs, stress, reproduction, survival, and population dynamics) and the links between the different components. Linking anti-predator behavioural responses to demography is thus the key challenge ahead of us to fully understand the NCE of predators on their prey in large mammals.