Habituation reverses fear-based ecological effects in brown bears (Ursus arctos)

Abstract

Fear induced by human activity is increasingly becoming recognized to influence both behavior and population biology of wildlife. Exposure to human activity can cause animals to avoid human-dominated areas or shift temporal activity patterns, but repeated, benign exposure can also result in habituation of individuals. Habituation is typically viewed as a negative potential consequence of human interactions with wildlife, with effects such as increased vulnerability of habituated animals to predation. Concurrently, the advancement of the understanding of the ecology of fear has shown reduced fitness in species because of behavioral changes in responses to fear of predators-including humans. Here, we test how habituation and fear drive the foraging ecology of brown bears (Ursus arctos) feeding on Pacific salmon (Oncorhynchus spp.) in Southeast Alaska, USA. We used motion-detecting trail cameras at salmon spawning areas across a gradient of human disturbance to record human and bear activity at fine spatial and extended temporal scales. Higher human activity was associated with increased nocturnality of non-habituated bears, likely leading to suboptimal foraging, but had no effect on habituated individuals. For the top 20% of sites for which human activity was greatest, an average of 78.7% of the activity of non-habituated bears was nocturnal, compared with an average of only 10.2% of the activity of habituated individuals. Habituation of brown bears in this system alleviated perceived risk and avoidance of human activity, allowing habituated individuals to overcome their fear of human presence and maximize foraging opportunities. While habituation may lessen some of the deleterious effects of human activity on large carnivores, the long-term effects of habituation may be negative, as habituated individuals may be at greater risk of depredation. Future research should examine whether habituated bears and their lower perceived risk of human activity ultimately experience smaller population-level effects of human disturbance than non-habituated individuals.