Assessing anti-predator decisions of foraging eastern chipmunks under varying perceived risks: the effects of physical and social environments on vigilance

Animals foraging under risk have to trade-off resource acquisition and predator avoidance. Environmental factors can modulate the level of risk and should thus influence the expression of anti-predator behaviours such as vigilance. In this study, we investigated the effects of physical and social environments on eastern chipmunks' (Tamias striatus) vigilance, by varying the perceived risk through playback experiments of alarm calls and neutral environmental sounds, and by integrating habitat and weather characteristics, as well as neighbour density. Chipmunks showed higher levels of vigilance when foraging in more open habitats, under high wind conditions, when they heard alarm calls and when surrounded by a high neighbour density. The effects of wind intensity and neighbour density on vigilance were also stronger during the broadcast of alarm calls rather than neutral sounds. Our results emphasize how both the physical and social environments can modify risk perception and therefore risk-taking decisions of foraging individuals.