Territoriality and resource availability modulate the effect of conspecific encounters on the foraging behaviours of a mammalian predator

Abstract

AbstractThe probability of encountering conspecifics shapes multiple dimensions of animal behaviour. For example, territorial individuals increase vigilance, scent marking and alarm calling when approaching home range boundaries. Whether territorial predators modify their foraging behaviours with respect to the probability of encountering neighbouring territory owners is poorly understood. However, this could strongly influence the landscape of predation risk and therefore modulate predator-prey interactions. We studied the movements and behaviours of 23 resident Arctic foxes occupying neighbouring home ranges during two years of contrasting resource availability (abundant resources in 2019, scarce resources in 2022) on Bylot Island, Nunavut, Canada. First, based on simultaneous GPS tracking of individuals, we established which individuals used a territory (an exclusive area) by estimating the spatial distribution of the probability of encountering a neighbour within their home range. Second, using GPS and accelerometry data to identify prey searching and caching events, we evaluated if the probability of encountering a neighbour influenced the spatial distribution of foraging behaviours, and whether this relationship differed between territorial and non-territorial individuals. In 2019, when resources were abundant, only breeding individuals excluded other foxes from a part of their home range and could thus be considered territorial. In 2022, when resources were rare, none of the foxes reproduced and all but one were territorial. Non-territorial individuals in 2019 were less active in areas with a high probability of encounter, suggesting they searched prey less intensively and engaged in more vigilance in these areas. They were also less likely to cache prey in areas with a high probability of encounter, possibly reducing the risk of cache pilfering. We found no effect of the probability of encounter on the behaviours of the non-territorial individual in 2022. Territorial individuals in 2019 and 2022 were on the contrary more likely to be active in areas with a high probability of encounter. Yet, their probability to cache prey did not depend on the probability of encountering a neighbour, suggesting the increase in activity near borders may be related to an increase in territory patrolling rather than in prey searching. Our results suggest that Arctic foxes use different tactics to secure resources based on their degree of territoriality and the availability of resources. We highlight how the presence of resident, but non-territorial predators, whose home ranges overlap those of their territorial neighbours, may influence the distribution of predation risk by creating zones where predator density is high, potentially influencing predator-prey interactions.