Movement and space-use responses of a large herbivore to experimental alteration of resource availability

Resource acquisition is a key factor governing patterns of animal movement. While the link between spatio-temporal resource patterns and movement behaviour has been widely documented for migration, our understanding of home ranging behaviour in relation to resource dynamics has been limited by challenges of quantifying resource heterogeneity at fine spatio-temporal scales. In this study, we addressed this issue by analysing the movement responses of a resident large herbivore in response to an in situ manipulation of a high-quality, concentrated food resource. Specifically, we fitted roe deer (Capreolus capreolus) with GPS collars in the Eastern Italian Alps and recorded their fine-scale movement responses to an alteration of feeding site accessibility, for a total of 25 animal-years. The experiment involved identifying, for each animal, a familiar feeding site, whose accessibility was transitorily restricted (i.e., closed) while maintaining the availability of forage at alternative feeding sites. First, we tested whether individuals altered their spatial behaviour to track dynamical changes in resource availability. Experimental closure led to larger, spatially-shifted home ranges, resulting from more exploratory movements. Individual roe deer compensated the loss of their familiar feeding site by using alternative ones, and by doing so maintained their overall use of these concentrated resources. Our results demonstrate that roe deer actively track resource dynamics, and rapidly adjust their space-use and movement behaviour in response to changes in resource availability. Second, we showed that individual resource preferences mediate these behavioural adjustments: individuals characterized by a high preference for feeding sites exhibited larger space-use shifts and stronger changes in resource use in response to the resource manipulation. In contrast, sex had relatively minor influence on the observed patterns. Third, we investigated the role of site familiarity in roe deer foraging decisions. We found that space-use and resource use during the post-closure period were restored to pre-closure patterns, thereby providing evidence for the inherent benefits of site familiarity to animals maintaining a home range. Together, our results establish the connections between movement, space-use, individual preference, and the spatio-temporal pattern of resources in deer home ranging behaviour.