The wolf is back! Non-consumptive effects of the return of a large carnivore on the use of supplementary feeding sites by roe deer

Understanding how prey species tradeoff predation risk and resource acquisition is particularly important for advancing our knowledge of predator–prey relationships. We investigated this by studying the use of concentrated anthropogenic resources, namely supplementary feeding sites, by roe deer Capreolus capreolus before and after grey wolf Canis lupus recolonisation in an area of the eastern Italian Alps. We used camera traps to monitor roe deer visits to feeding sites, where ad libitum food was provided, before and after wolf recolonisation, in winter and spring, to control for seasonal effects. First, we compared the daily cycle of visits using circular statistics. We then used generalised linear mixed models to assess roe deer, duration of visits, and tendency to congregate at feeding sites as a function of wolf presence and season. Roe deer became more diurnal after wolf recolonisation, particularly in winter, while in spring they tended to concentrate their visits around dusk and dawn. Roe deer visits to feeding sites decreased from winter to spring, but only after wolf recolonisation, while their duration was shorter in spring when wolves were absent than in any other period. Roe deer grouping at feeding sites decreased from winter to spring, especially after wolf recolonisation. These results show that roe deer have changed their resource use behaviour following wolf recolonisation, adopting a range of behavioural tactics that could mitigate predation risk, while maintaining resource acquisition when more profitable. The increase in diurnality may reduce the temporal overlap with wolves' predominantly nocturnal activity; access to the resource-rich, but fairly exposed sites mainly occurred during the most limiting season, or with solitary visits. We call for further research to understand whether other unmeasured processes contribute to shaping the observed patterns, such as demographic decline and fine-scale behavioural adjustments (e.g. increased vigilance).