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 trade-off 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 model the occurrence, 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 since the return of the wolf, 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).