Deer and climate change: impacts and perspectives

Climate change is one of the most important threats to biodiversity both for the relevance of the impacts and the speed of the process. Deer are widely affected by climate change even if the outcomes of the interaction with a given species are equivocal. Cold-adapted species are in general more susceptible to climate-change impacts, but even eurythermic species such as roe deer can be affected in their population dynamics. Both indirect effects, such as the mismatch between vegetation flushing and birth date, or the reduction of food accessibility, and direct ones, such as the impact of temperature causing heat stress, on activity rhythms, habitat selection and ultimately food intake, can have important consequences. In deer species, the ability to cope with these changes is dependent on the timing of resource acquisition, being different in capital and income breeder, but also on the breeding biology with special reference to the ability to shift reproduction in time. A number of consequences are caused by the impact of climate change on populations and individuals; notably, relevant shifts in species distribution have been described in different parts of the world. Moreover, changes in young and adult body size, in juvenile survival, in population dynamics and in the timing of biological cycles, such as rutting time or birth season, have been observed in a number of species. Changes in hunting regulations and management or conservation actions may be necessary to buffer the impacts of climate change, and some species or populations may be threatened with extinction or extirpation if proper measures of conservation are not adopted.