Abstract
Knowledge about habitat selection is crucial for ungulate management and conservation to handle competing land use. Thermal tolerance and access to food are two important drivers of habitat selection. Thus, moving into thermal shelter when temperatures increase may result in reduced energy intake e.g. mature forests providing thermal shelters through high canopy cover, but lower amounts of forage than more open habitats. Body size affects heat sensitivity, with larger animals being more sensitive. In this study, we investigated ambient temperature mediated habitat selection in three differently-sized, sympatric, deer species (moose, red deer and roe deer) during spring and summer in Sweden. We also assessed the trade-off between thermal shelter and forage availability. We used data from GPS-collared animals with a combination of land cover and airborne LIDAR data to quantify canopy cover as a proxy for thermal refuge and shrub cover as a proxy for forage availability. We found that temperature influenced habitat selection in all three deer species however with divergent patterns. During warmer daily temperatures, moose and red deer selected areas with more canopy cover for thermal shelter, however showing opposite patterns during warmer nights, suggesting patterns of thermoregulatory behaviour. Roe deer showed no influence of high temperatures on canopy cover selection however,, selected more strongly for areas with high canopy cover during colder temperatures i.e. showing contrasting patterns compared to moose and red deer, suggesting that canopy cover may be relatively less important for roe deer as temperature increase. All three species selected for shrub cover during warmer temperatures, which can provide both high forage availability and shade over bed sites for smaller deer species. Our findings indicate that canopy cover and shrub cover habitats appear to be important as temperatures increase, but their significance varies among species. Furthermore, our study highlights the complexity behind habitat selection in sympatric ungulate species, food intake and predation risk.