Abstract
Human land use and climate change are major global threats to terrestrial biodiversity, potentially driving interactive effects on synanthropic species. Behavioural plasticity is the most likely candidate mechanism for coping with rapid and simultaneous environmental changes, yet behavioural adjustments may be insufficient when multiple anthropogenic and climatic pressures, such as human-induced habitat loss and rising temperatures, coincide with strong life-history constraints. Throughout this thesis, we examine the combined impacts of agricultural land use, high temperatures and drought events on the behavioural adjustments of European roe deer (Capreolus capreolus) during different moments of their life history. This work combines the analyses of longitudinal data on life history traits, individual movement and environmental data collected in the field collected in a long-term study on a wild population of roe deer living in a heterogenous agricultural landscape in France. We first show that the strong behavioural plasticity expressed by roe deer enables them to adjust to the spatiotemporal variations in the landscapes of food and fear shaped by human activities. These adjustments seem to rely on mechanisms of landscape complementation and substitution between crops (e.g., maize, artificial meadows and wheat), anthropogenic wooded habitats (hedges) and semi-natural habitats providing cover (woodland). Roe deer seem to compensate for the lack of woodland in their home range by using tall summer crops (maize) during the day as a substitute cover habitat. We found that this behavioural plasticity also enabled roe deer to respond to the variations in their energetic needs, such as during lactation, as well as mitigate stressful climatic conditions, such as high temperatures and dry periods. These effects were however mediated by the amount of woodland in their home range as well as individual life history traits. Similarly, we show that agricultural land use mediated the deleterious effects of seasonal drought events on early and late juvenile body growth in contrasted ways, depending on drought timing. All of these results suggest that both agricultural land use and the temporal variations in individual internal constraints, in respect to the phenology of growth or reproduction, mediate individual and population responses to changing environmental conditions. Our works highlights the importance of considering individual life histories and the heterogeneity in local human land use when studying the responses of large herbivores to climate change. By studying the behavioural responses of roe deer to agricultural land use and its potential interactions with high temperatures and drought conditions, we underline the role of behavioural plasticity in the persistence of a common large herbivore in agroecosystems and propose different avenues to reflect on their future coexistence of wildlife with humans in a changing world.