Agricultural land use and reproductive behaviour constrain responses to summer thermal stress in a large herbivore

Agricultural land use and climate change are major global threats to terrestrial biodiversity. However, their interactive effects on synanthropic species are only recently being addressed. Behavioural plasticity is the most likely candidate mechanism for coping with rapid environmental change, yet behavioural adjustments may be insufficient when multiple anthropogenic pressures, such as human land-use and rising temperatures, coincide with strong life-history constraints. We investigated how agricultural land use shaped the availability of thermal refuge and mediated responses to high temperatures during the mating season in roe deer (Capreolus capreolus), a large herbivore present in most European agricultural landscapes. We demonstrated that woodland provided more efficient thermal refuge than anthropogenic vegetation such as hedges or tall crops. The combination of high temperatures, agricultural land-use and reproductive constraints were dealt with differently by males and females. Females adjusted their habitat use and activity patterns to limit exposure to high temperatures, causing a greater loss in the availability of efficient cover habitat for females with little access to woodland. Males, however, did not modify their habitat use, but strongly decreased activity and distance travelled on hot days, probably due to strong reproductive constraints. We show that the extent to which behavioural plasticity mitigates the effects of high temperatures is context-dependent and may not always suffice in anthropized landscapes where thermal buffering habitats are rare. Restoring woodland patches and hedges, while considering how climate change modifies the use of substitute habitats shaped by human activities, will be key in promoting species’ resilience within agricultural areas.