Warming winters disrupt bat activity and hibernation in mediterranean olive agroecosystems

Climate change is altering winter conditions in the Mediterranean, disrupting hibernation of bats and threatening their ecological functions in agroecosystems. We investigated the combined effects of rising winter temperatures and variation in habitat cover on early-winter bat activity in organic olive groves in Tuscany, Italy. Our study was conducted in 12 organic olive groves, selected to represent varying levels of surrounding semi-natural habitat cover (SNH low <30% and SNH high >30%) within a 250 m buffer, and included 4 additional reference sites located in full semi-natural habitats (= 100%). Using passive acoustic monitoring, we identified species-specific ranges of ambient temperature for early-winter activity, with overall median values around 15 °C. Historical climate data revealed a significant warming trend in December temperatures for our study region, equivalent to +0.6 °C per decade (p = 0.03), while bias-corrected projections under a +1.5 °C scenario predicted further warming. Early-winter bat activity was significantly higher in olive groves surrounded by less than 30% SNH cover, possibly due to increased foraging within groves when alternative habitats were limited. Rising winter temperatures may disrupt hibernation in bats, increasing fat depletion and mortality risk, especially where hibernacula and insect prey are scarce. Such disruptions may compromise the pest control services bats provide in agricultural systems. Structurally complex and diverse agroecological landscapes may buffer these risks by offering thermally stable habitats and food sources throughout winter. Our findings provide novel insights into early-winter bat ecology in Mediterranean farmland and suggest that even mild winter conditions can elicit flight activity across multiple bat species. Understanding how temperature and landscape structure influence bat activity during winter is crucial for developing conservation strategies in agroecosystems under climate warming. • Winter bat activity occurred from 7 °C, with a median threshold of 15 °C • Bat activity was higher in olive groves with <30% semi-natural habitat cover • Since 1981, December temperatures increased by +0.06 °C/year in the study area • +1.5°C warming may further disrupt bat hibernation and weaken pest control services • Diverse agroecological habitats may buffer climate impacts on bats and their services