Riparian bats temporally partition foraging at the cold edge of an upslope climate-driven range expansion

Abstract

Climate change is driving many species to shift their distributions polewards and upslope, exposing populations to the challenging abiotic and biotic conditions of the range’s cold edges. At these limits, resources are often scarce and competition, including among conspecifics, can be intense. Long-term monitoring of the riparian bat Myotis daubentonii, a species that shows altitudinal sexual segregation, has revealed an upslope shift of reproductive females within a central Italian river system, from a historical limit of about 850 m a.s.l. to about 1050 m a.s.l. Here, we investigated whether females colonising these newly suitable high-elevation habitats adjust their foraging behaviour in ways that reduce competition. We radio-tracked 14 reproductive females sharing maternity roosts in the cold-edge zone and analysed the spatial and temporal distribution of their foraging activity. All females showed pronounced temporal segregation in their use of foraging areas and regardless of roost membership. Spatial overlap tended to be greater among tracked roost mates, but this trend was not statistically significant. These findings suggest that fine-scale temporal niche partitioning limits interference and promotes efficient use of limited resources at the cold edge. Strong fidelity to individual foraging sites further indicates that site familiarity may buffer competition and reduce foraging costs. Variation in commuting distances among individuals suggests diverse foraging strategies, plausibly reflecting differences in competitive ability or reproductive state. Our results show that at newly colonised cold edges, female M. daubentonii exhibit behavioural plasticity facilitating coexistence among conspecifics and enhancing persistence in suboptimal habitats under climate change.