Usage of buildings in the life cycle of two endangered Rhinolophus species in the Mediterranean region: implications for roost protection

Abstract

Synanthropic roosting may allow cave-dwelling bats to cope with habitat fragmentation provided that suitable buildings are sustainably protected. This study on Asinara Island, Sardinia, focuses on roost requirements in synanthropy at different life stages of two endangered bat species, Rhinolophus hipposideros and Rhinolophus ferrumequinum. We rated the roost potential of 532 buildings and compared it with actual roost usage. Microclimate was compared across different roost types and between species, and bat composition and behaviour in nurseries of R. hipposideros were related to roost structure and microclimate. The two species occupied 25% of structures rated as “high potential”, versus 5% and 0% rated as “intermediate” and “low potential”. Concerning microclimate, R. hipposideros preferred warmer and drier day roosts, with higher temperature fluctuations during summer, while winter, and night, roost microclimate was comparable between species. In larger, warmer, and drier nurseries, colony size and proportion of reproductive females were higher and parturition started earlier. Before parturition, roost temperatures were inversely correlated to clustering, supporting its thermoregulatory function. Mothers spent in total 50% of the night inside the nursery caring the pup. Roost microclimate, size, and location close to foraging areas may thus promote breeding success. We conclude that a structure-based rating of roost potential supplemented by species-specific microclimatic requirements constitutes a promising predictor of roost usage. Moreover, adequate buildings support the complete life cycle of R. hipposideros in the absence of suitable caves. Buildings thus deserve increased protection measures in fragmented Mediterranean landscapes to ensure sustainable bat conservation.