Topography is a limiting distributional factor in the soprano pipistrelle at its latitudinal extreme

Abstract

Climatic conditions such as temperature and seasonality are becoming increasingly harsh towards the latitudinal extreme of the distribution and may limit the occurrence of mammals through decreased food availability or accessibility. For nocturnal bats increasing day length in summer may also limit the range latitudinally. We investigated the effect of long term mean temperature, precipitation, altitude, water affinity, terrestrial habitat, and topography on the summer distribution of the soprano pipistrelle Pipistrellus pygmaeus at its northern limit in western Norway (62°N, 06′E) in a fiord landscape. We recorded presence/absence of the species in 138 sites by means of ultrasound detectors (and an acoustic lure). A binary logistic regression analysis showed that temperature is significant in predicting occurrence of soprano pipistrelles, with no animals in areas of less than 13 °C (long term mean July temperature). Further, the model suggests that the species prefers areas where steep mountains to the north shade out the sun before sunset and after sunrise. Here soprano pipistrelles can start hunting up to 2 h earlier than in a flat landscape, thus spending more time on energy consumption.