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

Abstract

a b s t r a c tClimatic 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.

Summer temperature and precipitation govern bat diversity at northern latitudes in Norway

“…The important effect of temperature on diversity as found in this study was highly anticipated based on general theories on bat distribution (Kaufman andWillig 1998, Ulrich et al 2007, see also Michaelsen et al 2011). However, common occurrence of northern bats in alpine habitats and the relatively wide distribution of other species were not expected.…”

“…Moreover, all areas studied have tall mountains blocking out the sun well before sunset and after sunrise. This factor can influence bat distribution and behaviour at these latitudes (Michaelsen et al 2011). Available publications from the study area (Gjerde and Fuszara 1995, Olsen 1996, Michaelsen 2003, 2012, 2004a,b, Michaelsen and van der Kooij 2006, Isaksen et al 2009 suggest that bats can be found in all available landscapes and habitats, ranging from alpine areas to coastal plains with only bracken vegetation, cliffs, cities, roads (street lamps), cultivated areas, freshwater and marine shores, woodlands (all sorts), coastal islands and more.…”

“…During summer, most species and the highest densities are found close to freshwater and other water sources with low salinity in the warmest parts of the landscape (Michaelsen 2012). At least some species seem to avoid open habitats (Michaelsen et al 2011). Most efforts in mapping bats stem from lowland areas, but altitudinal records suggest that at least northern bats occasionally can be found up to about 900 m.a.s.l.…”

“…Bat diversity is negatively correlated with latitude, a surrogate factor for temperature and light conditions (Kaufman and Willig 1998, Ulrich et al 2007, Michaelsen et al 2011). In northern Europe, both summer and winter temperatures drop with latitude, the duration of summer shortens, and the length of summer nights decreases and is finally void.…”

“…For a given latitude, temperature varies with several factors, the most obvious being altitude (Schönwiese andRapp 1997, Moen 1999). Although altitude itself can be a significant explanatory factor of both local distribution and reproduction (e.g., Stutz 1989, Syvertsen et al 1995, Cryan et al 2000, Russo 2002, Kanuch andKristin 2006, Michaelsen 2010), it can make no universal statement about bat distribution over wider areas (Michaelsen et al 2011).…”