Spatial and temporal variability of bat foraging in a western European low mountain range forest

Abstract

We monitored echolocation calls to measure the flight and foraging activity of European bats at twenty-four locations in the Palatinate Forest, Germany. Bats' flight activities correlated with their foraging activities at different sites. The distribution of bat foraging sites may be patchy even in a continuous forest habitat. Pipistrelle bats changed some of their foraging patches during the summer-season, most probably due to temporal differences of the resource densities at those patches. Daubenton's bats in contrast showed steadily high activities at two investigated forest lakes. The feeding buzz rate declined during five hours of nightly bat foraging. The nocturnal bat activity did not change significantly during this time, with the exception of few patches. Food resources as well as additional factors, like acoustical landmarks that enable orienting of echolocating bats, and habitat features that allow special foraging strategies should influence the quality of patches and their use by bats. The use of one, or of different foraging patches during the year, may depend on the seasonal constancy or variability of resources, on the degree of isolation of a patch type, and on the species specific foraging strategy.