![]() ![]() Although these sites may attract flying and non-flying predators and become high-risk areas, studies on predation of bats from this perspective are very limited. Since bats and their roosts are protected by European legislation, large aggregations of bats are often found in protected sites. Nonetheless, large aggregations of bats may provide a viable resource for predators (e.g., raptors and owls) and may even become the dominant prey, comprising up to 39 % of the diet of individual predators (Julian and Altringham 1994 Lesinski et al. Indeed, bats usually consist of less than 1 % of the prey of owls (Ruprecht 1979 Mikkola 1983 Kasprzyk et al. Since bats are very fast in flight, predation pressure on bat populations is likely to be a minor cause of mortality. Predation is considered a nearly universal pressure affecting individual animals and has, through evolutionary history, shaped the morphology, behavior and life history traits of prey species. From these results we tentatively conclude that predation is not incidental and that wood mice actively search for and kill hibernating bats or scavenge for weakened individuals. The highest predation risk occurred near the entrance of bunkers. The size of a hibernaculum and the population density of its bats had an effect on predation-dependent mortality. The years with high wood mouse predation pressure were characterized by a long frost period and a low mast production of common oak in the preceding autumn. The annual mortality (relative to the maximum winter population size) caused by wood mouse predation varied between 0.1 and 8.8 %, with a maximum local effect of 83.6 %. Predation pressure seemed to vary between winters, with a peak in the winters of 2004, 20. Trail camera surveys showed that wood mice actively searched for bats. Their remains showed a typical pattern of lesions consistent with those caused by predation by the wood mouse ( Apodemus sylvaticus). Most bat remains were found in December and January, with a second peak in April. During the winters of 2003–2015, we found 214 dead bats in 12 hibernacula in The Netherlands province of Zuid-Holland. ![]() ![]() In order to protect hibernating bats effectively, more knowledge about mortality factors is needed. Bat hibernacula with high numbers of bats can become high-risk areas, as they attract flying and non-flying predators. ![]()
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