Predation of wood mice (Apodemus sylvaticus) on hibernating bats
1. Animal Ecology and Physiology Group, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, The Netherlands
2. Apeldoorn, The Netherlands
Bat hibernacula with high numbers of bats can become high-risk areas, as
they attract flying and non-flying predators. In order to protect
hibernating bats effectively, more knowledge about mortality factors is
needed. During the winters of 2003–2015, we found 214 dead bats in 12
hibernacula in The Netherlands province of Zuid-Holland. Most bat
remains were found in December and January, with a second peak in April.
Their remains showed a typical pattern of lesions consistent with those
caused by predation by the wood mouse (Apodemus sylvaticus).
Trail camera surveys showed that wood mice actively searched for bats.
Predation pressure seemed to vary between winters, with a peak in the
winters of 2004, 2011 and 2015. 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 %. 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 size of a hibernaculum and the population density of its
bats had an effect on predation-dependent mortality. The highest
predation risk occurred near the entrance of bunkers. 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