Geoffroy's bat, Myotis emarginatus, preys preferentially on spiders in multistratified dense habitats: a study of foraging bats in the Mediterranean

In a Geoffroy’s bat Myotis emarginatus colony in central Iberia, we investigated the foraging behaviour of six lactating females by means of radio-tracking and the diet of 23 individuals by faecal analysis. The bats preferred to forage mainly in pine plantations, riparian woodland, and scrubland, whereas native dehesa (a loose semi-natural oak Quercus rotundifolia and Q. suber woodland) was not exploited as expected. By far the most important prey type for this bat in the Mediterranean were spiders. We conclude that Geoffroy’s bat prefers to forage in multistratified dense habitats, even if these include nonnative plantations. The vertical structuring and especially high cover, along with the combination of both parameters are important for this highly manoeuvrable, clutter-tolerant bat. This is valid even when the vertical component is much reduced as occurs in scrubland, in the first succession steps to woodland creation, and in degraded conditions. Under such circumstances, aerial weaving spiders might be detected and captured when lying in their webs. It is likely that dehesa is too loosely wooded to offer suitable characteristics for orb-weaving aerial spiders to build webs, and thus it may not be as attractive for M. emarginatus as more dense habitats.