It is largely a resident species and the summer roosts and winter hibernation sites are usually within of each other. Behaviour Natterer's bat is nocturnal and insectivorous. It emerges at dusk to hunt for insects and uses echolocation to find prey and orient itself at night. Like many other species of bat, it emits sounds at too high a frequency for most humans to detect and then interprets the echoes created in order to build a "sound picture" of its surroundings. The frequencies used by this bat species for echolocation lie between 23 and 115 kHz and have most energy at 53 kHz. The individual signals have an average duration of 3.8 ms. The wide bandwidth of its frequency-modulated search signals enables it to detect prey only a few centimetres from vegetation and it does not use vision, olfaction or sounds emitted by its prey for this purpose. The bat feeds on the wing and it mostly catches insects in flight but it is also able to feed on prey items such as spiders and caterpillars dangling close to foliage on silken threads. During a study of the bat's diet, examination of droppings showed that it can also gather prey items from the ground. The diet was found mostly to consist of large Diptera (flies) but Trichoptera (caddisfly), Hymenoptera (bees, wasps, ants and hoverflies) and Arachnida (spiders and harvestmen) were also commonly eaten. The remains of other prey items occasionally found in the droppings included Lepidoptera (moths), Coleoptera (beetles), Hemiptera (bugs), Dermaptera (earwigs) and Chilopoda (centipedes). This bat may use its interfemoral membrane to catch prey and the fringing hairs may have a sensory function. It has been shown that it can land on the ground to pick up and pursue invertebrates that are active at night, and continues to emit search signals in order to locate them precisely. Breeding takes place in the spring and many Natterer's bats may congregate in a nursery roost. After fertilisation, a female normally gives birth to a single offspring after a gestation period of fifty to sixty days, but twins sometimes occur. Weaning takes place six or seven weeks later and the juvenile becomes sexually mature the following year. Status The IUCN has listed the Natterer's bat in its Red List of Threatened Species as being of "Least Concern" because it has a very wide distribution and is abundant in many parts of