The Common noctule (Nyctalus noctula) is an insectivorous bat that is widespread throughout Europe, Asia, and North Africa. These bats hibernate in large groups and females migrate during early pregnancy to return to their natal maternity colonies and give birth to their pups.
The Common noctule has a short fur that becomes dark brown after moulting in June (males) or July/August (females); later it changes to red-brown before the onset of winter. When awake, the body temperature is 36.5 °C (97.7 °F) but it decreases significantly during inactivity.
Common noctules are found in most parts of Europe, central Russia, across the Ural mountain, Caucasus, Turkey, the Near East, to southwestern parts of Siberia, the Himalayas, China, Malaysia, Taiwan, and Japan. These bats prefer small to medium-sized woodlands but also forage up to 20 km (12 mi) away from the woodland at night. They also hunt over wetlands and pastures. During the day they roost in tree holes or even bat boxes attached to tree trunks. During winter they hibernate in caves, rock crevices, bat boxes, or blocks of flats in Eastern Europe, where they are the most common hibernating bat species in the cities.
Common noctules are migrating but only the females migrate between the breeding area and hibernation range. Males do not migrate but scatter along the females' migration routes to have higher chances of attracting the first females migrating back to the wintering regions. Common noctules are social animals that hibernate and breed in colonies. However, during the summer, males become solitary or form small bachelor groups. Common noctules hibernate in winter and sometimes gather in hibernation colonies of up to 1000 individuals. In late summer the adult females migrate back southwards to the wintering areas and the young follow them later. At the beginning of winter, usually in November (but this is strongly dependent on the ambient temperatures), Common noctules start to hibernate in large groups with both sexes in the same roost. Sometimes summer territories and hibernating places are hundreds of kilometres apart. Common noctules start their hunting in the early dusk. They fly high above the forested areas reaching speeds of up to 50 km/h (31 mph). Because of the temporally limited availability of insect prey, they have short daily activity periods before sunrise and after sunset of in total one hour or less and so must cope with up to twenty-three hours of fasting a day.
Common noctules are carnivores (insectivores). Their diet mainly includes beetles, moths, and winged ants.
Common noctules mate in late summer in the wintering areas, and the females delay implantation during hibernation until spring. In early autumn, males attract females with singing calls. In the harem roosts, males often do not enter torpor, but stay awake and mobile to defend the females from other males. During early pregnancy in late April, the females migrate north, as far as the Baltic region, to return to their natal maternity colonies and give birth after being pregnant for 6-8 weeks. Each female rears 1 or 2 pups per year. At birth, the young is about a third of the maternal body weight, and after 3 to 4 weeks of suckling, it leaves the roost almost fully developed.
There are no major threats to this species at present. However, locally Common noctules suffer from the loss of trees that they use for roosting.
According to the IUCN Red List, the Common noctule is common throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List.
