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Nyctalus noctula

Description and identification

The noctule is the largest bat in the UK and can often be seen flying high and straight in the open soon after dusk. It is a powerful flyer and often one of the first bats to emerge. Its long, slender wings mean that it is built for speed rather than agility, much like the jumbo jet of the bat world. The noctule is a golden colour, with large rounded ears and a uniformly coloured face. The short back fur is a golden red-brown whilst the stomach is slightly lighter in colour and less shiny.

The noctule calls at around 20 kHz, although this ranges from 17 – 29 kHz depending upon what the bat is doing and the environment it is in. The loud, low frequency of a noctule call means that some people (especially children) can hear them without a bat detector. On a heterodyne bat detector, a noctule echolocation call makes a ‘chip-chop’ sound.

Status and distribution

The noctule is widespread in England and Wales, absent from northern Scotland and all of Ireland. It has suffered declines and is now absent from some highly agricultural areas where the meadows they use for feeding have been lost41. The population of noctules in Great Britain is currently considered to be stable42.

In Nottinghamshire, it is common and widespread and has been recorded in 33 hectads since 2010. However, it should also be noted that the loud noctule can be ‘over-recorded’ because it can be detected at distances beyond those of most other UK bats.

Roosts

Noctules are generally tree dwellers but will also use bat boxes. They will use holes in trees and have a preference for old woodpecker holes, both in the summer and in autumn. The bats form mixed sex colonies in spring, before the females group together in maternity colonies. Females give birth to a single pup in June or July and will use a network of trees, switching roosts fairly regularly and taking their young with them.

In autumn, male bats will hold a territory in a hole in a tree (or maybe a bat box!) and will try to attract females to mate by using shrill calls (song) and a strong odour. Noctules normally spend the winter in larger tree cavities where they hibernate individually or in small groups, but are also known to utilise smaller cracks and crevices. They will also migrate long distances.

Noctule roosts have been found in trees at six sites in Nottinghamshire and they are also regular visitors to many of the bat boxes monitored by NBG in woodland to the north of the county, where they have been known to share a box with Leisler’s bats.

Food and foraging

Noctules favour large moths, mayflies and beetles; notably dung beetles and cockchafers, which they can devour easily with their powerful jaws and very sharp teeth. They feed mainly over meadows, grasslands and ponds, and they utilise woodland edges and hedgerows where insects congregate. Foraging noctules can be seen flying in a straight line in the open, making sudden swoops and dives to chase after prey.

The noctule can fly at over 50 km/h and is known to fly several hundred metres43 up, however it is normally found flying lower at 10-50m above ground level. Flying at this height, and its foraging and migration strategy, means that the noctule is particularly vulnerable to impacts from wind turbines.