Nyctalus Bats

Leisler’s Bat (Bat of the year 2026-27 by BatLife Europe)

Nyctalus leisleri

Description and identification

Leisler’s bat is a medium sized British bat, dark brown in colour with rounded ears and nose. It has a fur mane around its shoulders, which can stand on end when it is agitated. Whilst the lower parts of its fur are dark brown, the tips are reddish, making it look glossy. The Leisler’s bat has long, narrow wings and hairy forearms / under wing, giving it the name of the ‘hairy-armed bat’. At first glance a Leisler’s bat looks like a noctule, but smaller.

The echolocation calls of Leisler’s bat can be difficult to distinguish from both noctule and serotine. The calls range from 15-45 kHz, peaking at 25 kHz, making a chip-chop call characteristic of the two UK Nyctalus species, but are less harsh sounding than the noctule. Like the noctule, Leisler’s bat calls are very loud and can sometimes be heard from some distance with a bat detector.

Status and distribution

Leisler’s bats are found throughout most of the UK but are rare; they are more common in Ireland. In England they are mainly found in the central and southern counties. There appear to be several Leisler’s bat colonies in the Sherwood Forest and Dukeries areas of Nottinghamshire, and those in the bat box schemes there attract bat enthusiasts from far and wide! Away from these core Nottinghamshire areas it is found less frequently but has a widespread distribution.

Roosts

Leisler’s bats are naturally a woodland species, with maternity colonies occupying tree holes, cracks and crevices. They are regularly found in bat box schemes at Sherwod Forest Center Parcs, Clumber Park and Budby Heath. Maternity roosts have been found in boxes at Budby and by the Forestry Commission in Elkesley Wood. Less commonly, Leisler’s bats roost in buildings, where they roost in similar positions to other crevice-dwelling bats, under tiles, roof felt or in crevices in gable ends. In Nottinghamshire, Leisler’s bat roosts have been recorded in at least three attics, a tree, a church tower and in bat boxes.

Leisler’s bats will continue to roost in trees in winter but can also be found in cavities in buildings and occasionally in caves and tunnels, although none have been found in Nottinghamshire yet.

Food and foraging

Leisler’s bats hunt in a range of habitat types including cattle/sheep pasture, woodland, rivers, lakes and canals. They fly quite high, between 10m and 70m and swoop to catch larger prey. They also hunt around streetlights and floodlights for insects that are attracted to the light. Prey is caught and consumed in flight.

The diet of the Leisler’s bat has been investigated in Ireland, England and Germany48 where it was found that the bats eat mainly medium-sized and small insects, particularly moths and those with aquatic larvae such as caddis flies. Dung flies make up a significant part of their diet at certain times of the year.

Despite their relatively large size, Leisler’s bats will also eat much smaller swarming insects like midges and there is evidence to show that one feeding method used is to fly through swarms, filter feeding.

Click below to play a video with time exspanded and heterodyne bat echo location calls.

Noctule Bat (Bat of the year 2016-17 by BatLife Europe)

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 stable.

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.

Conservation

Protected in the UK under the Wildlife and Countryside Act, 1981. Priority Species under the UK Post-2010 Biodiversity Framework. European Protected Species under Annex IV of the European Habitats Directive.

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.

Click below to play a video with time exspanded and heterodyne bat echo location calls.