A medium-sized bat with a wingspan of 250 to 300 mm and weighing up to 12 g.
Similar at first glance to Daubenton’s bat, the Natterer’s bat has a distinctive white belly which can sometimes be seen as the bat flies slowly at roof height soon after
sunset. The margin between the dark dorsal fur and the pale belly is unusually sharp, compared to other bat species. The
broad, pointed wings may be seen against a light sky. Closer, it may be possible to see that the bat flies with its tail pointing down, instead of backwards. Seen in the hand, Natterer’s bats have sandy grey fur on their back, the face is pink, as are the limbs, the long ears curve backwards at the top and are darker at the tip than at the base. The tail membrane has a characteristic fringe of short hairs which may be used in capture of its invertebrate
Natterer’s bats use short, frequency modulation, echolocation calls, strongest at about 50 kHz, often repeated rapidly, but faintly. The sound of their calls on a
heterodyne detector has been likened to the noise of burning stubble.
Natalie the Natterer was a firm
favourite with visitors to the Penzance Bat Hospital in the 1990s. She was found on the ground by pupils at Manaccan School and was probably suffering from pesticide poisoning. Although she was treated and recovered she was never able to fly well enough to be released, but remained at the Bat Hospital for 10 years where her presence supported their education and research.
© Paul McNie
Natterer’s bats generally roost in old stone buildings, favouring gaps in stonework and behind wooden beams, although they also use tree holes and crevices. Relatively few roosts have been identified. Winter roosts are used from December onwards and are usually underground sites including caves, tunnels and mine workings. Natterer’s bats tend to be found singly, or in small groups, in the cooler parts of the hibernation sites, sometimes in association with Daubenton’s bats.
Like many bat species, Natterer’s favour woodland, hedgerows and grassland, often close to water. Natterer’s bats emerge once the sky is dark and return to the roost an hour or more before sunrise. Radio tracking studies have shown that colonies have exclusive summer home ranges and bats’ feeding areas do not overlap with those of other Natterer’s colonies. Natterer’s bats hunt unusually close to vegetation and have been shown to catch a large proportion of their prey from surfaces by gleaning. Evidence for this is that much of the bat’s prey consists of day-flying insects which would be resting when the bat is flying.
Maternity colonies of up to 200 females, and the occasional interloping male, assemble in the early summer, with the pups born in late June or early July. Adult males roost individually, or in small groups, often close to the maternity colony and frequently move between roosts. In late summer and early autumn swarms of Natterer’s bats may occur near the entrance to their hibernation sites. This behaviour is thought to be connected to mating activity and swarms include individuals from several summer colonies.
Tracks and Trails:
Natterer’s bat is difficult to discriminate from other British bats using only a bat detector, its quiet call is similar to that of other Myotis bats and the brown long-eared bat.
Did you know?:
Nothing to do with gossip, Natterer’s bats are named after the 19th Century
Austrian naturalist Johann Natterer who spent 18 years exploring in South
America. Natterer’s bat is also known as the red-armed bat because of its pinkish-brown arms.
The UK population of Natterer’s bat is internationally important and surveys by the Bat Conservation Trust indicate that the population is increasing. Worldwide it is regarded as not being at risk of extinction, but in common with many bat species it is under threat from loss of habitat, food sources and roost sites.
Natterer’s bat is recorded from sites across Cornwall, with a central and western bias. Analysis of records by the Cornwall Bat Group indicate that numbers may be declining, against a positive national trend. It is found throughout the UK and Ireland. Natterer’s bat occurs
across Western Europe and possibly, discontinuously, as far east as Japan.
Monitoring of summer maternity roosts and hibernation roosts by licensed bat
workers. Mist net trapping by licensed bat workers. Emergence surveys. Bat detector monitoring. Cat kills and incidental reports.