Bats in Durham
Eleven species of bats are found in County Durham, of which eight are known to breed.
Common pipistrelles (Pipistrellus pipistrellus) (45kHz) are widespread, often found in modern housing estates.
Soprano pipistrelles (Pipistrellus pygmaeus) (55kHz) are known to occur on the Tees, Wear and Derwent, so are probably also widespread.
This photo shows a Brown Long-eared bat, which are often present in woodland. Although they are Britains second most common bats they are often missed because their calls are much quieter than other bats.
Nathusius pipistrelle (below 39kHz) have been observed at a number of wetland sites across the county but, as yet, we have found no nursery roosts.
Noctules are reasonably widespread and associated with mature woodland.
We had three reports of Leisler's Bats, all from Teesdale in late summer. This corresponds with dispersal from breeding roosts. The nearest known breeding colonies are in Sheffield, so this is a species to watch for as it may be expanding its breeding range.
Two unverified reports of Serotine Bats from Teesdale in late summer. again coinciding with post-breeding dispersal.
Brown Long-eared Bats are reasonably widespread but localised. They require large undisturbed roof spaces within flying distance of suitable woodland feeding.
Whiskered Bats are also reasonably widespread but localised. This is an important species in Durham as few roosts are known in Southern England.
Brandts Bat is much rarer here than Whiskered bats and our few roosts are of national importance.
Alcathoe's Bat has been identified fron Yorkshire but is extremely difficult to separate from Whiskered and Brandt's Bats. It may well be present in Durham but has yet to be identified
Natterer's Bat can be a hard bat to study because of its quiet echolocation calls, but is one of our rarer species. It roosts in trees and large undisturbed buildings where it can fly to warm up before venturing outside.
Daubenton's Bat is very widespread along the middle reaches of all our rivers. Most bridges on suitable waterways seem to support colonies. A thrilling sight on a warm summer evening!
Common and Soprano Pipistrelles
Until 1999, it was thought that there was only one native species of pipistrelle in Britain. With improvements in detectors it was found that there were in fact two distinct species that echo-located at different frequencies.
The common pipistrelle has a peak near 45kHz, and the soprano pip about 55kHz.
Some detectors aren't well enough calibrated to be certain which type you are picking up. However if you are tuned in and picking up common pipistrelles, and keep your detector at the same tuning, a soprano pip will produce a bird-like cheeping sound.
P. Nathusii is common on the continent but was not discovered in Britain until 1998 when the first colonies were found in Lincolnshire and Northern Ireland. Its call is at a lower frequency than common pip, at about 37kHz. Ian Bond says: "I've always been a bit dubious about certain records that purport to distinguish between the other two Pipistrelle species, the Common and the Soprano, so I thought that it would be equally unclear whether we were hearing Common or Nathusius'; however the peak frequency really was quite distinct at 37/38kHz (and increasingly tinny above 40kHz) and they seemed to be putting more energy in to the calls compared to other Pips."
Updated Feb 2015