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. Geoff Billington recorded Nathusius pipistrelle (below 39kHz) over the Tees at Cotherstone and near Bowes. We have watched at least four on more than one occasion over the lake at Whitworth Hall. However, we have not been able to find them elsewhere in the county.
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.
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 spaces 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 recently 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 pip. 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.
Nathusius Pipistrelle
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.
It has an echolocation peak at about 37kHz - make sure your bat detector is correctly
calibrated!