Flittermice by John Mounsey

Is ‘flittermouse’ a northern English name for a bat, or is it more widespread? I had always thought that the word derived from the German ‘fledermaus’, but it seems that it is much more likely to be from ‘flytjamứs’, the old Norse name, which like so many other Norse words has hung on in this part of England.
Worldwide there are about 900 species of bats, ranging from fruit-eaters weighing over a kilogram with a wingspan of about 2 metres to tiny 2gm insect eaters. Perhaps because they are nearly all nocturnal they have often been associated with magic and the black arts (how else could they navigate in pitch darkness?); and their reputation was not enhanced by the discovery of the South American blood-sucking vampires. However, we now know that in this country they all find their way and locate their insect prey by echo-location, a very high pitched sound equivalent of radar, and none are blood-suckers! In fact they are all entirely harmless to man.


We have about 17 species of bat in Britain, thinning out as you go northwards, and as with birds they tend to specialise. Noctules are very like swifts with long wings and rapid, high flight, from which they may dive spectacularly to catch a beetle or moth. They usually fly over open country such as our riverside fields when hunting and have loud ‘voices’ to detect their prey at a distance. It is interesting that at least some moths can hear the echo-location system at work and drop out of the sky to avoid capture. By contrast, brown long-eared bats only seem to whisper as they hover among leafy branches on their relatively short broad wings, and this enables them to pick unsuspecting insects from tree flowers or leaves, perhaps along the edge of Akay Wood. Daubenton’s bat specialises in aquatic insects like caddis flies, usually cruising back and forth just above calm water like the Clews and often skimming pond skaters off the surface.
Like so many other wild animals and plants, most species of bats in Britain have declined in numbers over recent decades, partly because their insect prey have also declined, but often because their homes have been destroyed: old hollow trees and holes in the stonework of bridges. But at least one species has thrived; pipistrelles seem to have taken to modern domestic buildings enthusiastically, being small enough to squeeze through gaps only 10mm wide, perhaps between roof soffit and the house wall into the boxed-in eaves. They may also use the space between roof slates and roofing felt, but they will often move around to find a place where the temperature suits them if the weather changes. There are commonly between 50 and 150 pipistrelles in a summer roost, but usually the house owner is quite unaware of them. Marked bats have been weighed as they were caught leaving home for a night’s feed and again on their return, and have been found to have eaten up to a quarter of their own body weight of insects in one night. For a colony of 150 bats that adds up to an awful lot of insects!