Our smallest and most common bat is the Pipistrelle. These are essentially bats of buildings and can be seen at dusk in the centre of Norwich, in the towns, villages and countryside throughout the county. In the summertime all pregnant female bats form maternity colonies, where they produce a single baby. Pipistrelles choose chalet bungalows, houses ancient and modern as well as the more traditional sites of churches and barns. These breeding colonies usually form in May or June, the young being born in July and the mothers and adolescent offspring begin to disperse when the babies are weaned by the end of August subject to the prevailing summer weather conditions. The largest reported colony in recent years was 700 in the Waveney valley, but an average sized group these days (away from the broads and river valleys with their extra abundance of flying insect food) is 30 70. This sized colony could fit into a space not much larger than a house brick and crevices and spaces in brickwork or roof timbers are where they prefer to be. It is most unusual in East Anglia to actually be able to see Pipistrelles where they are hiding during daylight hours even with the aid of a torch in a roof space. Hibernation for Pipistrelles does not start in earnest until Christmas when the weather really starts to get frosty. They will not normally be present in their summertime haunts, but will be deep into the brickwork or flints of old barns and churches or behind loose plaster or deep in cracked timber, wherever there is a constant cool temperature and high humidity. Timber treatment, re roofing, house extensions and renovations as well as frightened or concerned householders and church authorities generate over one hundred enquiries locally each year which “English Nature” and the Norfolk and Suffolk Bat Group members deal with, helping people with bat problems, and occasionally vice versa !
Recent work has suggested that the bat we still call the “common pipistrelle” should be split into two species. The reason for this is that some bats call at about 45 KHz and others at about 55 KHz. There also seem to be slightly differences in face colour and behaviour. However, if you do not own a detector it really is rather difficult to distinguish the two sorts apart!
There is still an enormous amount to learn about the habits and distribution of these understudied and misunderstood animals and everyone is encouraged to help with this task by reporting any found or seen, and to encourage the conservation of known roosting sites.