Any structure is a potential bat roost, providing there is sufficient access – bats need only a 20mm gap.
There are 17 species of bats in the UK and some populations are starting to stabilise after huge losses in the last century but there is still a long way to go before we make up for the severe declines, according to the Bat Conservation Trust. The most rare is the greater mouse-eared bat and it is thought that we have just one left in the UK.
Pipistrelles, the species most often found roosting in houses, often choose modern houses and like tight spaces, usually roosting behind barge boards or hanging tiles, or between underfelt and tiles, and sometimes behind window frames. You may see droppings on windows, walls or sills in summer, or you may see no sign at all.
Check droppings by doing a roll test between your finger and thumb – if it feels hard then you probably have mice not bats. A bat dropping will crumble to dust quite easily because it consists of indigestible insect parts. Bat droppings present no significant health hazard in the UK, and can be swept up to use as fertiliser for the garden.
You will see most bats at dusk as they come out to feed. A clue is the chattering sound that bats may make at dusk just before they fly out to feed. In July and August they are particularly vocal around dawn, when hungry babies call to mothers as they return from their night’s insect hunting.
Long-eared bats prefer older buildings, and usually roost inside the roof void adjacent to the timbers, often along the ridge or adjacent to the chimney breast. Their droppings are more easily seen, often in a line under the ridge, but these bats come out after dark and so are harder to spot.
Bats are not rodents, and do not nibble or gnaw wood, wires or insulation. They do not build nests, nor do they bring bedding material or insect prey into their roost. Bats are clean and sociable animals.
A bat flying in a room has most likely taken a wrong turn and is looking for a way out. Close the door, open the windows as widely as possible, draw back the curtains and remove anything that obstructs the window opening. Dim the lights and give the bat the chance to find its own way out. Bats navigate by sending out high-pitched sounds and listening for the echoes, so the bat should soon find its way out of the room.