© Hugh Clark and the Bat Conservation Trust.
All of the 15 species of bats found in the UK depend on trees and woodlands to some extent.
The importance of trees to bats varies with the species, season and foraging behaviour. Some species of bats rely exclusively on trees for roost sites; others use them for only part of the year. The most tree-dependent bat is the Noctule. It roosts almost exclusively in trees, using hollows, cracks and old woodpecker holes.
The bat year starts about March when they wake from hibernation. They are then active throughout the summer nights, feeding on insects and building up their energy as fat reserves to last through the winter. In the autumn, they move to the winter hibernation sites and gradually become drowsy and then enter into their full winter sleep.
Where bats are roosting in trees, the wood around the entrance hole may be stained by their droppings or oil from their fur. On warm summer days, they can sometimes be heard squeaking in the roost and there may be a sharp acrid smell too.
Under the Wildlife and Countryside Act, it is an offence to intentionally kill, disturb or handle bats. It is also an offence to destroy any structure that they use as a roost, whether or not bats are occupying it at the time. If work must be carried out on a tree bats use, the relevant statutory nature conservation organisation must be informed.
For many years it was said that native broadleaves were the most important trees for bats but recent work suggests that the greatest density of bats hunting in woodland is on rides with plenty of conifers.
Bat boxes may be used by some species in summer. Often three boxes are put up on the same tree trunk, each facing in a different direction as the bats like to move from one box to another if one gets too hot or too cold on a sunny day for example.
More: Further information on bats is available from the Bat Conservation Trust who publish Bats in Trees.
See "Bat Workers Manual" (2005) JNCC