All Scottish bat species roost in trees to a greater or lesser extent. Often it is difficult to ascertain whether a tree may contain a bat roost. Roost holes may be high above ground level and difficult to see, especially in summer, when foliage can obscure the view.

Certain physical signs can help. For example, droppings below a roost entrance or smear marks at a tree hole. On a warm day "chittering" sounds can sometimes be heard from a roost.

Features used by bats include rotted-out holes, cracks and crevices, Some species of tree are more likely to offer suitable roost sites than others, for example Ash or old Oak trees often have suitable features, whereas most conifers do not. 

Tree roosts (left to right): 

Low crevice used by Brown Long-eared Bats (Plecotus auritus)

Hole 10m above ground level, used by Noctules (Nyctalus noctula)

Split in Ash trunk, containing Daubenton's Bats (Myotis daubentonii)

Generally, surveying trees for bat roosts is a three-part process:

1. An initial visual survey allows features with potential for roosting bats to be identified.

2. An emergence survey, using a bat detector at sunset or dawn on a night with suitable weather for bats shows the presence of a roost (providing it is occupied at the time). It also allows the surveyor to place the tree in the context of the bats commuting and foraging behaviour.

3. In some cases it may be necessary to use access equipment to examine features in trees. Usually an endoscope is used to look inside cracks and holes, for the presence of bats and for droppings and other signs.

All bat roosts have legal protection regardless of whether bats are present.

© David Dodds Ecology (2008)