Bat Boxes: Some frequently asked questions

What type of box?

There are several types of boxes on the market each having a specific function. The considerations when choosing should be:

Where the box will be positioned e.g. on a tree trunk or the side of a building.
Which bat species is being encouraged. Some of the larger bats require more space and a larger box e.g. brown long-eared or noctule bats.
What time of year you are hoping to encourage bats. There are different boxes for summer bat roosts and winter hibernation roosts.

All wooden boxes should be constructed from preservative free wood. Bats are especially attracted to weathered boxes. Other types of boxes are made from a mixture of concrete and sawdust.

Where is the best place to position the box?

The simplest and cheapest method of fixing a bat box up is to nail the box to its mounting.
To increase the chance of it being used, locate the box at a site where bats are known to feed that is sheltered from strong winds and exposed to the sun.
Unlike birds and rodents, bats do not build nests. Warm roost temperatures are important, especially to pregnant females and their young.
Ideally, put up two or three boxes facing in different directions to provide a range of temperature conditions. For example: facing from south-east to south-west, so that the sun falls on the box for part of the day. During very hot days the south facing box may overheat, but the other boxes should have some shade during the day.
Bat boxes should be located close to a linear feature such as a treeline or hedgerow. Some bat species use these features for navigation between their roosting site and feeding ground and to avoid flying in open and exposed areas.

On trees

Height: Generally the higher the box is positioned the better (1.5 - 6m). Most species will use higher positioned boxes with the exception of brown long-eared bats, which prefer the box 1.5m above the ground.
If you are locating boxes in public areas consider the possibility of vandalism.

On buildings

Placing the boxes high up by the eaves on a building will reduce the likelihood of the bats falling prey to cats or humans.
As with trees the aspect of the box should capture sun for most of the day. North or northeasterly sited boxes will have little chance of being used as summer roosts because the box will not be warmed by the sun.

Other structures

Poles, gazebos, garden walls and sheds have been suggested. However, the main danger is that the boxes are not high enough off the ground and are too visible to predators.

How many boxes?

Two or three boxes will always be preferable to one, but a single box has a chance of being used, although this depends on the species that use the local area.
3 boxes per tree can be arranged around the trunk of larger trees. This is especially desirable in larger coniferous plantations.

How long before bats will use the box?

It may take several years for the bats to find the box. Be patient!
It is highly unlikely bats will shift their roost from a well-used site (e.g. in a roof) to a newly positioned box.
They may prefer weathered wood that mimics old trees rather than a brand new box.
There may be plenty of other suitable roosting sites in the area.

What other considerations are there?

Do not be tempted to open the box to check if it is being used (a special license is required in the UK to disturb roosting bats and to handle them). The bats may unintentionally be injured if the box is opened, for example by trapping their feet in the lid as it is closed.
To check if the box is being used, look out for droppings, urine staining, listen for 'chattering' and watch the box for an hour after sunset to observe any bats leaving to feed.

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