Are bats roosting on your development site?

If you’re a land or housing developer, it can be frustrating to find bats roosting on your site, or within buildings you plan to develop. All eighteen bat species known in the UK, are legally protected. You must not kill, injure, or disturb them, or their empty roosts.

So, what do you do?

In this article, we’ll explain how, and where, bats like to roost. We’ll also explain what you need to do regarding bats, whether they’re present on your development site, or not. And if they are on your site, we’ll highlight the likely mitigation measures required to gain planning permission.

Bats roost in many places

Bats can be found roosting in buildings, trees, cellars, under bridges, and in tunnels. In fact, any structure that offers potential cavities and crevices to use. Different species of bat have different roosting requirements, and they can be incredibly hard to spot. You might not know there are bats on your site as they’re often hidden from view.

Given that bats hibernate during the winter months, their activity is far more visible during the summer.

Bats roosting or not, you might well need a survey

The protective laws surrounding bats are classified as “strict liability”. This means, there’s no excuse for unforeseen harm – you must have investigated thoroughly. Most planning authorities will, therefore, request a survey if your site could provide any habitat at all for potential roosts. This could include trees or woodland, existing structures such as barns and buildings, or potential underground habitat.

Carried out by a licensed ecologist, a stage one survey (often called a Preliminary Roost Appraisal or Daytime Bat Assessment) looks for potential roosting opportunities for bats, such as gaps and crevices. The ecologist will also look for evidence of bats, such as droppings in a loft.

Should there be any potential for bat roosting or evidence of actual bat presence, further surveys will be necessary. These must be undertaken at night, from May to September. The ecologist will confirm whether bats are roosting and gain further insight on the roost and species. It’s also important to estimate the number of bats present.

This information will help to determine what proportional mitigation or compensation measures are required, to accompany a licence application to Natural England.

So, as we write this article in May, we enter prime bat survey season.

We help many developers through this process, reducing delays in their planning application. You can learn more by visiting our bat survey page.

Accommodating bats on your development site

The outcome of your surveys will determine what actions you need to take concerning bats. Planning and environmental rules require that development minimises the impact on natural habitats and maximises the benefits for biodiversity. This can be a tricky balance to achieve, but it is possible.

If bats are roosting on your site, the first consideration will be whether you can avoid disturbing them. You might be able to build in a way that leaves the roosting structure undisturbed.

If avoidance is not possible, you will be asked to undertake suitable mitigation measures. This might mean carrying out building work in the winter months when the bats are hibernating. Most importantly, you’ll need to try and protect the bat population.

Full and equivalent compensation is necessary when there are unavoidable adverse impacts on a bat roost. For example, if you have to demolish an old building. You must then create new roosts and protect any remaining roosting or resting places for bats. For example, this might include the provision of bat boxes on your site. All of this has to be formally approved under licence in advance.

Where to learn more

The more informed you are about bats roosting, and what your obligations are, the easier your planning application will be. There are many authoritative websites that provide information, such as:

Government guidance for bat surveys and mitigation for development projects

CIEEM: bat mitigation guidelines

Bat Conservation Trust: planning and development guidance

You can also speak directly to one of our expert ecologists. We’re helping many of our clients with bat issues on a regular basis. Please get in touch if you’d like to chat through your development project.