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Bitesize Guide to Bat Surveys

We’re now in the middle of the bat survey season and the good news is it’s not too late to begin new bat surveys if you haven’t yet got started. We’ve put together a short guide on how to navigate the process and minimise the impact these little creatures have on your development – and vice versa.

How are bats protected?

All 18 species of bat found in the UK are protected under European and domestic legislation against killing, injury or disturbance and it’s also a criminal offence to destroy or obstruct access to their roosts, even if bats are not present at the time. Failing to consider the impact of your activities on bats could result in very bad publicity for your company, a hefty fine and even a prison sentence, so it’s crucial to do things properly!

What are the different types of bat surveys and who needs them?

If your development plans include demolishing, re-roofing or significant renovation/reconfiguration of a building, particularly an older building, or felling/lopping a mature tree, it’s essential to consider the possibility that there are bats present. The first step is to commission a Preliminary Ecological Appraisal (PEA) or a Preliminary Roost Assessment (PRA). A PRA focuses only on bats (and nesting birds) and so is only appropriate for sites on which there is no real potential for other protected species. These phase 1 surveys will look at features of buildings and trees such as cracks and crevices, missing roof tiles and loft voids as well as any evidence that bats are present, such as droppings. Each building or tree will be assigned a level of suitability for bats: negligible, low, moderate, high or confirmed.

If there is negligible potential, no further surveys are required. In all other cases, you will need a Bat Presence/Absence Survey, also known as a Dusk Emergence / Dawn Re-entry Survey. These monitor the presence or likely absence of bats at dawn and/or dusk. If there are bats present, the report will identify the species (using echolocation sonogram analysis) and approximate numbers. Between 1 and 3 site visits will be required, depending on the level of suitability identified.

In some cases, where the initial assessment or environmental monitoring has shown conditions on the site to be suitable for hibernating bats, a Hibernation Survey may be required. For larger developments which could have an impact on bats’ foraging habitats, an Activity Survey may be required to assess how bats are using the site.

When should surveys be carried out?

It’s important to consider bats early on in project planning to avoid later delays.

The phase 1 PEA or PRA involves just one site visit and can be carried out at any time of year. A Presence/Absence Survey (or Dusk Emergence/Dawn Re-entry Survey) needs to be carried out during the active season of May – August/September. For low suitability buildings, just one site visit is normally required, during May-Aug. For medium suitability buildings, 2 visits are needed – of which at least one is during May-Aug, and for high suitability, 3 visits are required, at least 2 of which are during May-Aug. Site visits should be scheduled at least two weeks apart. Activity Surveys are carried out from April to October. Generally 3-7+ site visits are required, ideally a month apart. Winter Hibernation Surveys can be carried out Dec-Feb, sometimes later depending on the weather.

For more info, download a copy of our Survey Season Calendar.

What happens if you have bats?

If roosting bats are found on your site, you will need to obtain a licence prior to carrying out any otherwise unlawful activities which may affect the bats or their roosts. In many cases potential issues can be resolved through minor amendments to development plans – habitat retention or replacement, exclusion, timing of works to when bats are not present and Ecological Clerk of Works (supervision). The appropriate mitigation strategy will depend on the species of bat, abundance and their roosting behaviours. For larger sites, mitigation may include the preservation of foraging corridors with low levels of artificial light.

If you need a bat survey or even if you’re not quite sure what you need, please get in touch and we’d be happy to help.