Why do I need a bat survey?

The increasing amount of development in the UK has had a huge impact on bat populations. All 18 native species of bat have been affected – population numbers have dropped dramatically over the last century due to habitat loss impacting bat roosts and feeding habitat.

As a result, relevant legislation has developed so that bats are fully protected. Bats are legally protected (along with other European protected species) under the Wildlife and Countryside Act 1981 (as amended) and the Conservation of Habitats and Species Regulations (2017), which make it an offence to deliberately kill or disturb bats, deliberately capture bats, damage or destroy their habitat or obstruct access to their resting places.

A common pipistrelle in flight.

Anyone carrying out a building or development project which may affect bats must prove to the planning authority that all the required steps are being followed to avoid disturbing bats or a bats’ roost. If the presence of bats is identified on a development site, a local planning authority will require evidence of mitigation to allow for the bats.

However, if you do find bats it does not signal the end of your development proposals; you may be able to go ahead in certain circumstances providing that appropriate mitigation and compensation measures are put in place for the species of bat, population, and roost type. Often, a different approach may need to be taken to avoid disturbance to the bats. Local planning authorities differ in their requirements, so it’s advisable to find out what your specific planning department will ask for.

It’s important to get the required bat surveys completed before any work starts to put yourself in the best position with the information to hand. Discovering bats when work is underway could prove costly and time-consuming, and put you at risk of prosecution. Bear in mind that Natural England regards bat surveys as having a shelf life of under two seasons old.

Development that might impact bats

This includes small maintenance works such as repointing walls, rewiring, and repairing doors and windows, and more major works such as maintaining chimneys, roof repairs and tree removal. Ideal environments for bats include agricultural buildings, often in rural communities close to the natural environment where they can forage for food.

If your project needs a bat survey, the first step is to have a Preliminary Roost Survey (PRA), or scoping bat survey; this is an initial assessment carried out to find out if bats are present.

A Nathusius bat is one of many protected species of bat.

Bat surveys

Preliminary Roost Assessment (PRA)

This physical inspection survey can be carried out at any time of year. A licensed bat surveyor will examine your site and existing building for signs of bats, looking for bat droppings, urine stains, feeding remains such as live or dead bat carcasses, or potential roosting features for crevice dwelling bats such as slate roofs, a spacious roof area, weather boarding, roof voids, or hanging tiles.

Buildings with high potential for bat activity and roosting opportunities include barn conversions, livestock buildings, or buildings close to woodland, bats’ natural habitats, breeding sites and foraging areas. If preliminary roost assessments reveal evidence of bats, you will need further surveys as part of the planning process, usually a second-stage survey, known as a Bat Emergence Survey or BERS.

Bat Emergence Survey (BERS)

The important thing to think about with BERS is that they can only be carried out in the summer months between May and September; these are the key bat survey season months as they are outside the bat hibernation season. It’s worth noting that weather conditions such as heavy rain and high winds can cause bat activity surveys to be cancelled, so factor this in and book early.

BERS are often called dusk and dawn surveys as they must be undertaken 15 minutes before, or two hours after sunset, or two hours before or 15 minutes after sunrise. Several visits are required in daylight hours over the summer to collect sufficient information, according to bat survey guidelines, often involving two or three surveyors (licensed ecologists) to cover access points on all the angles of a building.

During the bat survey, the professional ecologist will carry out an internal and external inspection of the site, using technology to assess the number of bats, and voice recorders that convert their echolocation calls into a frequency readout which helps with species identification. They will look at flight paths, places that might support roosting bats, and conduct emergence and re entry surveys to detect the presence of bats. The bat activity surveyors must use equipment such as bat detectors, infrared, night vision, and thermal imaging cameras to assess bat activity and record bats along with other survey data.

An important part of the survey is identifying the type of bat roost – bats use a range of roosts for different reasons at different times of the year. These include day roosts, night roosts, hibernation roosts, maternity roosts, foraging roosts, and transitional roosts.

Once the bat species and type of roost are established, the licensed bat ecologist can suggest appropriate mitigation measures and possibly a habitat enhancement plan as part of the bat survey report which may allow your development proposal to proceed.

The report will contain other findings and bat mitigation recommendations which can be submitted to the local planning authority alongside an application for planning permission. If the council then grants a planning application, you can apply for the required bat mitigation class licence to enable you to make alterations to your scheme based on the mitigation proposals from the bat survey.

Bat boxes.

Mitigation if there are bats present on your development site

Depending on the bat species, acceptable mitigation work might include avoiding bat roost areas during the development scheme or safely relocating bats. Simpler steps could involve installing boxes as pictured above or fitting bat access tiles on buildings or weather boarding.

A bat survey will put you in the best position

As explained above, UK bat species and their habitat are highly protected by statutory nature conservation organisations and legislation: arming yourself with as much information as possible about your planning authority’s requirements in terms of bat surveys and mitigation is essential to the success of your development proposal.

If you think that bats may be present in your proposed development, professional ecologists with a bat licence will be able to offer further advice and a detailed assessment of your site, along with bat survey cost details. Obtaining this expert advice as early as possible will give your planning application the best chance of success.

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