Bat Surveys
There are 18 species of bat in the UK, all of which are protected under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017, which make it an offense to:
- Intentionally or recklessly kill, injure, or capture a bat.
- Disturb a bat in a place of shelter or rest.
- Damage, destroy, or block access to a bat roost (whether bats are present or not).
Where a development may affect bats or their habitat, bat surveys are required to assess their presence, activity, and potential roosts.
Bats can be affected by works including:
- Demolition/maintenance of structures
- Renovations to structures, bridges or tunnels
- Conversion of churches, buildings or derelict properties
- Tree/Hedgerow removal
- Developments causing noise and light pollution
- Developments removing green space, trees, hedgerows or ponds.
If your Preliminary Ecological Appraisal or Preliminary Roost Assessment has highlighted concerns about bats within your site - you may need one or more of the bats surveys listed down below:
Adonis Blue will work with you to carry out the necessary surveys to determine the presence of bats and attain a bat survey license on your site if necessary.
The best time of year to conduct a bat survey can be found within our ecology calendar.
Call Adonis Blue on 01622 357 821 or email hello@adonisblue.org.uk to arrange a quote
Bat Surveys
Here are the main types of bat surveys used in development contexts:
Preliminary Roost Assessment (PRA)
- Purpose: Identify buildings or structures with potential to support roosting bats,
- Method: Visual external and internal inspection of features like cracks, holes, roof voids, or droppings
- Timing: Year-round, ideally during daylight
- Number of surveys: One (may require more on complicated or large sites)
Ground level tree assessments (GLTA)
- Purpose: Inspect potential roost features in trees, used when trees are due to be affected and have roost potential
- Method: Each tree is thoroughly examined from the ground for any roosting features.
- Timing: Year-round, ideally during daylight
- Number of surveys: One (may require more on complicated or large sites)
Tree-climbing or Aerial assessment surveys
- Purpose: Inspect potential roost features in trees, used when trees are due to be affected and have roost potential
- Method: Licensed arborists or ecologists climb trees to inspect cavities, cracks, or loose bark
- Timing: Late Spring to Early Autumn (May to September) is optimal
- Number of surveys: One (may require more on complicated or large sites)
Emergence (Roost) Surveys
- Purpose: Confirm presence of bats emerging from a roost, after a PRA / PEA identifies potential roost features
- Method: Observers watch structures at dusk using bat detectors
- Timing: May to September (peak activity season), with June–August preferred
- Number of surveys: Can range from 1 to 3 surveys, depending on the roosting suitability identified from the PRA / PEA.
Activity (Transect) Surveys
- Purpose: Record bat activity levels across a site to assess commuting routes and foraging areas, especially where habitat changes are planned
- Method: Surveyors walk a fixed route (transect) with bat detectors to detect flying bats
- Timing: Dusk to a two hours after dark, May to September
- Number of surveys: Can range from monthly to seasonal surveys, depending on the commuting and foraging suitability identified from the PRA / PEA.
- Automatic static detector surveys are often used in conjunction with these surveys.
Automated Static Detector Surveys
- Purpose: Record bat activity continuously over several nights, to detect less common species, understand daily patterns, or survey large/remote areas.
- Method: Static bat detectors are left in place to log bat calls (for often 5 nights)
- Timing: Put out for 5 consecutive nights, monthly from April-October
- Number of surveys: Monthly (7 deployment in total)
Hibernation Surveys
- Purpose: Identify and assess hibernation roosts (e.g., caves, basements)
- Method: Careful internal inspections, sometimes using endoscopes, thermal imaging or statics
- Timing: Winter months (typically December to February)
- Number of surveys: at least 2 visits, with a third visit recommended for high-risk sites
- Automatic static detector surveys are often used in conjunction with these surveys.
DNA and Environmental Sampling
- Purpose: Detect bat presence from droppings, swabs, or environmental DNA (eDNA)
- Use case: Support traditional methods or confirm species from droppings
- Limitation: Not a stand-alone method for legal purposes (yet)
Obtain a protected species license
To obtain a bat licence for development, you need to apply for a bat mitigation licence from the relevant statutory nature conservation body.
This licence is legally required if your development will disturb bats or damage/destroy a known or suspected roost, even if bats are not currently present at the time of the works.
Our team can help you secure a bat licence and ensure all necessary data is gathered, so it can be submitted as part of your planning application.