Need a Bat Emergence Survey?

What You Need to Know About Bat Emergence and Re-Entry Surveys (BERS)

If you’re planning a development and there’s a chance of bat activity on your site, a Bat Emergence Survey could be a crucial part of your planning application. These bat surveys are a legal requirement in many cases; understanding how they work and why they matter will help you move forward with your scheme confidently and help you to achieve planning permission.

What is a Bat Emergence Survey?

A Bat Emergence Survey, also known as a Bat Emergence and Re-entry Survey (BERS), is a detailed ecological assessment carried out at dusk and dawn to monitor bat activity and find out if there are roosts present. It helps determine whether bats are using a building, tree, or other structure with high suitability for roosting, and if so, how they use the site.

These surveys are typically required when a Preliminary Roost Assessment, an initial assessment, identifies signs of bats or potential roosting features that could support bats, such as access points under roof tiles or hanging tiles, ridge tiles, weather boarding, spaces in brickwork which could be used by crevice dwelling bats, or signs like droppings or feeding remains.

If there is evidence of bats, or there is a reasonable likelihood of bats being present, a more detailed assessment is required: BERS then becomes the next step in understanding how development might affect them and the further action to take.

When Are Bat Surveys Carried Out?

BERS are seasonally restricted and must be carried out during the active bat season – they are typically undertaken between May and September, when bats are neither hibernating nor rearing young. While bat surveys can sometimes start in April or continue into early October, the optimal time is from May to September, in line with good practice guidelines set by the Bat Conservation Trust (BCT).

Emergence and re-entry observations are conducted around sunset and sunrise, when bats are most active. Dusk emergence surveys usually begin 15 minutes before sunset and continue for up to two hours after, while dawn re entry surveys commence two hours before sunrise and conclude 15 minutes after. Access points for bats will be closely monitored using specialist equipment.

These bat activity surveys will need to take place over several visits during the bat survey season to fully assess a proposed development site and determine the presence of bats, or absence of bats.

Why Are Bat Surveys Important?

Bats are legally protected in the UK under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017. These laws make it an offence to disturb, harm or destroy bats or their roosts, whether or not bats are present at the time, or obstruct access for bats.

This legal protection exists because many of the UK’s 18 native bat species have seen significant population declines over recent decades. Habitat loss, development, and environmental changes have all played a role in their decreasing numbers, resulting in their status as a fully protected priority species.

Therefore, if bats are present on your site, the local planning authority will need evidence that your proposed development works will avoid disturbing bats. A BERS provides the necessary data to develop a mitigation strategy and demonstrate your legal compliance with bat survey guidelines, habitats regulations, Natural England and Natural Resources Wales requirements.

What Happens During a Bat Emergence Survey?

Carried out by qualified and licensed ecologists, these surveys involve multiple visits – typically three surveys – to a proposed development site to observe and record bat activity. Professional ecologists holding a European protected species licence will make an internal and external inspection of buildings with the potential to support roosting bats.

A physical inspection will also be made of any natural habitats and trees which could provide shelter or roosting sites for bats.

Using a combination of infrared cameras, bat detectors, night vision aids, and sometimes thermal imaging or audio recording devices, experienced ecologists monitor entry and exit points to and from potential roosts.

These bat surveys aim to identify:

• The species of bats present
• The number of bats
• The type of bat roost (e.g. day roost, maternity roost, hibernation roost)
• The function of the site: it may be used for breeding, resting or feeding

In some cases, additional techniques such as radio tagging or bat DNA analysis may be employed for more in-depth monitoring.

What Happens After the Survey?

All findings from the bat activity surveys are compiled into a comprehensive Bat Emergence Survey report, which can be submitted as part of a planning application made to a local planning authority. The report includes the survey methodology and:

• Details of species observed
• Activity patterns and bat roost characteristics
• Assessment of potential impacts of your development
• Recommendations for mitigation work or compensation measures
• Details of any further surveys required

Mitigation and Licensing

If bats are found on your site, it doesn’t automatically mean your development plans are halted. What it does mean is that mitigation may be needed. Mitigation strategies are designed to reduce harm to bats and may involve:

• Installing boxes for bats or bat access tiles
• Retaining and protecting existing roosts
• Creating new roosting spaces in nearby structures or trees
• Altering the timing or methods of your construction work

The complexity of mitigation will depend on the species present. For example, a solitary common pipistrelle may require minimal mitigation, while a maternity colony of rare barbastelle bats will need a much more detailed plan.

If significant impacts are likely, ecologists can assist with applying for a bat mitigation class licence, which gives legal permission to proceed with the works under strict conditions.

Who Requires a BERS?

These bat surveys are often required when:

• Alterations are planned for buildings, particularly older or derelict ones
• Trees with potential bat roost features are to be felled or trimmed
• Proposals include demolition, barn conversions or roof works
• There’s a likelihood of impacting nearby roosting, foraging or commuting routes

Whether your project is a domestic extension or a large commercial development, a BERS can help ensure compliance with both UK and European legislation while keeping your timeline on track with local council requirements.

How Much Does a Bat Emergence Survey Cost?

Costs for a Bat Emergence Survey vary depending on the size and complexity of the site, the number of surveyors needed, and how many visits are required. On average, you can expect to pay from £789+VAT, though this figure may increase if multiple visits or a larger team is required.

While BERS are more expensive than the preliminary roost assessment pra, investing in one early can prevent costly delays later, especially if bat activity is discovered late in the planning process.

Need a Bat Survey? Plan Ahead

If your development proposals have high potential to affect bats or their habitats, arranging a BERS is not just a legal obligation, it’s one of the necessary steps to take before you can obtain planning permission from local authorities.

Early engagement with expert ecologists working for an experienced ecological consultancy can help you:

• Meet local planning authority planning requirements
• Comply with relevant legislation
• Minimise delays and additional costs by carrying out a survey at the best time (ideally surveys undertaken between May and September)
• Support local wildlife populations and the natural environment
• Create an environmental management plan if required

By working with licensed consultants and following good practice guidelines, you can ensure your new development is both legally compliant and environmentally responsible and that surveys are undertaken at the correct time of the year.

Following these steps will give you the best chance of achieving a successful full planning application, despite the presence of bats and their roosts.