Bat Surveys2019-05-26T11:46:23+01:00

Bat Surveys

Bat surveys are required for a number of reasons. You may have been asked by a local planning authority, architect or county ecologist. The most common being to support a planning permission application.

Although the term ‘bat survey’ is commonly used, there are actually 3 processes involved when it comes to bats. A preliminary roost assessment, Bat Activity Survey and Mitigation. Although, in most cases and unless bats are identified as using any buildings, trees or structures effected by developments, you may not require all steps be taken.

All 18 UK bat species are protected by law, under the the Habitats Regulations 2010. The regulation means that it is an offence to intentionally or recklessly kill or injure a bat and damage, destroy or obstruct a bat roost. Handling or capturing a bat without an ecology licence is also an offence.

With a team of fully licensed ecologists, we offer a proven bat survey strategy with a 100% success in obtaining protected species licences for our clients.

Bat Surveys

The Definitive Guide to Bats: Surveys & Mitigation

So, you have put in you planning application. The local planning authority has stated an ecological bat survey is required. You probably have a few questions.

Below is probably the most comprehensive guide to bat ecology available online. We hope this guide answers everything there is to know about bat surveys.


  1. Why do I need a bat survey?
  2. Will I need to carry out a survey?
  3. Deciding if you need ecological surveys
  4. I think we need a survey
  5. What happens on an ecology survey?
  6. What do ecologists look for during dusk and dawn bat surveys?
  7. Mitigation and compensation for bat species
  8. What happens after a protect species licence is granted?
  9. What happens if we discover bats after development has started?
  10. How much does a bat survey cost?

Why do I need a bat survey?

Well, it’s not uncommon especially if you are demolishing a building, breaking into a loft void or live in a bat friendly area.

Bat survey reports are required for development projects that may affect protected species. Bats along with Newts, nesting birds and many other species are all protected under the The Wildlife and Countryside Act (as amended) 1981.

At this point, we’d like to give you some good news. Bats almost never stop your development.

But what is the bat survey and mitigation process? Firstly, a preliminary roost assessment (also known as a phase 1 survey) will take place. This process will highlight any potential for bats to live within your structure.

If potential is shown dusk and dawn surveys need to be completed. These surveys need to show whether protected species are present in the area, and how they use the site.

If species are detected, then a mitigation plan is designed to show how you’ll avoid, reduce or manage any negative effects to protected species. Working with your ecologist you need to decide which methods are right for the project you’re working on. A mitigation licence from Natural England is required. Once received the moving of bats to a new home can then take place.

Will I need to carry out a bat survey?

The simple answer is probably. Yes! you will need a survey.

If you plan to carry out development that could disrupt or harm bats or their roosts and your local planning authority has asked for a survey then you will need to carry out a bat survey.

Typically barn conversions, demolition, extensions and tree removal require ecological surveys and potentially mitigation.

However, there are a few areas to consider whether your work will be affected.

Deciding if you need ecological surveys

Bats and other protected species can be affected by lots construction work including:

  • demolition of buildings
  • extensions that effect or alter roof voids
  • wind turbines
  • barn conversions
  • removal of trees or hedgerows
  • building or maintenance of roads

You’re more likely to find bats using a building if the property has favourable features such as:

  • cracks or crevices in brick work or fascias
  • has a roof with loose or slipped tiles
  • has hanging tiles or wood cladding
  • is close to woodland or water
  • has an uneven roof covering with gaps
  • has entrances bats can fly into
  • has a large roof area with clear flying spaces
  • has large roof timbers with cracks, joints and holes

Some Bat species may hibernate underground in winter. Especially if it:

  • is large enough to have a stable temperature
  • is close to woodland or water
  • is holds humidity

You’re likely to need a bat survey for tree removal if it:

  • is in ancient woodland
  • is large with a good growth
  • has natural cavities or split branches
  • has damage caused by wind, woodpeckers, rot or lightning
  • has loose bark

I think we need a survey

If your planning or development has any of the above bullet points ticked then, YES! you need a bat survey.

So what actually happens on the ecological survey process?

Well it’s fairly simple. Bats will almost never stop your development.

What happens on an ecology survey?

So, now you’ve established why you need a survey, you maybe be wondering what happens during the survey process.

The bat survey process is straight forward. It involves 3 main processes. Preliminary roost assessments, activity surveys and mitigation.

If your local planning authority has asked for a survey then you will need to contact a licensed ecologist.

Typically, after a phone consultation the ecologist will then require a visit to your site. This is called a Phase 1 or preliminary roost assessment.

Preliminary roost assessments

For most planning permission applications or development projects involving bats it is appropriate to start with a Phase 1 also known as a Preliminary Roost Assessment or Scoping Survey.

Preliminary Roost Assessments involve an initial internal and external inspection of a building or habitat to identify the potential for bats roosting.

As well as an assessment of the building and surrounding habitat to support bats, a phase 1 survey may require a data records search. Meaning, records such as known bat roosts, previous mitigations and the location of SSI’s and LNR are obtained.

The desk based assessments are a requirement and are usually purchased from third party biological records centres. If the building itself does not show evidence or potential of bat roosts then this information can sometimes be enough to provide an assessment of whether bats are likely to be present on site and whether they are likely to be impacted upon by the development.

After the data is collected your ecologist will compile a detailed report outlining any further steps which maybe required.

Bat activity surveys

Should evidence or potential for bats be identified via phase 1, further survey effort is required. This next stage is activity surveys also known as emergence and re-entry or dusk and dawn.

Preliminary roost assessments can be carried out year round. However, activity surveys will need to be undertaken between May and September. The weather conditions must be dry and ideally above 7 degrees celsius.

The surveys will be carried out at dusk and/or dawn to establish the species, how many and over what time period bats maybe using the structure or habitat.

The team will consist of at least two ecologists, depending on the size and layout of the building or habitat. All elevations need to be covered. They will survey Dusk or Dawn to see if any bats emerge or enter the building. A return visit will be planned for at least 15 days after. It is important to note that 2 surveys carried out within the same 24 hour period counts only as one survey.

Up to three emergence/re-entry surveys are required to assist in determining the type of roost which is present and the species using them.

What do ecologists look for during dusk and dawn bat surveys?

The activity surveys allows ecologists to identify the usage of the habitat such as;

  1. Day roosts – individual bats, or small groups of males, are using the area for shelter during daylight hours
  2. Feeding roost – where bats, particularly BLE and Horseshoe species feed during the night
  3. Night roost – where bats rest or shelter between feeding sessions
  4. Hibernation roost – where bats hibernate over the winter periods
  5. Transitional or occasional roost – where bats gather at a temporary site before and after hibernation
  6. Mating site – Males and females gather together in late summer to early winter
  7. Maternity roost – where babies are born and raised until they’re independent
  8. Satellite roost – where breeding females roost close to the main nursery colony in the breeding season
  9. Swarming site – where bats gather in large numbers from late summer to autumn

Mitigation and compensation for bat species 

Should evidence show that bats are identified via activity surveys, the final step will be bat mitigation and compensation.

Working with your ecology consultant you will design a mitigation plan. This involves applying to Natural England for a protected species licence. However, you will need planning permission to have been granted prior to applying for this licence.

For the licence to be granted, a mitigation strategy will be required that could involve timings of works, installation of bat boxes (both external and internal) and/or creation of a bat loft for void-dwelling species (such as brown long-eared).

In some instances the best solution can be a stand-alone ‘bat house’. Bat access roof tiles may also provide a good solution to a development.

Lower impact measures may require just the installation of a bat box or two. This method is sufficient in the instance of a single crevice dwelling bat, such as a common pipistrelle.

The mitigation plan will address the potential impacts on bats and must avoid negative effects on bat roosts, such as a small alternations to project designs.

If this is not possible, the use of alternative mitigation measures to reduce the impacts must be implemented.

Mitigation and compensation methods can include:

  1. Changing work methods or timing to avoid roosting periods. For example, work to be complete during winter on summer roosts.
  2. Creating new roosts within the same building or on neighbouring structure
  3. Improving or creating habitats. Such as, new foraging areas
  4. Long term management of habitats
  5. Roost monitoring after the development

What happens after a protect species licence is granted?

So all the correct paperwork is in place and Natural England have granted your protect species licence. But what happens next?

The ecologist, architect, construction company and yourself will decide on a date whereby work will be started. The ecology consultant will take one or both of two main steps:

  1. Implement any compensation measures for void-dwelling bats before works are undertaken.
  2. And/or – Be on site to undertake ecological clerk of works measures during a soft break of any areas where crevice-dwelling species are identified.

Once any bats are ‘mitigated’ in to the new roost works can continue as normal.

What happens if we discover bats after development has started?

Stop all work immediately. Continuing work is likely to be breaking the law if bats are found during building works. Get in touch with your ecologist who will come and mitigate your bat.

How much does a bat survey cost?

Well, it’s hard to accurately say as it varies greatly. There are many factors to take in to account.

Phase 1 ecological surveys range from between £300 – £1000 depending on the ecologists fees, location and size of the site. And as of 2019, despite strong opposition from ecology consultancies, Natural England now charge for the mitigation licence.

Bat Survey Calendar

Preliminary Roost Assessment

bat survey times

Activity Bat Surveys

bat surveys

Survey Key

ecology survey times