The species receiving the strictest legal protection are generally referred to as ‘European Protected Species’ since they are protected under European Directives. Bats are a European Protected Species and are a material consideration within the planning process. The presence of bats on a site needs to be considered carefully and investigated thoroughly where considered appropriate.

Sonar Ecology are experienced bat specialists undertaking bat surveys, providing advice and designing mitigation for our clients. Dr Liat Wicks MCIEEM, director of Sonar Ecology has studied this group of animals  for over 16 years and has an in depth knowledge of their behaviour, ecology  and habitat requirements. Bats utilise linear features within the landscape to navigate and commute, flying along hedgerows, woodland edges and tree lines for example to get from their roost sites to favoured foraging grounds. Even if bats are not found to be roosting on a site, any severance of these habitat features on a site is likely to cause negative impacts to local colonies. Understanding how bats use a site is therefore important in order to conserve this species locally.

Experts in acoustic survey techniques and data analysis, we are able to assist with even the most demanding projects, and have the necessary bat detecting equipment, digital recording devices and sound analysis software to be able to determine presence or absence, estimate numbers, identify species and assess how bats are using a site.


Surveying for bats need not be a headache for clients – the key is gathering sufficient information on bats, and in the timing of surveys. If you know your site has either built structures, mature trees and good habitat features such as water bodies, tree lines, woodland and hedgerows then it is likely that bats could be using the site in some way, and it is best to seek the advice of an experienced bat ecologist early on in the project, as to the recommended approach.

Bat surveys generally follow a phased approach with an initial assessment of features informing the subsequent level of survey effort and type of survey. Initial surveys include the following and are informed by a detailed desk study:

  1. Initial Habitat Assessment – usually via a Phase 1 Habitat Survey which will reveal if suitable habitat features exist for bats
  2. Initial Building Assessment – daytime external and internal inspection (looking for evidence of bats or bats themselves)
  3. Initial Tree Roost Assessment – daytime external assessment and internal where possible resulting in a grading of bat roost potential for each tree/group of trees

If no bats are found and the structure(s) are considered unsuitable for roosting bats then a technical report will be drafted to state the results and satisfy the local authorities that this species has been considered within the planning process.

If there is good potential for bats to be roosting within structures, or evidence of bats are found, the following steps are likely to be required:

  1. Night time surveys; a combination of dusk emergence and dawn re entry surveys to confidently determine presence/ absence, species and estimated numbers.
  2. Activity surveys to determine how bats are using the site and the habitat features within the site.

The results of these surveys will generally be sufficient along with outline mitigation to support a planning application and demonstrate that sufficient data has been collected in order for any impacts of the proposed development on bats to be determined. This is crucial to the success of planning applications, as local authorities will not condition bat surveys or consider applications that do not have sufficient supporting information on a protected species.

If roosts are identified, additional surveys and detailed mitigation will be required to support a European Protected Species licence (also known as a mitigation licence) application once planning permission has been granted.

For further information click on our Bat Surveys link to see how we could help you.