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When determining a planning application, the Local Planning Authorities have a legal duty to consider the potentially adverse impacts of a development on roosting bats. For this reason, an initial bat survey is usually required prior to submission of a planning application. 


A Preliminary Roost Appraisal (PRA), or Phase 1 Bat survey, is an initial inspection of any building, tree or other suitable feature for roosting bats that could be affected by a proposed development. This survey may be conducted at any time of the year. A thorough search is made for evidence of roosting bats, such as the presence of live bats, bat droppings or feeding remains. Should evidence of roosting bats be recorded during the survey, the building, structure or tree would then be identified as a 'confirmed bat roost'.


Many of our native bats are crevice-dwelling species, and therefore potential evidence of these bats can be concealed due to the nature of their roosting habits. Should no evidence be recorded, the building / structure or tree's potential to support bats will then be assessed on a sliding scale of negligible to high:











If any of the affected buildings on site have evidence of bats or hold potential to support roosting bats, then further bat surveys may be required (see below) in accordance with the Bat Conservation Trust (BCT) guidelines (Colins, 2016). These surveys will determine the numbers of bats, species and type of roost(s) as well as locations of access points, which will be crucial in the design of a bat mitigation strategy. Where a ‘confirmed bat roost’ is identified, a bat licence may be required dependent upon the impact of the proposed works (see below).


Emergence / re-entry, activity surveys or phase 2 bat surveys, are follow-up surveys which are conducted after dark, either at dusk or dawn, and aim to identify the number of bats, species and roosting locations within the building, structure or tree. The surveys also aim to identify general bat activity, including commuting and foraging bats on site. The surveys typically involve a number of experienced bat surveyors using specialized bat detecting equipment to record the bat activity on site, as well as aiming to establish the type of bat roost(s).


Emergence / re-entry surveys are undertaken in accordance with 'The Bat Conservation Trust (BCT) Good Practice Guidelines' (Collins, 2016). The surveys are conducted in accordance with the following: 

  • The building / structure / tree has evidence of roosting bats or holds high potential to support roosting bats; three surveys will be required; moderate potential will require two surveys and low potential will require at least one survey. Negligible potential structures will not require further surveys.

  • Surveys must be undertaken between May-September, with at least two of the three surveys conducted between May-August during the optimal survey season.

  • The emergence / re-entry surveys must be conducted at least two weeks apart, to ensure the survey results are representative. 

  • The surveys must be conducted in suitable weather conditions for bats (i.e. low wind speed and no rain).

​Once the surveys have been completed, it is possible for planning permission to be obtained. A bat licence may then be required depending upon the proposed impacts of the works on the bat roost(s) on site (see below).


A bat licence must be obtained from Natural England prior to any works commencing if the proposed works have been identified to impact upon the bat roost(s) on site. The licence is a set of documents including a method statement, work schedule, bat mitigation strategy and survey results. The licence allows works that would otherwise be unlawful to proceed, and the licence holder, usually the client, has a legal responsibility to ensure all conditions of the licence are fulfilled. 

We are one of the few consultancies in the UK that offer the Bat Low-Impact Class Licence (BLICL). This licence is generally lower cost and the application process is quicker than the standard European Protected Species (EPS) bat licence. A BLICL can be obtained for lower numbers of certain common bat species.

Our experienced ecologists can prepare and submit the bat licence on your behalf. The following points should be noted in relation to licence applications:

  • Full planning permission must be granted prior to the bat licence application.

  • Depending on the time of year, licence applications can take up to 6 weeks to be processed and granted from Natural England for standard EPS licences (and up to 2 weeks for BLICL licence applications). This is an important point to consider when planning your works schedule, especially when appointing contractors and builders.

  • For a licence application to be granted, three "derogation tests' must be satisfied; the activity to be licensed must be for imperative reasons of 'overriding public interest' or for public health and safety; there must be no satisfactory alternative; and the favourable conservation status (FCS) of the bat species on the site must be maintained.    

Once the licence application is granted, a licensed bat ecologist will be required on site to supervise any activities that are anticipated to affect roosting bats, otherwise known as an ecological Clerk of Works (ECoW). The bat ecologist will provide a 'tool box' talk to contractors and give guidance for safely working around the bats on site in compliance with the bat licence. 


Bat activity transects are generally required where development proposals are likely to impact upon habitats that may be used by commuting, foraging or socialising bats. This type of survey involves ecologists walking a set route at a steady, constant speed around the site used hand-held bat detecting equipment. Additionally, static or automated bat detectors are set out in set locations to record bat activity throughout the night (see table below). In combination, these surveys provide an overall picture of the bat activity on site that will help inform a bat mitigation strategy.


You may require harp trapping if your site features suitable habitat for rarer bat species, and in particular bats listed under Annex II of the EC Habitats Directive; greater horseshoe (Rhinolophus ferrumequinum), lesser horseshoe (Rhinolophus hipposideros), barbastelle (Barbastella barbastellus) and Bechstein's bat (Myotis bechsteinii). This survey type involves a licensed bat ecologist humanely capturing bats using a trap and a sonic lure. This survey is useful in determining the presence / absence of breeding bats on site and can also be used to gain further information on rare or under-recorded bats on site. 

The bat data search that is undertaken as part of the bat report is often used to inform whether or not harp trapping is required. Should there be records of rare Annex II species within a 2 km radius of your site and your site features suitable habitats for this species, harp trapping is likely to be required following current national guidance.

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