Bat Surveys and their Impact on Planning


REC Ecologist Katie Bird heads out on site with environmental scientist colleagues, Marc Roberts and Alasdair Brooker, to explore the potential impact of Bat Surveys on planning if not completed in season.

Bat Roost Survey

Derelict and abandoned sites often present habitat opportunities for wildlife. This former car garage was no exception. Due to various nooks, crevices and uneven roofs, the site had a high potential for bat roosts. With it being peak bat survey season, the REC team headed out on site to establish any evidence for such bat activity.

All bats and their breeding sites are protected by law in the UK. Natural England requires that any development that could affect protected species,  needs surveying and mitigation plans completed prior to planning permission being approved. Sometimes bat surveys are not requested by the council until planning permission has been submitted, and sometimes surveys are requested once the designated survey season has passed. It is illegal for development to continue if evidence of bat activity has been discovered during works, and a survey within season will be required before being resumed.

Whilst Daytime Bat Scoping Surveys (sometimes known as preliminary roost assessments) can be carried out at any time of the year, bat surveys (often called bat emergence/ re-entry surveys or dusk/dawn surveys) are seasonally restricted between the months of May and September and are generally required where evidence of bat activity or habitat value is present on a site.


Bat hibernation in the winter months means that bat surveys can only be done during the summer (May to September) when the species are active. If missed, then this can result in significant delays to development. The same can occur if a survey is requested after the bat roost season has finished; for example, if an application is submitted and considered later on during the year. It is crucial, therefore, that any planning applications for developments that have the potential to impact protected species, allocate time for  bat surveys to be conducted as soon as possible.

Generally, the larger the site, the more vantage points there are to cover – so a team of three was essential for a site of this size. Best Practice Guidelines state that bat emergence surveys have to  start at least 15 minutes before dusk and last for up to 2 hours afterwards, meaning that the team were on site for a good while after sunset. For a dawn re-entry survey, surveyors begin approximately 1.5 hours before dawn and continue at least 15 minutes after. Being on site early in the morning and late at night means that a flask of tea and a warm blanket, as well as bat detection equipment (measuring sound frequency and echolocation) are essential items of kit for any bat survey.

Bat Roost Season

A bat emergence survey is used to confirm or discount the presence of roosting bats within a building that has been assessed as having the potential to support the species during the daytime bat scoping survey.  Our team, therefore, were looking for potential roost features, which can include the inside of crevices, south facing aspects (due to the warmer climate), dense ivy and hanging tiles, and watched these features throughout the survey for any bats leaving. Some bats such as the Common Pipistrelle, can fit into holes as small as a 20 pence piece, so it is essential that every corner is covered.

On this occasion, no signs of bat roosting activity were found at the site and therefore mitigation measures will not be required – allowing development to go ahead. However, if evidence had been found, then depending on the quantity of bats, a Natural England Bat Mitigation License would have been required as well as mitigation measures such as bat boxes for roosting and additional shrubbery (to provide insects to feed on) would have been required.  Irrespective, it is essential to consider potential for such protected species early on in the development process so that any required surveys (if any) do not interrupt or delay planning and development later on.

Bat Survey Advice

If you need advice or have any questions about Ecological Surveys, please don’t hesitate to get in touch with Senior Ecologist, Olivia Winter at:, or 0161 868 1300.