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BAT SURVEYS
A bat survey is commonly requested when the conversion, modification or removal of a building or other structure is proposed, and at sites with mature trees. 

There are 18 species of bat in Britain. These nocturnal mammals take shelter during the day in roosts which, depending on the species, can be attic spaces, small crevices, cracks, and holes in buildings, trees or other man-made structures like bridges. Roosts can be used by single bats (sometimes for very short periods of time each year) or by hundreds during the breeding and hibernation seasons.

Bats feed on insects which they hunt in a variety of habitats, notably broadleaf woodland, tree-lined water features and grazed parkland but are also commonly seen feeding in mature residential gardens. The distance between a roost and a bat's favoured feeding area may be considerable and they rely on strong landscape features such as hedgerows to navigate or ‘commute’ between the two.

Each species of British bat is a European Protected Species. Legislation dictates that any structures or place which a bat use for shelter or protection are protected from damage or destruction whether occupied or not. Planning authorities are legally obliged to refuse planning permission until the presence or otherwise (likely absence) of bats, and the extent that they may be affected by the proposed development, is established by survey.

A bat survey is commonly requested when the conversion, modification or removal of a building or other structure is proposed or on sites with mature trees. There are a number of methods to survey for bats and, depending on the information required, one or all of the techniques outlined below may be used. There are seasonal constraints to some bat surveys. For more information please see our Survey Calendar >>>

We can advise on the most appropriate survey method for your project. Our bat surveys come at competitive prices and follow the most current survey guidelines set out by the Bat Conservation Trust. 
Preliminary Roost Assessment

Preliminary Roost Assessment (PRA) can be undertaken all year. Any site buildings (or other man-made structures) and/or trees are inspected for evidence of bats and to identify any features, e.g. holes, cracks, lifted roof tiles, etc., that could potentially be used by them as a roost. ​

The suitability for bat roosting of each of the structures or trees surveyed is classified as negligible, low, moderate or high, according to current best practice guidance, to indicate the likelihood of roosting bats being present. The result of the assessment is used to inform the scale of any further survey effort that may be required to confirm the presence or likely absence of roosting bats or, if suitability is poor, rule out that need.
Roosting Presence or Likely Absence Survey

Also known as "emergence and re-entry survey", these surveys are undertaken May-August (-September) at dusk or dawn respectively, to see if bats emerge from or return to a roost site. Depending on the results of the PRA, between one and three surveys visits to the structures or trees that were classified as suitable by the Preliminary Roost Assessment will usually be required.

The surveys usually involve two or more surveyors with bat detectors positioned around the building or tree to look for any bats leaving or returning to a roost, making note of the species and number of any roosting bats recorded and the entry/exit point of the roost.
Activity Transect Survey

This survey is used to identify habitat features within a site that are important to hunting (foraging) and commuting bats and which species are using them. The suitability of the site habitats for these activities will have been assessed during the site's Preliminary Ecological Appraisal and any activity survey effort required will be determined by that assessment.

The survey involves surveyors walking a predetermined route or "transect" on several nights in the season using bat detectors to record the species and location of any bats detected or seen and a note of the bat's behaviour (foraging, commuting, etc.)

If bats are found and the proposed works are likely to result in an unlawful act, e.g. damaging a roost or disturbing bats, a licence must be sought from the relevant statutory body, e.g. Natural England. The license ensures that works are undertaken in a controlled and legal manner. The licence application should be completed by an experienced ecologist on behalf of the licensee (the developer).
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