What we offer

Greenlight Environmental Consultancy offers a wide range of services with respect to bat surveys, including:

  • Preliminary Ecological Appraisal (“PEA”) – An initial site assessment to identify habitats present on site that may support protected species. This includes a site visit and a desktop assessment. A PEA is typically required as a first step to address the ecological aspects of a planning application. The PEA would recommend if further bat surveys are necessary, and appropriate mitigation and enhancements for the proposed development.
  • Preliminary Roost Assessment (“PRA”) – An assessment of buildings, trees and surrounding habitats to determine their suitability for roosting bats. A PRA is often required for barn conversions to residential use. The PRA would recommend if further surveys are deemed necessary to support a planning application.
  • Emergence and re-entry surveys – Night-time surveys using bat recording and night vision equipment to confirm the
    absence/presence of bats at a building or tree. These bat surveys would help to determine which species of bat are present, how many, and the type of roost (e.g. maternity, non-breeding, hibernation etc.)
  • Activity surveys – Walked transect or static detector surveys to determine the absence/presence of bats commuting and/or foraging on a site.
  • European Protected Species (“EPS”) Mitigation Licences – A licence issued by Natural England under the Conservation of Species and Habitats Regulations 2010 (as amended) to capture or disturb individual bats and to obstruct, modify, or destroy their breeding/resting places.
  • Overseeing construction works (including toolbox talks) – A watching brief during construction works, often undertaken under an EPS mitigation licence, to avoid killing or injuring individual bats.


Bats are the only true flying mammal and there are currently 18 species of bat in the UK, 17 of which are known to be breeding in the UK. They make up almost one quarter of UK mammal species and are suffering population declines due to a variety of factors. Although these factors differ between species, they include the loss and degradation of habitats and roosts (destruction of ancient woodland, building renovations, agricultural intensification, etc.), poisoning via chemicals found in treated timbers, and poor water quality affecting aquatic invertebrate abundance on which some species rely (BCT, 2013).

Bats are nocturnal insectivores, that feed on a variety of species such as gnats, midges, mosquitoes, spiders, beetles and moths. They find their prey by echolocation – producing a stream of high pitched calls and listening for echoes reflected by objects. This allows bats to create a sound picture of their environment. Most of these echolocation calls are too high pitched for humans to hear, but electronic bat detectors allow us to listen and identify species by these calls.


All bat species are protected under UK and European Union (“EU”) laws, including:

Under these legislations all bats are protected from:

  • Capturing, killing, injuring and disturbing;
  • Damaging or destroying breeding/resting places;
  • Obstructing access to resting places; and
  • Possessing, advertising for sale, selling or transporting for sale, live or dead (part or derivative).

In simple terms: all development proposals which have the potential to impact on local biodiversity, and Local Planning Authorities (“LPA”) require sufficient information to make informed decisions that wildlife can be protected from injury or disturbance during the development. They often require a Preliminary Ecological Appraisal (“PEA”) or Preliminary Roost Assessment (“PRA”), and further bat surveys if bats, or signs of bats, are found to be present.

If bats are roosting on a site for development, it is likely that a European protected species (“EPS”) license and an appropriate mitigation strategy will be required in order to proceed with the works.


Each species prefers to roost in certain locations as described in the table below (Mitchell-Jones, 2004).

Bat habitats

Bats occupy a variety of different habitats, but the highest densities occur where insects are most plentiful, such as areas of wetland and woodland edges. Research has shown that many bat species are reluctant to cross wide open spaces, instead following linear features such as hedgerows, treelines and waterways.

The most frequently encountered species are the common pipistrelle Pipistrellus pipistrellus, soprano pipistrelle Pipistrellus pygmaeus and brown long-eared bat Plecotus auritus.



Bat surveys are highly seasonal and are split into three main groupings:

  1. PRA and tree inspections
  2. Summer activity
  3. Hibernation

If the PRA or tree inspection find bats occupying a site, further bat surveys may be required in the form of summer activity and/or hibernation surveys.

Bat surveys (timing)

Mitigation and enhancements

There are numerous forms of mitigation and enhancements, with each design being tailored specifically to address issues raised at the site in question. Previous mitigation designs have included the construction of bat lofts, saddle roosts for derelict barns, roosts under roof tiles and behind weatherboarding, the installation of integrated and standalone bat boxes, and low lighting schemes. Enhancements may include roost creation, planting of hedgerows and creation of ponds.



BCT (2013), Competencies for species survey: Bats, Charted Institute of Ecology and Environmental Management, Hampshire.

Collins, J. (Ed.) (2016), Bat Surveys for Professional Ecologists: Good Practice Guidelines (3rd edn.), The Bat Conservation Trust, London.

Mitchell-Jones (2004), Bat mitigation guidelines, English Nature: Peterborough.