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What is a Bat Survey?

Bat surveys are requested, usually by a planning authority, to determine the effects of a development on bat species and to identify the necessary mitigation to reduce or compensate when the development involves:

  • Demolition or renovation of buildings
  • Loss of hedgerows or large mature trees adjacent to known bat roosts
  • Road schemes
  • Wind farms

There are a number of different types of bat surveys: roost surveys (the resting place of a bat); commuting route surveys (travel paths to and from roosts and feeding areas) and feeding surveys (habitats where bats feed). Since bats are nocturnal mammals, much of the survey work is completed during the hours of darkness using acoustic technology (bat detectors).

A bat survey generally involves the following:

  1. Daytime surveys to identify potential roosting sites, potential commuting routes and potential feeding areas. Signs of bat usage of buildings and trees as resting sites include bat droppings and staining. Direct searching for roosting bats can be undertaken using endoscopes and torches.
  2. Night-time survey, undertaken in the appropriate season and during fine, dry weather conditions, is completed using bat detectors, an instrument that detects the echolocation calls of flying bats and allows the observer to identify the species of bat (See What is Acoustic Monitoring?).

Depending on the proposed project, different levels of surveying is completed. For many sites, a one night survey (dusk and dawn surveys) is appropriate.




Bat Activity Detector Surveys















Hibernation Roost Surveys

Spring Roost Surveys

Summer Roost Surveys

Autumn Roost Surveys

Hibernation Surveys

What is Acoustic monitoring?

Bats are not blind but as a nocturnal mammal they rely on a type of sonar to hunt and orientate in the hours of darkness. This sonar is known as echolocation and each bats species produces unique calls that allows Bat Eco Services with the aid of bat detectors to identify the bat species present during a survey.

Bat Eco Services uses a number of different types of bat detectors depending on the type of survey being undertaken and level of data required.

Pettersson D240x Time Expansion/Heterodyne bat detectors are used from Dusk & Dawn Bat Surveys and for Foot-Based Detector Surveys.

Anabat SD1 Frequency Division detectors and Song Meters are deployed during passive monitoring (i.e. detector is left in the field, there is no observer present and bats which pass near enough to the detector are recorded and their echolocation calls are store for later analysis). This is supplemented using BatPods for commuting route monitoring and Tranquility Transect Time Expansion Bat Detectors for roost monitoring.