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Bats


ECOSA carry out a range of surveys for all species of bat. These surveys include the assessment of trees and buildings for their potential to support roosting bats; surveys to confirm the presence and status of a roost, and to identify key foraging and commuting habitat. Our project experience includes numerous bat emergence/roosting and activity surveys for proposed developments, including renewable energy projects (wind turbines), roads, housing developments, hospitals, schools and private homeowner extensions and loft conversions.

Using our survey data to devise appropriate mitigation strategies, we have successfully attained many Natural England licences for development works affecting bat roosts. Mitigation works range from the incorporation of bat roost features within new buildings to the design of dedicated bat roosts.

Our ecologists hold Natural England and Countryside Commission for Wales, bat licences and are experienced in the supervision of tree felling and pre-demolition building searches.

For further details on bat ecology, legal protection and survey methods, please see links below.

British Species and Ecology

There are a total of 17 species of bat resident in Britain plus a number of others that have only been recorded as occasional visitors to the UK.

The majority of bats are active between April or May and October depending on the weather conditions. Bats roost in a wide range of locations; typical sites include trees with loose bark, holes and cracks and perhaps more commonly in buildings. Building roosts maybe in barns, older traditional style buildings and modern houses. Typical roost sites in buildings include roof spaces, soffit boxes, behind hanging tiles and under loose lead flashing. Bats may enter these roost spaces through very small gaps that may not be evident to the non-specialists.

Protection Under UK Legislation

In England, all bats are fully protected under the Wildlife and Countryside Act 1981, through inclusion in Schedule 5, and under the Conservation (Natural Habitats, &c.) Regulations 1994, which implements the EC Habitats Directive 92/43/EEC in the United Kingdom.

Taken together, these legislative instruments make it illegal to carry out the following activities:

  • Deliberately or recklessly capture or kill bats;
  • Deliberately or recklessly disturb bats;
  • Damage or destroy a bat breeding site or resting place; and
  • Keep, transport, sell or exchange, or offer for sale or exchange, any live or dead bat, or any part of, or anything derived from a bat.

Any activity that would result in a contravention of the above legislation would require a Natural England licence to avoid committing an offence.

Survey Methods

Bat surveys must be carried out by licenced surveyors, if there is a possibility of disturbing roosting bats. ECOSA surveyors hold current Natural England bat licences for England and Wales. Survey methods for bats consist of two phases, which apply to both trees and buildings:

Phase 1 Surveys

Phase 1 surveys consist of an evaluation of the structure of a building or features of a tree to determine their suitability for roosting bats. For example features such as loose bark on trees or gaps between tiles may provide roosting opportunities for bats. Phase 1 surveys will often need to be followed by Phase 2 surveys if evidence of roosting bats or features suitable for roosting bats are recorded or identified.

Phase 2 Surveys

Phase 2 surveys involve a detailed assessment of the status of a roost site or potential roost site. If the Phase 1 survey confirm the presence of a bat roost then Phase 2 surveys will be essential in providing sufficient information for a Natural England licence. Phase 2 surveys will usually involve the use of bat detectors to determine the species present within a roost, these are combined with counts. This accurate assessment is essential for bat licencing purposes. ECOSA use Pettersson 240x time-expansion detectors which slow down the echolocation made by bats (usually by 10x). This enables a recording to be made which can be downloaded into analysing software. Once the recording is opened within the software it is displayed as a sonogram and from this it is possible to analyse parameters of the echolocation such as its peak frequency, duration and time between calls allowing species identification.

Survey Timing

Phase 1 surveys can be carried out throughout the year, but will almost invariably lead to Phase 2 surveys which are carried out between late May and early September. At this time bats occupy summer roost sites and the status of a roost can be reliably assessed.

Mitigation

Mitigation for the loss of a bat roost is a requirement of a Natural England licence. The amount and type of mitigation for the loss of a bat roost will be dependant on the status of the roost. For smaller low status roosts the provision of bat boxes in trees or on buildings or the provision of bat roosting units in buildings may be sufficient. For higher status roosts such as maternity roosts the construction of dedicated bat roosts may be necessary. ECOSA has a wide experience in advising on and implementing suitable mitigation strategies.

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