Bat conservation: good practice for conducting surveys

Guidelines for bat surveys

6 July 2016

Morgan Taylor outlines the latest good practice advice from the Bat Conservation Trust on conducting surveys for planning and development

The Bat Conservation Trust (BCT), an NGO concerned with UK bat conservation, recently published the 3rd edition of its good practice guidelines, Bat Surveys for Professional Ecologists.

This document builds on the previous, 2012 version to provide a basis for bat surveying in relation to planning and development by consultant ecologists.

Bats are primarily protected in the UK under the Wildlife and Countryside Act 1981 (as amended) and the Conservation of Habitats and Species Regulations 2010. It is an offence to capture, kill, injure or disturb a bat or to damage, destroy or obstruct its roost. The National Planning Policy Framework and biodiversity action plans also ensure that conservation of bats and their habitat represents a material consideration in the planning process.

There are 18 species of bat in the UK, all of which employ echolocation to navigate and catch their insect prey. Bats provide valuable ecosystem service functions – that is, they participate in natural processes that benefit humans – and act as useful indicator species for the health of our natural environment. But many bat species are threatened by continued loss of roost space, extensive urbanisation and habitat fragmentation and loss.

It is therefore important to consider bats during the development process, both from a planning and legal compliance perspective and with our own best interests in mind. Accordingly, the approach taken in bat surveying is important in any application where suitable habitats could be affected or lost.

Developments often need to consider buildings, structures and trees that have potential value for roosting bats and assess potential impacts on their commuting routes and foraging areas. Foraging and commuting habitats do not necessarily have direct statutory protection and have been subject to less scrutiny.

Guideline updates

Many of the updates to the BCT’s guidelines relate to improved accessibility and clarity for consultants. However, the following key points have been added.

Species core sustenance zones
This defines the areas surrounding a roost where the quality and availability of suitable habitat will stand to influence its status significantly, according to species. This information should be used with care, particularly given the relative paucity of data on some species.

However, it provides a useful basis to assess the impacts on a roost from habitat degradation related to development. These core sustenance zones provide a formal basis for undertaking impact assessments; the implications are that development some distance from known roosts may still have to undertake a robust assessment of the potential impact on that roost and mitigate accordingly.

Bat roost inspection surveys for trees
More robust guidelines have been provided, with one notable change being a reduction in the number of surveys needed for trees that are classed as low value for roosting. Further clarification on where climbing surveys may be used is also provided, building on information from the 2013 Bat Tree Habitat Key document.

Data analysis and interpretation
In many instances, consultants will use the word 'significant' to describe results without scientific analysis to support this conclusion. Data in many cases will now have to be reviewed and statistics used to show the significance of the results. This enables conclusions to be based on statistical inference as well as professional and technical opinion – for example, when comparing the importance of different sites for bats. Bat pass rates can be measured and compared according to the type of site. Being able to conclude that there is statistical significance to the dfference between the relative importance of multiple sites will enable more robust conclusions to be made.


Guidance has to tread a fine line between what is meaningful from a scientific perspective and what can realistically be achieved with respect to the costs, logistics and time frames of planning. It will always come down to the individual ecologist to make the final judgement about what they feel is appropriate and proportionate for each project.

However, guidelines such as these offer an important basis to inform the approach, providing consistency throughout the industry, adding scientific rigour to survey design. They will also continue to be the survey guidelines to which planning officers and interested parties refer when reviewing bat survey reports, making it important to understand what might be required.

Morgan Taylor is Senior Consultant at Greengage

Further information