Bats are one of the species most frequently associated with ecology and development projects and for those who are involved with development schemes on a regular basis, bat surveys during the spring and summer months are often a standard requirement in order to provide baseline information to inform assessments and development proposals. However, knowledge of bats and bat surveys during the winter months is less widespread. In this post, we are going to take a closer look at bats and development projects over the winter months.


Bat ecology over autumn and winter

In October, bats are in the midst of building up fat reserves, seeking out hibernation sites, and mating (‘pups’ aren’t, however, born until the following June). During periods of cold weather, bats will enter periods of torpor and as temperatures continue to drop over the coming weeks, they will go into hibernation in November/December – lowering body temperature and metabolic rate to conserve energy whilst they live on fat reserves. They will occasionally emerge to feed during the winter months, if temperatures are warm enough.


All bat species and their roosts are currently protected by law; legislation makes it an offence to destroy, damage or block access to a bat roost, or to deliberately or recklessly disturb, injure or kill any bat. The roost is protected whether bats are present or not.


Over winter, bats require different conditions in which to roost compared to during their ‘active’ season during the spring and summer months. Bats can hibernate individually or together during the winter months. Depending on the species of bats, hibernation roosts typically comprise underground sites such as tunnels, caves or basement cellars; tree cavities; and cracks and crevices in buildings.


Winter bat surveys

A preliminary roost assessment by a bat licensed ecologist will identify any potential features on a site that may be used by bats for hibernating. On occasion, evidence such as field signs and live bats may also be identified during a preliminary assessment. Where further survey work is required in order to identify whether bats are using a potential hibernation roost, methods such as the deployment of automated/static bat detectors and specialist cameras are set up and left in the situ to record any bat activity.


Where a hibernation roost is identified, an impact assessment will be undertaken by an experienced ecologist, and the requirement for mitigation (including permanent replacement roost features) and a licence will be determined.


Our bat licensed ecologists at The Ecology Co-op are able to guide you through any winter survey requirements for bats. We are experienced in guiding development through the planning process with regards to considerations surrounding bat presence, mitigation and licensing. If you are proposing to develop a site/undertake work to an existing development, we’re on hand to help, so please get in touch to discuss your project further.