Bat Winter Hibernation Surveys
Updated: Feb 4, 2020
There are 18 bat species native to the UK and they all hibernate during the winter. The UK’s native bat species are all insectivorous, meaning they exclusively feed on insects. Bats hibernate when insects become scarce, due to the cold weather, in order to conserve their energy. Bats can hibernate anytime from October to March, but their core hibernation period is from December to February. Bats need to hibernate in places that have a stable low temperature, high humidity, are safe from predators and safe from disturbance. Typical hibernation site for bats include caves, tunnels and trees; however, bats do often hibernate in buildings, particularly in cellars, abandoned buildings and in wall crevices.
Typically, bats will have several different roosts and rotate between them throughout the year. However, it has been documented that some species, particularly common pipistrelles, soprano pipistrelles and brown long-eared bats, will also use their summer roosts as hibernation roosts. Ecologists should consider the hibernation potential of buildings when conducting a preliminary inspection for bats. More information on preliminary inspection for bats can be found here. Therefore, it may be necessary to conduct hibernation surveys of a building, particularly if the building has already been assessed as a confirmed summer roost.
Bat hibernation surveys should be conducted by an ecologist who holds at least a Class 2 bat survey licence. The building is inspected internally for hibernating bats and signs of hibernating bats, such as faeces and feeding remains during January and February. All cracks and crevices are inspected with an endoscope and torch. Static bat detectors are also deployed over three visits during December, January and February. The detectors are left in place for at least two weeks on each visit. If hibernating bats are present, the detectors may pick up bat ‘chattering’ or echolocation calls, if the weather is mild and bats briefly come out of hibernation to feed or move around.
Here at aLyne Ecology, we have ecologists who hold a Class 2 bat licence and are experienced in conducting Bat Winter Hibernation Surveys. For more information, please contact us.
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