To cope with the lack of insects present during winter bats are able to hibernate. They can survive for months on the fat stores they have built up during the summer. During October bats seek suitable hibernation sites, and begin periods of torpor. Bats choose these sites (often called hibernacula) to provide the optimum environment for their hibernation.

Bats often hibernate in disused buildings, old trees or caves, where the temperate is generally below 10°C and remains constant. Hibernating is a state of inactivity characterised by a lower metabolic rate, slower breathing and a drop in body temperature almost to that of the surrounding environment. Once they have entered hibernation they are defenceless against danger, as it takes half an hour or more for a bat to revert back to its normal alertness after being woken. Bats continue to hibernate throughout winter until the weather warms in March / April, when they begin to come out of hibernation and are hungry and active.

Bats are protected by UK and European legislation therefore any action or development which has the potential to impact on bats or their habitats must be carried out under a European Protected Species (EPS) licence issued by Natural England. Bat surveys must be conducted to provide information on the type and number of bats which will be affected, how the bats use the site and what impact your development will have on any bats using the area.