Bats can be found hibernating in trees between October and May, although this is not a constant hibernation. Changes in temperature or hunger/thirst can arouse bats to feed or to find a new roost, so some may still be active during winter.

Different roosts are used by bats depending on the time of year. Hibernation roosts will be found in the same tree features as summer roosts e.g. cracks, splits, hazard beams, woodpecker holes, loose bark. Therefore, it is important to inspect these features for roosting bats prior to works.

It takes time for bats to fully arouse from hibernation, so disturbance to a roost can cause significant harm as damage may be done before any bats present are able to fly away. Any works to a tree with hibernating bats will almost certainly cause disturbance, and therefore need to be avoided or mitigated against.

  • Always search for potential roost features (e.g. cracks, splits, hazard beams, woodpecker holes, loose bark) on trees at site as part of pre-works checks.
  • Always inspect any potential roost features found for hibernating bats using a suitably qualified ecologist. 
  • If a bat roost is found, a mitigation licence for works to the tree in question must be sought from Natural England. Advice for this process should be obtained from an ecologist. 
  • No works should be undertaken to trees containing bat roost without a licence from Natural England.