Bechstein's bat is one of the UK's rarest mammals, entirely dependent on ancient woodland with abundant tree cavities. It is a welfare indicator species for old-growth woodland quality.
Bechstein's bats are particularly sensitive to woodland management practices. Felling of old trees with cavities destroys irreplaceable roost sites — maternity colonies typically occupy 20+ different roosts within a territory, switching between them regularly. Pesticide use in adjacent farmland reduces the beetle and moth populations on which they feed. Road lighting near woodland fragments foraging habitat — Bechstein's bats are light-averse and will not cross illuminated gaps. Installing bat boxes near ancient woodland provides supplementary roost sites and has been shown to support local population recovery.