Bat roosts in buildings and trees provide essential maternity and hibernation sites whose disturbance or destruction causes welfare harm to protected bat populations.
Bat roost disturbance welfare primarily affects breeding females and their pups. A disturbed maternity roost colony may relocate, but if pups are present, they cannot fly and may be left behind - causing death from hypothermia or starvation. Individual bats disturbed from hibernation in winter expend critical fat reserves warming up - repeated disturbance causes progressive emaciation and death. The destruction of a roost through renovation or demolition may cause the death of any bats present through direct trauma, exposure, or inability to access the roost site. Given that bats raise only one pup per year, roost disturbance can have population-level effects through reduced recruitment.