Bat maternity colonies are the most welfare-sensitive bat roosts, housing pregnant females and dependent pups. Protection during this period is critical for population welfare.
Bat maternity colony welfare is concentrated in time and place - disturbance during the 4-6 week critical period causes welfare harm that echoes through the entire colony's reproduction that year. Legal protection of maternity roosts reflects their special welfare significance. Any building work near known maternity roosts requires expert consultation to avoid catastrophic colony welfare harm.