Smooth snakes are the rarest reptile in Britain, found only on lowland heathland in southern England. Habitat loss and fragmentation have reduced their distribution to isolated populations highly vulnerable to local extinction.
Smooth snake populations in small fragmented heathland patches face inbreeding depression, reduced prey availability, and lack of thermal microhabitats required for thermoregulation. Juveniles born in isolated populations have limited dispersal opportunities. Road mortality removes adults from already-small populations. The welfare of individuals in declining populations is compromised by reduced fitness associated with genetic bottlenecks.