The British population of Harbour Seal has fluctuated greatly over recent decades, but, helped by an exponential increase on the near continent, it is currently on the rise in parts of its range. Stephen Westcott describes the spread of this species in the English Channel and the prospects for colonisation of south-west Britain.
Only two species of seal live and breed in British waters: the Grey Seal Halichoerus grypus and the Harbour Seal Phoca vitulina (known also as the Common Seal). The Grey Seal occurs only in the north Atlantic, while the Harbour Seal has a circumpolar distribution across the northern hemisphere, stretching as far south as subtropical waters.