Seals and Porpoises
Ramsey is host to one of the largest breeding colonies of Atlantic Grey seals in the British Isles. Throughout most of the year there is a relatively small population of around 100 seals in the waters around the island, however, twice annually these numbers will increase significantly as the mammals come to the area, to moult in February/March and to breed in late August through to November. During the breeding season in particular, numbers may increase to just under a thousand seals.
The seals give birth to their pups on the beaches around the island and will feed those pups for three to four weeks, in which time the pup will triple its birth weight as the female, who does not feed herself whilst feeding the pup, rapidly loses condition. The pups are born with a white fluffy non waterproof coat which they will moult out in their fourth week when they are weaned. During these first few weeks of life the pups spend very little time in the water, as they are not good swimmers at this stage and initially do not have sufficient body fat to keep them warm in the sea.
They will however be encouraged into the water by the mother towards the end of this period when they will be given “swimming lessons”. Once they have been weaned they are abandoned as the mother will head out to sea to start feeding again to build up the fat reserves she has used up feeding the pup. The pup is left to fend for itself and this includes learning to catch its own food. During the first couple of months the pups are very vulnerable to bad weather which is the main cause of fatalities amongst them.
The average life span of an Atlantic grey seal is between 25 and 35 years old. Generally the females will live for 5-10 years longer than the males. This is probably largely to do with the fact that during the breeding season they will breed on a harem basis whereby an adult bull will hold a territory with as many as 8 breeding females. They will defend this territory ferociously from any other bull seals, fighting for the right to mate with the female which will happen when she has weaned the pup. A bull seal therefore will spend much of his time fighting during the breeding season, and as he is unwilling to leave the territory unprotected for any length of time he will not feed very much.
Porpoise are one of the smallest members of the Whale and dolphin family, reaching a max. of 1.7m and there is a resident population of Common or Harbour porpoise in the area of Ramsey Sound. They are tidal feeders and, as such, their habits are relatively predictable. They tend to feed on the Ebb tide to the south of Ramsey Sound while the flood tide will find them north of St. Davids Head. The reason for these feeding patterns is that the Sound in the middle drops off to 80 metres deep in a deep underwater canyon whilst at either end it shallows.
When the tide hits these shallower waters to the north and south depending on its direction it scours up the sea bed bringing nutrients to the surface which attract fish to the area, in turn attracting the porpoises. They hunt using echolocation and diving for up to five minutes, and though relatively slow swimmers can cover hundreds of miles in a few days. Unlike their cousins the dolphins, they are shy creatures and whilst they tolerate the boats they take no interest them and will not bow-ride.