‘Grey’ is not the most inspiring of names for the larger of the two seal species found in UK waters. It may be accurate in terms of general colourisation, but there are spots and subtle mottling that give each seal a unique appearance. That said, given that the literal translation of the Latin name Halichoerus grypus is ‘hook-nosed sea-pig’, perhaps grey seal is not so bad.
How big are grey seals?
The sloping, horse-like shape of the head is a key distinguishing feature of the grey seal, not least when the bobbing head of the animal is all that can be seen. When hauled out on rocks, however, while either basking or gathering to breed, the size of a grey seal becomes apparent.
A male, or bull, may measure more than 2.5 metres long and weigh in excess of 300 kg, while females are typically around two-thirds the size.
Grey seals might be seen anywhere along the coastline of the British Isles, although numbers are higher in the west and north, with a high concentration in the western and northern Isles of Scotland.
Estimates of the total UK population range from 112,000 to 180,000, representing between 35% - 50% of the global population. They are found across the Northern Atlantic, with animals on the US and Canadian coasts larger than their eastern cousins.
What do grey seals eat?
Fish comprise the bulk of a grey seal’s diet, although they will exploit whatever source is most abundant including octopus, squid and crabs. Just before a dive, the seal will slow its heart rate so as to conserve oxygen levels in the blood and this enables dive times of between 4-8 minutes, with a maximum recorded time of 30 minutes. They can swim at speeds of 15.5mph (25km/h) and dive to 300 metres, although they typically feed in depths of up to 70 metres.
Grey seals spend around 80% of their life in the water but have regular ‘haul-out’ spots on small islands or secluded shorelines and large, communal pupping areas which may be used year after year. Adult seals have few natural predators, with orca the only realistic threat to adults in UK waters.
The pups, which are white and fluffy when born, are at risk from white-tailed eagles or great black-backed gulls, but have a relatively high survival rate, between 50% and 80%, and human activity often presents a greater impact than natural predation.
How long do grey seals live?
Cows give birth to single pups and shortly after they have weaned, they will mate once more. The fertilised egg will lay dormant for up to three months as the female builds fat reserves in order to carry the foetus to term, and she will return to the pupping grounds the following autumn or early winter. A cow might live for 30 years, so despite only producing a single pup each year, individual animals might parent 20 or more in a lifetime.
Top image: A grey seal pup and its mother near the Lincolnshire Wildlife Trust's Donna Nook nature reserve. The seals return to the North Sea in January before returning to the same area to give birth the following year. The Donna Nook reserve is the UK's premier destination to see Grey Seals. (Credit: Dan Kitwood/Getty Images)
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