Scientific name: Halichoerus grypus
Size: Can grow to 2m
Distribution: More than half of the worlds grey seal population lives and breeds around the U.K. coast. The largest populations are found on the Farne Islands, the Cornish coast and Strangford Lough in Northern Ireland.
Months seen: All year round
Life span: Females approx 20 years, males approx 35 years
Habitat: Rocky coastline
Food: Fish, sandeels, and crustaceans
Special features: Male (bull) grey seals are the largest mammals found in the UK. They can weigh twice that of our largest land mammal, the red deer.
Grey seals differ in appearance from the common seal in that they have a longer muzzle.  The colour of the fur varies from brown to silver grey, often with darker blotches.
Grey seals can dive to a depth of over 60 metres. On average they dive for around eight minutes, but they are able to stay underwater for up to thirty minutes before coming up for air. They can swim at speeds of up to 20kph.
Grey seals often sleep at sea, with their noses bobbing out of the water like upright bottles. It's thought they only sleep for around 90 seconds at a time.
The females (cows) give birth to their pups between September and December. At birth, the seal pups weigh around 15kg.
The milk produced by their mothers is almost 60 per cent fat. The pups drink about 3 litres a day and their weight increases rapidly. They put on about 35 to 40kg in their first 3 weeks. At the same time the mothers lose around 70 to 80kg.
Almost as soon as the pups are weaned the males attempt to mate with the females again. Fights often break out between males over the right to females within a certain territory. Dominant males can mate with up to ten females in season.
Since they are the third rarest seal in the world, grey seals are protected during the breeding season by law, from September 1st to December 31st.
Good places to see Grey Seals include The Farne Islands, the Northumberland coast, Cardigan Bay and the Cornish coast.