20-7-2026 FOTA WILDLIFE PARK, IRELAND - GREY SEAL (Halichoerus grypus)

The grey seal (Halichoerus grypus), or gray seal in the United States, is a large seal of the family Phocidae, which are commonly referred to as "true seals" or "earless seals". The only species classified in the genus Halichoerus, it is found on both shores of the North Atlantic Ocean. In Latin, Halichoerus grypus means "hook-nosed sea pig". It is also known as the horsehead seal, owing to its large head.

The grey seal is large and heavy, with individuals from the eastern Atlantic being 1.6–2.3 m (5 ft 3 in – 7 ft 7 in) long and weighing 100–310 kg (220–680 lb), while individuals from the western Atlantic are up to 2.7 m (8 ft 10 in) long, and can reach a weight of as much as 400 kg (880 lb). It is found widely across the northern Atlantic, ranging from the US to Russia, and occasionally as far south as Portugal. It can be divided into two subspecies: the Baltic grey seal (Halichoerus grypus grypus), found in the Baltic Sea, and the Atlantic grey seal (Halichoerus grypus atlantica), found everywhere else. The largest populations are in Canada and the UK.

Grey seals have a varied diet, feeding mostly on fish, and occasionally on invertebrates such as octopuses and lobsters. Their main predators are orcas, and they are also prey to sharks. The pups are preyed upon by eagles and gulls.

A yearling of ambiguous sex — juveniles are often a solid colour, and can be difficult or impossible to sex

The grey seal is large and heavy: In the eastern Atlantic, males are typically 1.95–2.3 m (6 ft 5 in – 7 ft 7 in) long and weigh 170–310 kg (370–680 lb); the females are much smaller, typically 1.6–1.95 m (5 ft 3 in – 6 ft 5 in) long and 100–190 kg (220–420 lb) in weight. Individuals from the western Atlantic are often much larger, with males averaging up to 2.7 m (8 ft 10 in) and reaching a weight of as much as 400 kg (880 lb) and females averaging up to 2.05 m (6 ft 9 in) and sometimes weighing up to 250 kg (550 lb). Record-sized bull grey seals can reach about 3.3 m (10 ft 10 in) in length. A common average weight in Great Britain was found to be about 233 kg (514 lb) for males and 154.6 kg (341 lb) for females whereas in Nova Scotia, Canada, adult males averaged 294.6 kg (649 lb) and adult females averaged 224.5 kg (495 lb).

Colours and patterns are highly variable. Males tend to have a light pattern on a dark background, while females tend to have the opposite — a dark pattern on a light background, often with a noticeably light belly. The neck and chest of males tend to be wrinkled and scarred, while females are smoother. Males have an especially wide muzzle. Males have a large, visible opening on the lower abdomen, while females have no obvious openings. Juveniles are often a solid colour, and can be difficult or impossible to sex. About 1 in 400 seal pups are melanistic, where they have a solid black coat.

The grey seal is resident to 18 countries: Belgium, Canada, Denmark (including Faroe Islands), Estonia, Finland, France, Germany, Iceland, Ireland, Latvia, Lithuania, the Netherlands, Norway, Poland, Russia, Sweden, the United Kingdom, and the United States of America. It is also an occasional vagrant in Greenland and Portugal. The global population was estimated to be about 632,000 in 2016.

In the UK, the most ecologically significant breeding grounds, classified as Special Areas of Conservation (SACs) Grade A/B, are as follows (percentage of annual UK pup production in parentheses): Monach Islands, Outer Hebrides (20%); Faray and Holm of Faray, Orkney (9%); North Rona, Outer Hebrides (5%); Isle of May, Fife (4.5%); Treshnish Isles, Inner Hebrides (3%); Berwickshire and North Northumberland Coast (2.5%); and Pembrokeshire Marine (2%).

Some of the more touristically significant breeding grounds in the UK which aren't SACs include: Blakeney Point and Horsey Beach in Norfolk, various locations in Cornwall, and Donna Nook in Lincolnshire. Large numbers of grey seals have recently commenced a recolonisation of the tidal section of the River Thames in London; a survey conducted by the ZSL in 2024 found that around 3,000 grey seals were living in the area.[24] In Ireland, the 5 largest colonies are in order: Inishkea Islands, County Mayo; various islands in Connemara, County Galway; various islands in County Donegal; Blasket Islands, County Kerry; and Saltee Islands, County Wexford.