Gray Seal (Halichoerus grypus)

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For other uses, see Grey Seal (disambiguation).

Grey seal
Grey seal with dark spots touches its nose to a white seal pup.
Female with pup on Horsey Beach, England
Large dark brown seal with long, sloped snout.
Male in Donna Nook, England
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Parvorder: Pinnipedia
Family: Phocidae
Subfamily: Phocinae
Tribe: Phocini
Genus: Halichoerus
Nilsson, 1820
Species:
H. grypus
Binomial name
Halichoerus grypus
(O. Fabricius, 1791)
Grey seal range[1]

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 Atlantic seal or the horsehead seal.[2][3]

Taxonomy

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There are two recognized subspecies:[4]

Image Subspecies Distribution
see caption. Halichoerus grypus grypus Fabricius, 1791 Baltic Sea
see caption. Halichoerus grypus atlantica Nehring, 1886 western North Atlantic stock (eastern Canada and the northeastern United States), the eastern North Atlantic stock (British Isles, Iceland, Norway, Denmark, the Faroe Islands, and Russia)[5]

The type specimen of H. g. grypus (Zoological Museum of Copenhagen specimen ZMUC M11-1525, caught in 1788 off the island of Amager, Danish part of the Baltic Sea) was believed lost for many years, but was rediscovered in 2016, and a DNA test showed it belonged to a Baltic Sea specimen rather than from Greenland, as had previously been assumed (because it was first described in Otto Fabricius' book on the animals in Greenland: Fauna Groenlandica). The name H. g. grypus was therefore transferred to the Baltic subspecies (replacing H. g. macrorhynchus), and the name H. g. atlantica resurrected for the Atlantic subspecies.[6]

Molecular studies have indicated that the eastern and western Atlantic populations have been genetically distinct for at least one million years, and could potentially be considered separate subspecies.[7]

In 2022, overlap in the range of the two subspecies was recorded for the first time. This brings the possibility that hybridisation may occur. As of 2026, no hybrids have been reported.[8]

Description

[edit]
Smaller cream-coloured seal, left, and larger, dark brown, wrinkled seal, right.
Female (left) and male (right), displaying difference in colour and snout shape, Horsey Beach, England
Small, solid grey-coloured seal.
A yearling of ambiguous sex
Cream-coloured harbour seal with a short snout, left, and grey-coloured grey seal with a long snout, right.
A harbour (or "common") seal (left), and a grey seal (right). Note the difference in snout length

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.[9][10][11] 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).[9][12][13]

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.[14][15]

Differences from other seals

[edit]

Grey seals lack external ear flaps (as with their fellow earless seals), and characteristically have large snouts, often referred to as a "Roman nose".[16][17]

The Harbour seal occurs across the entire range of the grey seal,[18] and they can be difficult to tell apart. Compared to the harbour seal, the grey seal has a longer, more sloped snout, a flatter head, and eyes which are set farther apart. The nostrils of the harbour seal form a "V" shape, appearing to meet at the bottom, while the nostrils of the grey seal are more parallel. The grey seal has fewer, larger spots than the harbour seal. Grey seals are often larger than harbour seals, and are about 3 times heavier.[19][17][20]

Wintering hooded seals can be confused with grey seals as they are about the same size and somewhat share a large-nosed look. They can be distinguished by the fact that the hooded seal has a paler base colour and usually evidences a stronger spotting.[21]

Distribution and habitat

[edit]
Seal head poking out from the sea.
A juvenile swimming in the Farne Islands, UK

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.[1]

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%).[22]

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.[23][24][25] 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.[26] 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.[27]

In the German Bight, colonies exist off the islands Sylt, Amrum and on Heligoland.[28]

In Canada, the grey seal is typically found in large numbers in the coastal waters of the Maritime Provinces. It is typically seen in areas such as the Gulf of St. Lawrence, Newfoundland, Prince Edward Island, and Quebec. The largest colony in the world is on Sable Island, Nova Scotia, with an estimated 76,600 pups born in 2021.[29]

In the US, it is found year-round off the coast of New England, in particular Maine and Massachusetts. There are colonies all along the northern Atlantic coast as far south as New Jersey, and occasional sightings have been reported as far as North Carolina.[30] Archaeological evidence confirms grey seals in southern New England with remains found on Block Island, Martha's Vineyard, and near the mouth of the Quinnipiac River in New Haven, Connecticut, and there is a report by Farley Mowat of historic breeding colonies as far south as Cape Hatteras, North Carolina.[3][31] Its range is expanding south, with a growing population in North Carolina.[32]

A group of seals, some grey, some brown, and some cream, in various shades.
A large colony at Nantucket National Wildlife Refuge, Massachusetts, USA. Note the wide variety of colours

During the winter months, grey seals can be seen hauled out on rocks, islands, and shoals not far from shore, occasionally coming ashore to rest. In the spring, recently weaned pups and yearlings occasionally strand on beaches after becoming separated from their group.

A group of seals on the beach.
Group of grey seals on sands at Stiffkey, Norfolk
Local population numbers of Grey seal[14]
Region Pups born annually Year
Canada (total) 98,200 2021[29]
Canada, Sable Island 76,600 2021[29]
UK (total) 57,000 2012
UK, Scotland 50,000 2012
Canada, Gulf of St Lawrence 16,900 2021[29]
Europe (total, excluding UK) 10,700 n/a
UK, Northeast England 4,900 2012
Baltic Sea 4,700 2007
United States 2,600 2008
Ireland 2,100 2012
Norway 1,300 2008
Iceland 1,200 2002
Russia 800 1994
Wadden Sea 600 2014
Total 168,500 n/a

Behaviour and ecology

[edit]
Smaller cream-coloured seal, left, and larger, brown, wrinkled seal, right, laying on the sand together.
Female (left) and male (right) mating, Donna Nook, England
Small cream-coloured seal pup with silky fur.
Seal pup a few days after birth, Heligoland, Germany
Pure white seal pup.
Pups are often a stark white at birth. They shed their entire coat after about a month, and their new coat is much darker

Reproduction

[edit]

Grey seals are capital breeders; they forage to build up stored blubber, which is utilised when they are breeding and feeding their pups, as they do not forage for food at this time. They give birth to a single pup every year, with females' reproductive years beginning as early as 4 years old and extending up to 30 years of age. All parental care is provided by the female. During breeding, males do not provide parental care but they defend females against other males for mating.[33] The pups weigh around 14 kg (31 lb) at birth.[34] They are born in autumn (September to December) in the eastern Atlantic and in winter (January to February) in the west, with a dense, soft silky white fur; at first small, they rapidly fatten up on their mothers' extremely fat-rich milk. The milk can consist of up to 60% fat.[34] Grey seal pups are precocial, with mothers returning to the sea to forage once pups are weaned. Pups also undergo a post-weaning fast before leaving the land and learning to swim.[35] Within a month or so they shed the pup fur, grow dense waterproof adult fur, and leave for the sea to learn to fish for themselves.

Seal pup first-year survival rates are estimated to vary from 80 to 85%[36][37] to below 50%[38] depending on location and conditions. Starvation due to difficulties in learning to feed appears to be the main cause of pup death.[38]

Male grey seals engage in aggressive sexual behaviour, which can lead to severe injuries and even death for the female. Sometimes they will also target females from other seal species.[39] In the North Sea, multiple cases were recorded of pregnant harbour seals dying as a result of forced copulation with male grey seals.[40]

Communication

[edit]

While it was originally understood that marine mammals communicate vocally, new research conducted by researchers at Monash University shows that grey seals clap their flippers as another form of communication. They clap their flippers underwater to deter a predator from attacking. If done during the mating season, the clapping can be used as a way to find a potential mate. The Monash researchers point out that seals are typically known for clapping, so this behaviour may not be a surprise, but the clapping we know typically occurs in captivity. Clapping seals are associated with aquariums and zoos, but were never observed in the wild for this behaviour. They were astonished at how loud these marine mammals were able to clap underwater, but it is logical for the reasons they do this.[41]

Diet

[edit]
Illustration of the relations between the grey seal and its prey.
Grey seal food web in the Baltic Sea[42]
Grey seal on a wooden pier, being fed a fish by a zookeeper.
Captive grey seal being fed, showing snout shape

The grey seal feeds on a wide variety of fish, mostly benthic or demersal species, taken at depths down to 70 m (230 ft) or more. Sand eels (Ammodytes spp) are important in its diet in many localities. Cod and other gadids, flatfish, herring,[43] wrasse[44] and skates[45] are also important locally. However, it is clear that the grey seal will eat whatever is available, including octopus[46] and lobsters.[47] The average daily food requirement is estimated to be 5 kg (11 lb), though the seal does not feed every day and it fasts during the breeding season.

Observations and studies from Scotland, The Netherlands, and Germany show that grey seals will also prey and feed on large animals like harbour seals and harbour porpoises.[48][49][50] In 2014, a male grey seal in the North Sea was documented and filmed killing and cannibalising 11 pups of his own species over the course of a week. Similar wounds on the carcasses of pups found elsewhere in the region suggest that cannibalism and infanticide may not be uncommon in grey seals. Male grey seals may engage in such behaviour potentially as a way of increasing reproductive success through access to easy prey without leaving prime territory.[51][52]

In 2026, a number of instances of grey seals being recorded hunting, killing and partially eating common dolphins (Delphinus delphis) off the coasts of Devon and West Wales, as well as in the Irish Sea, were recorded. It is currently not known why the seals are hunting dolphins; however, it has been theorised that the attacks may be the work of a single population or family of seals operating between North Devon and the Welsh coastline. The seals may also be shifting from hunting harbour porpoises to common dolphins due to the latter species undergoing a significant population increase, becoming the most common species of cetacean in the area where the attacks are taking place.[53]

Predators

[edit]

Grey seals are vulnerable to the typical predators of seals; their primary predator is the orca. Certain large species of sharks are known to prey on grey seals in North American waters, particularly great white sharks and bull sharks. Some grey seal carcasses have washed ashore with visible "cookie cutter" bite marks, a telltale sign of attack by a Greenland shark.[54][55] In the waters of Great Britain, grey seals are a common prey species for orcas.[56][57] In the Baltic, grey seal pups are prey for White-tailed eagles and Great black-backed gulls.[1]

Relationship with humans

[edit]
Black-and-white image of a seal tied to a plank of wood.
A hunted grey seal, 1961, Finland

Hunting and culling

[edit]

Grey seals were nearly extirpated in the United States from hunting for oil, meat, and skins. Bounties were paid on all kinds of seals up until 1945 in Maine and 1962 in Massachusetts.[58] In 2013, there were calls by fishermen in Cape Cod to cull the rising grey seal population, over concerns it was harming the local cod catch.[59]

In 2012, there was a controversial suggestion to cull 70,000 grey seals in the Gulf of St. Lawrence. This was spurred by predictions that the local cod population would be extirpated, with the primary cause attributed to grey seals. However, as of 2026, no such cull has taken place.[60][61]

As of 2026, grey seal hunting is legal in all countries on the Baltic Sea. In 2026, the quota for grey seals in Sweden was 1,350 — up from 1,000 the previous year.[62]

Seal hunting is not a common practice in the UK,[63] where it is illegal to kill seals.[64] However, licenses can be granted for culling in specific circumstances. Culling regulations in the UK as a whole are governed by the Conservation of Seals Act 1970, however each individual region can decide its own laws. In England, Wales, and Scotland, licenses to cull seals can be granted to protect flora and fauna, to reduce population surplus, and to protect public safety.[65] In 2021, the Marine (Scotland) Act was amended, which repealed the ability to grant licenses for prevention of damage to Scottish fish farms.[66] In Scotland, 62 grey seals were legally shot under license in 2020.[67]

In 2022, the Cornish Mackerel Fishermen group called for a cull in Cornwall, referring to grey seals as "rats of the sea". This was met with heavy backlash from marine conservation groups.[68]

Conservation and recovery

[edit]
A short video on monitoring and conservation of grey seals on Skomer Island, Wales

After near extirpation in the United States, sightings began to increase in the late 1980s.[58] One year after Congress passed the 1972 Marine Mammal Protection Act preventing the harming or harassing of seals, a survey of the entire Maine coast found only 30 grey seals.[58] At first grey seal populations increased slowly but then rebounded from islands off Maine to Monomoy Island and Nantucket Island off of southern Cape Cod. The southernmost breeding colony was established on Muskeget Island with five pups born in 1988 and over 2,000 counted in 2008.[69] According to a genetics study, the United States population has formed as a result of recolonisation by Canadian seals.[69] By 2009, thousands of grey seals had taken up residence on or near popular swimming beaches on outer Cape Cod, resulting in sightings of great white sharks drawn close to shore to hunt the seals.[70] A count of 15,756 grey seals in southeastern Massachusetts coastal waters was made in 2011 by the National Marine Fisheries Service.[30] In 1997, a grey seal was recorded for the first time in North Carolina.[32] Grey seals are being seen increasingly in New York and New Jersey waters.[30]

The population in the Baltic Sea increased about 8% per year between 1990 and the mid-2000s, with the numbers becoming stagnant since 2005. Some anthropogenic causes of death include drowning in fishing gear and hunting.[71]

Human noise pollution continues to affect marine-life communication but remains an understudied facet of marine conservation efforts. In more recent years, the potential negative effect of human noise has been highlighted with the discovery of seals using clapping as a form of communication.[41] In Northern Ireland, it is illegal to intentionally or recklessly disturb a seal.[72]

In captivity

[edit]

Grey seals are adaptable to life in captivity, and are commonly found as zoo animals around their native range, particularly in Europe.[73] Grey seals need a minimum of 30 m2 (320 sq ft) land area and 120 m2 (1,300 sq ft) pool area with a minimum depth of 2.3 m (7 ft 7 in). Caution needs to be taken when handling grey seals, as they are capable of delivering strong bites.[74]

References

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