Gray Seal (Halichoerus grypus): Facts, Size and Habitat

What does a gray seal look like?

Gray seals belong to the true seals, or earless seals (family Phocidae). They have no external ear flaps, short front flippers with strong claws, and hind flippers that point backward, so on land they move by hunching along on their bellies. In the water they are powerful, agile swimmers.

The head is the best clue to identity. Gray seals have a long, flat-topped head with a straight or slightly arched profile, often called a Roman nose. It is especially heavy in adult males, which is why Canadians call them horseheads and why the scientific name means “hook-nosed sea pig.” Males also have broad, wrinkled necks and shoulders that are often scarred from fights.

Coat colors vary a lot. Males are usually dark gray, brown or almost black with paler blotches, while females are usually silver-gray or light brown with scattered dark spots and a paler belly. Wet seals look darker than dry ones. Each seal’s pattern is unique, so researchers can recognize individuals from photographs.

In Europe and New England, gray seals share many beaches with the smaller harbor seal. The harbor seal has a short, dog-like snout, a rounded forehead and V-shaped nostrils, while a gray seal’s nostrils sit almost parallel and its face looks longer and more horse-like. On land, gray seals and harbor seals both move like caterpillars, unlike sea lions, which walk on all four flippers.

How big is a gray seal?

Gray seals are among the largest seals of the North Atlantic, and males are much bigger than females. They are often described as the largest wild carnivore in Britain. Seals on the western side of the Atlantic, in Canada and the United States, are generally larger than those in Europe.

According to NOAA, the largest males in the western Atlantic can reach about 3 m (10 ft) and 400 kg (880 lb). Body weight changes a great deal through the year, because seals fatten up before the breeding season and then go weeks without eating. For a closer look at bulls, cows and pups, see How big is a gray seal?

Where do gray seals live?

Gray seals live in cool coastal waters on both sides of the North Atlantic. Scientists usually recognize three populations: the western Atlantic population in eastern Canada and the northeastern United States, the eastern Atlantic population around Iceland, the Faroe Islands, Britain, Ireland, Norway, northwest Russia and the North Sea coasts of Europe, and a separate population in the Baltic Sea. Wanderers occasionally reach Portugal and Greenland, and a small number now live as far south as North Carolina.

The largest single breeding colony in the world is on Sable Island off Nova Scotia, where tens of thousands of pups are born each winter. Britain and Ireland are the other great stronghold, with big colonies in the Outer Hebrides, Orkney, the Farne Islands, the Isle of May, Wales and Cornwall. In recent decades gray seals have also returned to the Wadden Sea coasts of the Netherlands and Germany and to Cape Cod in Massachusetts.

At sea, gray seals feed over the continental shelf and can travel far. Young seals in particular disperse widely after leaving their colony and may travel more than 1,000 km (620 mi). On land they haul out on rocky ledges, islands, sandbanks, beaches and, in the Baltic and the Gulf of St. Lawrence, on sea ice.

What do gray seals eat?

Gray seals are carnivores that eat mainly fish living on or near the seabed. NOAA lists sand eels, hake, whiting, cod, haddock, pollock and flatfish among their main prey, and herring, wrasse and skates are locally important. They also take squid, octopus, crabs, lobsters and occasionally seabirds. Small fish are swallowed whole underwater, while large ones are brought to the surface and torn apart.

On average a gray seal eats about 4–6% of its body weight a day, often estimated at around 5 kg (11 lb) of fish, but it does not feed every day and fasts during the breeding season and the molt. Most dives last a few minutes and reach the seabed in water less than about 100 m (330 ft) deep, but NOAA reports dives as deep as about 475 m (1,560 ft) and as long as an hour.

Some gray seals, mostly large males, also hunt other marine mammals. Studies in Scotland, the Netherlands and Germany have documented gray seals killing harbor porpoises and harbor seals, and males have been seen killing and eating gray seal pups. For more on what seals eat and how they hunt, read What do seals eat?

Behavior and communication

Gray seals spend most of their lives at sea, alone or in loose groups, and come ashore to rest, molt and breed. When hauled out they often lie in a curved “banana” posture with head and tail raised. Large haul-outs can hold hundreds or thousands of seals, especially during the spring molt, when they replace their fur.

They are vocal animals. On land they moan, hiss, snort and make long, wailing calls that carry across beaches, and pups cry with a sound often compared to a human baby. In 2020, researchers published the first video of a wild male gray seal clapping its front flippers together underwater off the Farne Islands, producing a sharp crack that may warn rivals or attract females.

Gray seals are curious and often swim close to boats and divers, but they are wild predators with powerful jaws and should never be approached or fed.

Breeding colonies and pups

Gray seals breed in colonies, also called rookeries, on remote islands, sandy and rocky beaches, caves and, in places, sea ice. Unusually for a seal, the timing of birth depends strongly on location. Pups are born from about September to November in southwest Britain and Ireland, from October to December in much of Scotland, from November to January on England’s east coast, mainly from December to February in eastern Canada and in February and March in the Baltic.

A female gives birth to a single pup, usually within a day or two of coming ashore. The pup wears a thick, creamy-white coat called lanugo and weighs about 11–20 kg (24–44 lb). For roughly 15–21 days it drinks milk that is up to about 60% fat, gaining around 1.5–2 kg (3–4 lb) a day, so that it roughly triples or quadruples its weight. The mother eats nothing during this time and loses a large part of her body weight.

Then she leaves abruptly, usually after mating with a nearby male. The weaned pup sheds its white coat, grows a waterproof adult coat and stays on the beach for up to several weeks, living on its blubber before it goes to sea and learns to fish alone. A lone, fat pup on the beach is therefore normal; see Is a seal pup alone on the beach abandoned?

Males do not help raise pups. On crowded beaches the biggest males try to stay among the females and mate with as many as they can, fighting rivals and fasting for weeks. Pregnancy lasts about 11 months, including a delay of roughly three months before the embryo implants, which allows each female to give birth at the same season every year. Females usually have their first pup at about 4–6 years old, while males rarely breed successfully before about 8–10 years.

How long do gray seals live?

Gray seals usually live about 25–35 years in the wild, according to NOAA. Females tend to live longer than males, which wear themselves out in the competition for mates. The oldest known wild female was about 46 years old.

Many pups never reach adulthood. First-year survival varies widely by colony and year, from about 80% in good conditions to less than half in bad ones, and starvation while learning to hunt is a major cause of death.

Predators and threats

Adult gray seals have few natural predators. Orcas hunt them around Britain and elsewhere in the North Atlantic, and great white sharks hunt them off Cape Cod, where the seal recovery has drawn sharks close to beaches in summer. In the Baltic, white-tailed eagles and great black-backed gulls take some young pups, and winter storms can wash pups off their beaches.

People were long the main threat. Gray seals were hunted for skins and oil and killed as competitors by fishers, and bounties paid in Maine until 1945 and in Massachusetts until 1962 almost wiped them out in the United States. In the Baltic, hunting and pollution with PCBs and DDT in the 20th century cut numbers to only a few thousand and left many females unable to breed.

Today the main threats are entanglement in fishing nets and marine debris, chemical contaminants, oil spills, vessel strikes and disturbance. Conflict with fisheries continues, and controlled hunting or culling is still allowed in some countries, including around the Baltic Sea and in Norway.

Conservation status

The IUCN Red List lists the gray seal as Least Concern, with an estimated world population of about 632,000 in 2016. Most populations have grown strongly since legal protection in the 1970s.

In Canada, the population grew for decades to an estimated 366,000 or so in 2021, although growth has slowed. Off New England, a survey in the early 1970s found only about 30 gray seals along the whole Maine coast, but gray seals then recolonized islands such as Muskeget and Monomoy, and many thousands now live off southeastern Massachusetts. Baltic numbers have recovered from the pollution era to tens of thousands. Britain holds well over 100,000 gray seals, protected under the Conservation of Seals Act 1970 and later laws.

Watching gray seals without disturbing them

Gray seal colonies are one of the great winter wildlife sights of Britain. Well-known places include Donna Nook in Lincolnshire, Horsey and Blakeney Point in Norfolk, the Farne Islands, the Isle of May, and Ramsey and Skomer islands in Wales. In North America, boat tours from Chatham on Cape Cod visit large haul-outs.

The key rule is distance. Disturbed seals stampede into the water, mothers can be separated from pups, and dogs off the leash are a particular problem. NOAA advises staying at least 50 yards (46 m) from seals in the United States, and many British colonies use fences, viewing areas and wardens. Never touch or feed a seal, and report injured or entangled animals to local marine mammal rescue groups rather than handling them.