[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.

[8][11][12] It is distinguished from the smaller harbor seal by its straight head profile, nostrils set well apart, and fewer spots on its body.

Notably large colonies are at Blakeney Point in Norfolk, Donna Nook in Lincolnshire, the Farne Islands off the Northumberland Coast (about 6,000 animals), Orkney and North Rona.

[18] In the western North Atlantic, the grey seal is typically found in large numbers in the coastal waters of the Maritime Provinces of Canada and south to Nantucket in the United States.

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.

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.

[29] 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.

[30][31][32] 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.

[37] 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.

[43] Male grey seals engage in aggressive sexual behaviour, which to can lead to severe injuries and even death for the female.

[45] After near extirpation from hunting grey seals for oil, meat, and skins in the United States, sightings began to increase in the late 1980s.

[48] A count of 15,756 grey seals in southeastern Massachusetts coastal waters was made in 2011 by the National Marine Fisheries Service.

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.

[50] Grey seals have proved amenable to life in captivity[citation needed] and are commonly found in zoo animals around their native range, particularly in Europe.