The gray seal (Halichoerus grypus) is a large, common species of true seal. It is sometimes called the Atlantic seal or the horsehead seal, due to the distinct, arched nose of the adult male. The species is widespread across the cool, temperate, and subarctic regions of the North Atlantic Ocean. Its distribution is confined exclusively to these northern waters, establishing it as a defining species of the Atlantic ecosystem.
Global Range and Distribution
The geographical range of the gray seal is separated into two major areas, spanning the eastern and western sides of the North Atlantic basin. They inhabit coastal waters and shelves where cooler temperatures and abundant food sources are prevalent. This species does not migrate between the two sides of the ocean, leading to distinct genetic and behavioral differences in the populations.
The Western Atlantic population is found along the coastlines of North America, while the Eastern Atlantic population occupies European shores. These populations are considered reproductively isolated stocks, meaning there is little to no intermixing. This geographic isolation has resulted in unique management and study approaches for the seals on each side of the ocean.
Distinct Regional Populations
The gray seal population is formally divided into three major, geographically separate stocks.
The Western Atlantic population is centered in the Canadian Maritime Provinces. This group ranges from northern Labrador down to the waters off New England, with individuals occasionally sighted as far south as Virginia. The largest breeding colonies are found on Sable Island and in the Gulf of St. Lawrence.
The Eastern Atlantic stock is the largest of the three, with the vast majority of its members concentrated around the British Isles. This population extends from Iceland and Norway, southward along the European continent to France and eastward to the White Sea in northwestern Russia. The United Kingdom alone hosts a significant percentage of the global gray seal population, making it a major hub for the species.
A third, highly isolated stock is located in the Baltic Sea, a brackish body of water nearly cut off from the main Atlantic Ocean. This population is genetically and geographically distinct from the other two Atlantic groups. Historically reduced by hunting and pollution, this Baltic Sea group adapted to a more enclosed marine environment.
Preferred Coastal and Aquatic Habitats
Gray seals utilize a variety of habitats, dividing their time between foraging in coastal waters and hauling out on land for resting, molting, and reproduction. They are found in cold, temperate to subarctic coastal areas. When at sea, they primarily feed in coastal waters, often taking prey from the seabed at depths up to 230 feet.
The land features they select for hauling out are remote and provide safety from predators and human disturbance. These features include isolated islands, large offshore rock outcroppings, and sandy beaches. In parts of their range, such as the Gulf of St. Lawrence, they also utilize land-fast ice or ice floes for pupping. These haul-out sites function as rookeries, where females gather to give birth and nurse their pups before they are weaned.