Grey Seal

The Grey Seal is one of the largest pinnipeds found in the North Atlantic, known for its distinctive elongated 'horse-like' head profile. It inhabits rocky coastlines, sandbanks, and islands, breeding in large colonies. Remarkable for its size dimorphism and deep diving capability, it is a keystone marine predator in coastal ecosystems.

North Atlantic coasts, including the United Kingdom, Ireland, Scandinavia, Baltic Sea, Iceland, and eastern Canada (Nova Scotia, Sable Island)

North Atlantic Ocean including the coasts of the United Kingdom, Ireland, Norway, Iceland, the Baltic Sea (Sweden, Finland, Estonia), and eastern Canada (Sable Island, Gulf of St. Lawrence) and the northeastern United States.

Altitude and depth

Dives typically range from 30-70m but can exceed 300m; spends most time in coastal shelf waters.

Seasonal movements

Breeding season occurs in autumn (UK/Atlantic populations, Sept-Dec) or late winter/spring (Baltic population, Feb-March); molting occurs annually in late winter/spring.

Rocky shores, sandy beaches, offshore islands, and sandbanks used for breeding and molting; open ocean waters for foraging.

Adaptations to its environment

Thick blubber layer for insulation in cold waters, streamlined body for efficient swimming, and specialized vascular system for thermoregulation and deep diving; can slow heart rate during dives (bradycardia).

Least Concern (LC) according to IUCN, as populations have recovered significantly since legal protections were introduced in the 20th century after historic overhunting.

Estimated population

Approximately 400,000-500,000 individuals globally, with populations generally increasing or stable, particularly in the UK and Baltic regions.

Historical hunting, bycatch in fishing gear, pollution (including PCBs), disease outbreaks (phocine distemper virus), and habitat disturbance from human activity.

Diseases and parasites

Susceptible to phocine distemper virus (PDV), various parasitic worms, and skin lesions; occasional outbreaks have caused significant mortality events.

Protected under various national laws (e.g., UK Conservation of Seals Act), EU Habitats Directive, and monitored through long-term population surveys; some culls are still permitted in certain regions to manage fishery conflicts.

Recommended actions

Continued monitoring of population health, reduction of bycatch through modified fishing gear, pollution control, and management of human-seal conflict in fishing areas.

Coat coloration varies widely from light grey to dark brown/black with distinctive blotches and spots; males tend to be darker with lighter patches, females lighter with dark spots.

Size

Males: 2.0-2.3m; Females: 1.6-2.0m in body length.

Weight

Males: 170-310 kg; Females: 100-190 kg.

Distinctive features

Distinguished from harbor seals by its larger size, longer straight/convex 'Roman nose' profile, and widely spaced nostrils that form a 'W' shape.

Differences between males and females

Significant sexual dimorphism: males are notably larger and heavier than females, with thicker necks, more pronounced 'Roman nose' profile, and darker coloring.

Generally solitary at sea but highly social during breeding and molting seasons, forming large colonies on beaches with hundreds to thousands of individuals; males establish dominance hierarchies to access females.

When it is active

Diurnal and nocturnal activity patterns, with foraging trips occurring at various times; hauls out on land during breeding, molting, and resting periods.

Diet

Carnivorous, feeding primarily on a wide variety of fish including cod, herring, sand eels, flatfish, and occasionally cephalopods and crustaceans.

How it feeds and hunts

Solitary hunter using echolocation-like whisker sensitivity (vibrissae) to detect prey movements in murky water; dives to seafloor to forage benthic and pelagic fish.

Communication

Vocalizations include growls, grunts, and roars especially during breeding season for territorial and mating displays; also uses body posturing and scent for communication.

Interactions with other species

Natural predators include killer whales and occasionally large sharks; competes with other seal species and seabirds for fish resources; interacts with human fisheries.

Role in its ecosystem

Acts as an important mid-to-upper trophic level predator in coastal marine ecosystems, helping regulate fish populations and serving as prey for apex marine predators.

Breeding occurs once yearly with a gestation period of about 11 months (including delayed implantation); females give birth to a single pup per season.

Raising the young

Females provide intensive maternal care, nursing pups with extremely fat-rich milk for about 3 weeks before weaning; pups are left to fend for themselves shortly after weaning.

Maturity and lifespan

Sexual maturity reached around 3-5 years for females and 4-6 years for males; lifespan averages 25-35 years in the wild, occasionally longer in captivity.

Classification

Mammalia > Carnivora > Phocidae > Halichoerus > Halichoerus grypus

Subspecies

Three recognized populations/subspecies-level groups are often described: Halichoerus grypus grypus (Baltic Sea), Halichoerus grypus macrorhynchus (Atlantic), and Halichoerus grypus atlantica (Western Atlantic/Canada), though taxonomic status is debated.

Scientific synonyms

Phoca grypus (original name given by Fabricius, 1791)

Recent studies

Recent studies have used satellite tagging to reveal long-distance foraging trips and diving behavior, as well as genetic research clarifying population connectivity across the North Atlantic.

Genome and DNA

Diploid chromosome number of 32; genomic studies have been used to assess population structure and genetic diversity across Atlantic and Baltic populations.

Compared with similar species

Often compared to the Harbor Seal (Phoca vitulina), which is smaller with a more rounded head and V-shaped nostrils, whereas the Grey Seal has a longer snout and parallel nostrils.

Grey seal pups are born with a white lanugo coat that is shed after a few weeks; some individuals can dive to depths exceeding 300 meters; grey seals can hold their breath for up to an hour.

Where and how to see it

Best observed at breeding colonies in autumn (UK, Ireland) or late winter (Baltic Sea); popular sites include the Farne Islands (England), Donna Nook (England), and Sable Island (Canada).

Risks to humans

Generally low risk to humans, though seals can bite if threatened or approached too closely; caution advised during breeding season when adults are more aggressive.

Human uses

Historically hunted for meat, oil, and pelts; today primarily valued for ecotourism and scientific research rather than commercial exploitation.

Myths and legends

In Celtic folklore, grey seals are associated with 'selkies,' mythical creatures that can transform from seals into humans.