Harbour Seal

The Harbour seal, also known as the Common seal, is the most widely distributed pinniped, found along temperate to Arctic coastlines of the North Atlantic and North Pacific. Recognisable by its rounded head, large dark eyes, and short, dog-like snout, it shows remarkable variation in coat colour, ranging from pale grey with dark spots to almost black with light rings.

Harbour seals are adaptable, opportunistic feeders, eating fish, squid, crustaceans, and molluscs, and can consume up to eight kilograms of food a day. Although they often live close to human settlements, they are naturally shy and spend much of their time in the water, usually foraging alone. They are most commonly seen hauled out on beaches, rocks, sandbars, or ice, where they rest, regulate body temperature, moult, or avoid predators. Despite being widespread and listed as Least Concern globally, harbour seals face local threats from fishing activities, pollution, and habitat disturbance, making them an important indicator species for the health of coastal ecosystems.

Diet and Behaviour

Harbour seals are adaptable, opportunistic predators with a diet that varies by season, location, and prey availability. They feed on a wide range of marine organisms, including fish, squid, crustaceans, and molluscs. Many of the fish species they consume are also targeted by commercial fisheries, which can lead to conflict. Harbour seals often take fish from nets and may become accidentally entangled. Adult seals typically consume approximately 4.5–8.2kg of food per day, adjusting intake based on energy needs and prey abundance.

These seals are generally shy and cautious, despite often living near human-populated coastlines. They spend much of their time in the water, where they are usually solitary while foraging. Their apparent sociability is mostly observed when they are hauled out on land, though even then adults tend to avoid physical contact with one another.

They haul out onto rocks, beaches, sandbars, islands, and ice (in Arctic regions) for resting, thermoregulation, moulting, and protection from predators. In areas where predators such as orcas are present, harbour seals may increase haul-out behaviour as a defensive response. While hauled out, adults maintain personal space, whereas younger seals may interact along the edges of the group but generally keep away from adults.

The Harbour seals remain close to water when hauled out, allowing for quick escape if threatened. Their behaviour reflects a balance between energy conservation, predator avoidance, and access to feeding areas, making them well adapted to a wide range of coastal environments.

Breeding Cycle

Harbour seals have a seasonal breeding cycle that varies by region and subspecies, largely influenced by climate and food availability.

Breeding begins with pupping, which occurs from early spring to early summer. Pregnant females seek out quiet, isolated haul-out sites such as upper bays and estuaries, coastal islands, beaches, sandbars, rocky ledges, or ice floes in Arctic regions. Females usually give birth to a single pup and are generally solitary or found in small, loosely spaced groups at this time.

Most pups are born with a grey, spotted coat similar to adult pelage, though some Arctic pups are born with a white lanugo coat that is shed within about two weeks. Pups can swim shortly after birth. Mothers nurse their pups for approximately 30 days, feeding them either on land or in the water.

After weaning, females enter oestrus roughly six weeks after giving birth (about two weeks after the pup is fully weaned). The mating season follows soon after. Both males and females engage in pre-mating behaviours, including rolling, bubble blowing, and mouthing one another’s necks. When mating begins, males actively pursue females by chasing, playful biting, and embracing, with copulation usually occurring in the water.

Male harbour seals are polygynous and promiscuous, mating with multiple females during the breeding season. After mating, females experience delayed implantation, a reproductive strategy that allows the embryo to pause development so that birth the following year occurs at an optimal time. Sexual maturity is reached between 2–6 years in females and 3–7 years in males, depending on body condition and regional food supply.

Harbour Seal FAQs

Scientific name	Phoca Vitulina
Length	1.4 - 1.9m (4.6 - 6.2ft)
Weight	55 - 170kg
Population	350,000 - 500,000 individuals
Species Conservation Status	Least Concern

Quick Harbour Seal Facts

Diet and Behaviour

Breeding Cycle

Harbour Seal FAQs

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