Harbour Seal

The Harbour Seal is one of the most widespread pinniped species, found along temperate and Arctic coastlines throughout the Northern Hemisphere. It is a true seal (earless) known for its adaptability to diverse coastal habitats and its distinctive spotted coat pattern. This species is notable for its curious, dog-like face and its ability to haul out on rocks, sandbars, and ice.

Coastal waters of the Northern Hemisphere including North America (both Atlantic and Pacific coasts), Northern Europe, and parts of Asia (Japan, Korea)

Found along coasts of the North Atlantic and North Pacific, including Canada, USA, Greenland, Iceland, UK, Scandinavia, Netherlands, Germany, Russia, Japan, and Korea; also present in a unique freshwater population in Quebec, Canada

Altitude and depth

Typically dives to 20-100m but capable of dives exceeding 400m; spends significant time at surface and on land/ice haul-out sites

Seasonal movements

Generally non-migratory but may show local seasonal movements tied to breeding, molting, and prey availability; pupping season varies by region from February to July

Coastal and estuarine environments including rocky shores, sandbars, mudflats, and sea ice; also found in bays, harbors, and occasionally freshwater lakes and rivers connected to the sea

Adaptations to its environment

Streamlined body and strong flippers for efficient swimming; thick blubber layer for insulation in cold waters; ability to slow heart rate during dives (bradycardia) for extended underwater foraging; vibrissae (whiskers) highly sensitive for detecting prey movement in murky water

Least Concern (LC) according to IUCN, as the global population is large and stable overall, though some regional populations face localized declines due to disease outbreaks and human disturbance

Estimated population

Global population estimated at 350,000-500,000 individuals, with overall stable trend though some subpopulations experiencing fluctuations

Habitat disturbance from human activity, pollution and contaminants, entanglement in fishing gear, disease outbreaks (phocine distemper virus), and historical hunting pressures in some regions

Diseases and parasites

Susceptible to phocine distemper virus (has caused mass die-offs), influenza strains, and various internal/external parasites including lungworms and seal lice

Protected under Marine Mammal Protection Act in the US, Habitats Directive in EU, and various national wildlife laws; monitored through population surveys and health assessments; some marine protected areas include key haul-out sites

Recommended actions

Continue monitoring for disease outbreaks, reduce bycatch in fishing operations, protect critical haul-out and pupping habitats from disturbance, and address pollution in coastal waters

Coat coloration is highly variable, ranging from light gray to dark brown/black, typically covered in dark spots or rings; body is rounded with a small rounded head and large dark eyes giving a dog-like appearance

Size

Body length typically 1.2-2.0 meters, with males slightly larger on average than females

Weight

Adults typically weigh 55-170 kg, with males averaging heavier than females; weight varies significantly by region and season

Distinctive features

Distinguished from other seals by V-shaped nostrils, lack of external ears, spotted coat pattern, and relatively small size compared to gray seals; shorter snout than harp or gray seals

Differences between males and females

Minimal sexual dimorphism; males are slightly larger and heavier than females but coloration and general appearance are similar between sexes

Generally solitary or found in small loose groups, though they may haul out in larger aggregations of dozens to hundreds of individuals on favored sites; not strongly hierarchical

When it is active

Cathemeral (active both day and night), with activity patterns often influenced by tidal cycles which dictate haul-out availability

Diet

Carnivorous, feeding primarily on fish such as herring, cod, flatfish, and sand eels, as well as squid and crustaceans depending on regional availability

How it feeds and hunts

Solitary hunters using stealth and speed to capture prey underwater; rely heavily on vibrissae to detect prey in low-visibility conditions and can perform deep dives to access benthic prey

Communication

Vocalizations include grunts, growls, and roars particularly during breeding season; underwater vocalizations used for mate attraction; body posturing and physical contact also used in social interactions

Interactions with other species

Predators include orcas, sharks (great white, sleeper sharks), and occasionally polar bears in Arctic regions; competes with other pinnipeds for haul-out sites and food resources; sometimes preyed upon by large birds of prey when pups are vulnerable

Role in its ecosystem

Plays a role as a mid-level marine predator, helping regulate fish populations and serving as prey for larger marine predators, thus contributing to coastal food web dynamics

Breeding season varies by region (roughly May-September); gestation lasts about 9-11 months (including delayed implantation); females give birth to a single pup that can swim within hours of birth

Raising the young

Pups are precocial and can swim almost immediately after birth; mothers nurse pups for approximately 4-6 weeks with rich milk before weaning; there is no paternal care, and males do not participate in raising young

Maturity and lifespan

Sexual maturity reached at 3-7 years; lifespan averages 20-30 years in the wild, with some individuals living up to 35 years in captivity

Classification

Class Mammalia > Order Carnivora > Family Phocidae > Genus Phoca > Species Phoca vitulina

Subspecies

Five recognized subspecies: P. v. vitulina (Eastern Atlantic), P. v. concolor (Western Atlantic), P. v. richardii (Eastern Pacific), P. v. stejnegeri (Western Pacific), P. v. mellonae (freshwater population in Lac des Loups Marins, Quebec)

Scientific synonyms

Phoca variegata, Callocephalus vitulinus, historically also referred to as Common Seal

Recent studies

Recent research has focused on the impacts of climate change on prey availability, tracking movement patterns via satellite tags, and studying disease transmission dynamics following distemper outbreaks

Genome and DNA

Diploid chromosome number is 32; genetic studies have been used to distinguish regional subspecies and track population structure and connectivity

Compared with similar species

Similar in appearance to the spotted seal (Phoca largha) but harbour seals have a more rounded head and different geographic range; smaller and less aggressive than gray seals (Halichoerus grypus)

Harbour seals can sleep underwater, surfacing periodically to breathe without fully waking; they have excellent underwater vision adapted for low-light conditions; some populations exhibit unique behaviors like resting vertically in water ('bottling')

Where and how to see it

Best observed during low tide when seals haul out on rocks or sandbars; coastal areas of Scotland, the Wadden Sea, and New England are popular viewing locations, especially during pupping season in late spring/summer

Risks to humans

Generally low risk to humans, though seals can bite if approached too closely or harassed; can carry zoonotic diseases in rare cases, so direct contact should be avoided

Human uses

Historically hunted for meat, oil, and pelts by indigenous and coastal communities; today primarily valued for ecotourism and scientific research rather than commercial exploitation

Myths and legends

In Celtic and Scottish folklore, seals are associated with 'selkies'—mythical beings that can transform from seals into humans by shedding their skin