Phoca vitulina subs. vitulina Linnaeus, 1758 (juvenile)
Phoca vitulina subs. vitulina Linnaeus, 1758 (juvenile)
Common names: Harbor seal, Common seal [En], Phoque commun, Phoque veau-marin [Fr], Gewone zeehond [Nl], Seehund [De], Foca comune [It], Foca común, Foca de puerto, Foca moteada [Es]
IUCN Status : LC (Least Concern)
Berck-sur-Mer, PAS-DE-CALAIS ● France
Description: Adult male Harbour Seals are up to 1.6 m long and weigh an average of 75 kg, whereas females are 1.5 m long and 67 kg. At birth, pups are 81 cm long and weigh 8.7 kg. Longevity is about 35 years with females living longer than males.
Five subspecies are recognized:
• P. v. concolor – Western Atlantic Harbor Seal – western Atlantic from the mid-Atlantic United States to the Canadian Arctic and east to Greenland and Iceland;
• P. v. mellonae – the Ungava Seal or Seal Lake Seal – a few lakes and rivers in northern Quebec, Canada, that drain into Hudson and James Bays;
• P. v. richardii – the Eastern Pacific Harbor Seal – eastern Pacific from central Baja California, Mexico to the end of the Alaskan Peninsula and possibly to the eastern Aleutian Islands;
• P. v. stejnegeri – the Kuril Seal or Western Pacific Harbor Seal – from either the end of the Alaskan Peninsula or the eastern Aleutians to the Commander Islands, Kamchatka, and through the Kuril Islands to Hokkaido;
• P. v. vitulina – the Eastern Atlantic Harbor Seal – eastern Atlantic from Brittany to the Barents Sea in northwestern Russia and north to Svalbard, with occasional sightings as far south as northern Portugal.
Biology: Although Harbour Seals are gregarious at haul-out sites, they usually do not lie in contact with each other. They will haul out on rocks, sand and shingle beaches, sand bars, mud flats, vegetation, and a variety of man-made structures. They usually lie close to the water to permit a rapid escape from threats.
They are usually extremely wary and shy on land. However, habituation to human activities in their vicinity can occur. Although generally considered a non-migratory species with a high degree of site fidelity to a haul out, long-distance dispersal of juveniles, emigration and establishment of new haul out sites do occur. There is also evidence of seasonal changes in at-sea distribution and home range size by age class and sex.
Male Harbour Seals become sexually mature when 4-6 years old. Female Harbour Seals usually become sexually mature when 3-5 years old. Gestation lasts 10.5-11 months, including a 2+ month delayed implantation. Pupping occurs in June and July throughout most of the Eastern Atlantic Harbour Seal’s range. The mating system is promiscuous, or weakly polygynous, with males defending underwater calling sites. Mating usually takes place in the water, with females coming into oestrus about a month after giving birth. Moult follows the pupping and mating season.
Female Harbour Seals give birth to a single precocial pup. Most pups shed their silvery gray lanugo coat in the uterus before birth and are born with a juvenile pelage. Pups usually enter the water soon after birth. Pups are suckled for an average of 26 days. Unlike Grey Seals, Harbour Seal females need to feed during the lactation period to produce adequate milk for their rapidly growing pup. As a result they undertake regular feeding trips to sea.
Harbour Seals are generalist feeders that take a wide variety of fish, cephalopods, and crustaceans obtained from surface, mid-water, and benthic habitats. Generally, a few species dominate the diet at any one location and time of year. In the Eastern Atlantic, Harbour Seals eat a variety of fish species such as Sandeel, Sprat, Sole, Dab, Whiting, Atlantic Cod and flatfishes as well as Octopus.
Known predators include Killer Whales, Great White and Greenland Sharks, Gulls, and Eagles.
Habitat: Eastern Atlantic Harbour Seals are mainly found in the coastal waters of the continental shelf and slope, and are also commonly found in bays, rivers, estuaries, and intertidal areas. They are primarily a coastal species with dive depths generally less than 100 m, but foraging in deeper waters occurs in some areas.
Distribution: Eastern Atlantic Harbor Seals occur along the coasts of Svalbard, Norway, Iceland, Denmark, Sweden, Germany, Netherlands, France, Ireland, and the United Kingdom.
Threats: Harbor Seals are distributed very widely and their total population size is estimated at about 600,000. Trend in abundance is unknown for four of the subspecies; the Eastern Pacific Harbor Seal is known to be increasing. While in many areas Harbor Seals share the coastal zone with increasing human populations and suffer some impacts as a result, current threats appear to be tolerable and/or manageable. However, the subspecies Phoca vitulina mellonae, the Ungava Seal, is listed separately as Endangered.
Historical population reductions of Eastern Atlantic Harbour Seals in the Baltic Sea, Wadden Sea, and France were due to hunting, and in the Baltic Sea also due to the effects of contaminants. Along the Belgian coast, Harbour Seals were frequently sighted until the 1950s, but thereafter there were no colonies due to high levels of disturbance.
Mass die-offs from viral outbreaks have claimed thousands of Harbour Seals on both sides of the Atlantic, but most notably in Europe caused by phocine distemper virus. Because Harbour Seals haul out on nearshore and coastal mainland sites, they are exposed to terrestrial wild carnivores, pets and feral animals, and waste from human populations, which create an increased risk of exposure to communicable diseases.
Because many Harbour Seals live and feed in close proximity to large populations of humans they are exposed to, and can accumulate, high levels of industrial and agricultural pollutants (e.g., organochlorines, PCBs, dioxins) that negatively affect reproduction and cause immunosuppression. Both chronic oil spills and discharges and episodic large scale spills can cause direct mortality and could have long term impacts on Harbour Seal health and their environment.
Noise and other disturbance from offshore oil and gas and the development of offshore renewables, such as wind farms, may also affect the foraging behavior and physical condition of Harbour Seals.
Overfishing and environmental variability (including global climate change) may also impact Harbour Seal prey populations.
Conservation actions: Harbour seals at Svalbard are protected under the Norwegian National Red List. Hunting of Harbour Seals in the Baltic Sea was prohibited in 1970 and management of this species in the Baltic Sea and Southern Scandinavian waters is the responsibility of HELCOM. Denmark and Sweden have established Harbour Seal sanctuaries. Neighbouring states of the Wadden Sea have signed a trilateral agreement for the management of Harbour Seals. Since 1994, Harbour Seals have been considered vulnerable on the French national Red List. In the UK, Harbour Seals are protected under the Conservation of Seals Act and the Marine Scotland Act.
Bowen D., 2016. Phoca vitulina ssp. vitulina, The IUCN Red List of Threatened Species.
Lowry L., 2016./b> Phoca vitulina, The IUCN Red List of Threatened Species.