Phoca vitulina

This species is gregarious; on land it forms groups to breed, rest and moult that are generally small but may number up to 1,000 individuals (5). Common seals feed mainly on a variety of fish, but squids, whelks, crabs and mussels are also taken. Juveniles feed on shrimps before progressing to the adult diet (2). When feeding, common seals travel up to 50 kilometres from haul-out sites to feed and may stay out at sea for days. They can dive for up to 10 minutes, and reach depths of 50 metres or more (3). With regards to breeding, there is apparently no social organisation, but females often give birth in small groups (7). Females give birth to a single pup at the end of June to early July (8). The pups weigh 11 to 12 kilograms at birth and are able to swim and crawl almost immediately (2). Pups are nursed for about four weeks, after which they may disperse over long distances (5). Around the time that the pup is weaned, females become receptive and copulation occurs. Males frequently engage in underwater displays and fights around this time and can lose up to 25 percent of their body weight (5).

Harbor Seals live near coastlines and eat a highly varied seafood diet, depending on what is available. They can dive as deep as 450 m and stay under for almost half an hour, but six-minute dives to depths of 30-100 m are more usual. Females usually have one pup a year, and two weeks after the pup is born, mate again. The fertilized egg stays dormant in the uterus for up to three months before it implants in the uterine wall and begins to grow. This is called delayed implantation. Total gestation, including the period of delay, lasts 8-9 months. Instead of being born with the white coat typical of most seals in the family Phocidae, the pups often molt before birth, shedding the very soft white or pale gray coat called a lanugo while they are still in the uterus. Like dogs, Harbor Seals can suffer from heartworm. The disease has been found in North American and European populations.

Links:
Mammal Species of the World

Harbour seals are good swimmers. The pinipeds serve as rudder. The body and back pinnipeds cause propulsion. The seal is highly adapted to speed with its torpedo-like body and pinna. Observations made from ships revealed that they generally swim just 10 m beneath the water surface and that only rarely will they hunt under –20 m.  Young harbour seals are born on tide-sandbanks between the end of June and mid July, and are required, almost immediately (during high-tide) to be able to swim. 

 In general, harbour seals feed on benthic fish (such as flounder, sole, cod and whiting), but they must largely be quite opportunistic in regard to what they eat. They may also feed on mussels, crabs and cephalopods.

Phoca vitulina, the Harbour or Common seal, is a marine mammal frequently seen around the UK coastline.Harbour seals are vulnerable to viral distemper which is causing mass mortalities, losses were particularly high in 1988 and 2002.Since these seals spend much of their time in water, estimating population numbers is not easy but worryingly, numbers are declining progressively.

Also known as the harbour seal, the common seal is the smaller of the two breeding seals in Great Britain (6). When hauled out it often adopts a characteristic 'head-up, tail-up' posture. The colour is variable, ranging from black-grey to sandy brown with many small spots. The top of the small head is round and the nostrils form a 'V' (2). Males are often darker in colour than females and have a heavier appearance. The white natal coat of the young is shed inside the uterus; pups are therefore born with their first adult coat (2).

With the vast coastline of the UK and Europe monitoring seal populations is challenging. Members of the public often participate surveys and along your local coastline you can play an important role in alerting authorities to the occurrence of sickened animals during episodes of viral distemper.Further information about seals and their biology can be found at the Sea Mammal Research Unit.

Harbour seals are usually sexually mature after the first five years of life and can live up to 35 years of age.In UK-waters, harbour seals can sometimes be found alongside the larger grey seal (Halichoerus grypus). Both species are vulnerable to viral distemper caused by PDV (Phocine Distemper Virus) but mortalities in the grey seal are not as pronounced.

 Common seals have a rounded head with eyes equidistant between the nose and the ears. The nostril slits form a characteristic 'v' shape when viewed from the front. Adult common seals grow up to 1.2 to 2 metres long, and weigh around 65-140 kg. Males are slightly bigger than females. The coat is grey to brownish-grey with a uniform pattern of small darker spots, although the pattern varies geographically. Individuals may live for 20-30 years (SMRU, 2004).May be confused with the grey seal (Halichoerus grypus) that has a much longer muzzle and their nostril slits are nearly parallel.  

Seals are highly adapted to live in water. Their limbs are modified into flippers and they have streamlined bodies. Phoca vitulina can dive to 450 m and remain submerged for up to 30 minutes. The common seal is a strong swimmer and can be seen leaping completely out of the water (porpoising) (Nowak, 2003). Only the head is usually seen when the seal is in water. As well as being fur-coated they have a thick layer of subcutaneous fat or blubber. This keeps them warm and enhances streamlining (SMRU, 2004). Seals are warm-blooded air-breathing mammals but spend a considerable amount of time below the water surface. Common seals give birth to pups in June and July and moult in August. The main threat to seals in the UK and Ireland is organochlorine compounds that may interfere with reproduction (SMRU, 2004).

 The Common or harbour seal has been reported as non-migratory and littoral in distribution and as exhibiting a diurnal haul-out pattern (Evans & Raga, 2001). Common seals in Europe belong to a distinct sub-species. Britain holds around 40% of the world population of the European sub-species (Duck & Thompson, 2003).

 The Conservation of Seals Act, 1970, provides a closed season for the Common seal during its pupping season. During this time, it is illegal to kill or take seals without a licence. There is also provision for giving complete protection to seals at al times, if neccesary. During the close season, a license is required to handle seals unless they are sick or injured (SMRU, 2004). The Baltic and Wadden Sea populations are listed under the Bonn Convention (Appendix II).

Phoca vitulina is the most widely distributed pinniped. This species is found in temperate, subarctic, and arctic coastal areas on both sides of the North Atlantic and North Pacific oceans. Five separate subspecies have been identified, each common to a specific coastal region.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); atlantic ocean (Native ); pacific ocean (Native )

Other Geographic Terms: holarctic

North America

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Temperate and subarctic regions of the Northern Hemisphere. In the western North Atlantic, breeds at least from Cape Dorset on southwestern Baffin Island to Massachusetts; occurs along west coast of Greenland as far north as Disko Island and Avanersuaq, along the east coast to Ittoqqortormiit (Teilman and Dietz 1994); small numbers occur, mostly in river mouths, in parts of Hudson Strait, Ungava Bay, and Hudson Bay; small local populations inhabit some rivers and lakes of western Hudson Bay, moving as far as 240 km inland; small population occurs in the Lacs des Loups Marins (Seal Lakes) at the headwaters of the Nastapoka River in northern Quebec; large population breeds on Sable Island, 125 km off Nova Scotia; extirpated from Lake Champlain and Lake Ontario; sometimes ranges as far north as Ellesmere Island and as far south as Florida (Reeves et al. 1992, which see for distribution in eastern North Atlantic. In the eastern Pacific, breeds from Bahia San Quintin, Baja California, to Aleutian Islands, Pribilof Islands, and Nome, Alaska; in the western Pacific, Commander Islands south to Hokkaido, Japan (Reeves et al. 1992). In eastern North Atlantic, ranges from Murmansk to the outer Baltic and northern France, United Kingdom south to east Anglia, southern Ireland, Faroes, Spitsbergen, and Iceland (McLaren, in Macdonald 1985).

Harbour seals are mainly founded focused along the north-western coastline of Scotland.Along the English coastline there are large colonies in the Wash and sub-colonies on northern parts of the Norfolk.Across the North Sea there are likely to be some 30,000 animals.

The common seal is found from the subtropics to the Arctic around coasts of the North Atlantic and the North Pacific (6). In Europe they occur off Icelandic, Danish, German, Dutch and Icelandic coasts as well as around the UK. The UK supports 45 percent of the European population (five percent of the world population); main centres of population occur in the Moray Firth, The Wash and the Tay Estuary, and the species is fairly widespread around west Scotland, the Northern Isles and the Hebrides (6).

Harbor seals can be up to 6 feet long and weigh up to 375 pounds, males characteristically being slightly larger than females. The rounded, fusiform body is covered by a coat made of thick, short hairs that range from nearly white with dark spots to black or dark brown with white rings. The dorsal surface is usually more densely covered with spots or rings than the ventral surface.

The limbs of the harbor seal have been modified into flippers. The foreflippers (pectoral flippers) are composed of 5 digits of similar length and webbed together. Claws on the foreflippers are used for scratching, grooming, and defense. The hind flippers also have 5 digits; however, the first and fifth digits are long and stout, while the middle digits are shorter and thinner. The hind flippers propel the seal forward by moving side to side. On land, the harbor seal moves by undulating in a caterpillar-like motion.

Range mass: 50 to 170 kg.

Range length: 2 (high) m.

Sexual Dimorphism: male larger

Average basal metabolic rate: 73.29 W.

Length: 170 cm

Weight: 136000 grams

Sexual Dimorphism: Males are slightly larger than females.

Length:
Average: 1.8 m males; 1.5 m females

Weight:
Average: 130 kg males; 105 kg females

Harbour seals can reach up to 1.6 m in length and weigh about 120 kilos. Their colour varies from grey to brown with black marks. A characteristic feature is their V-shaped nostrils.

Distinguishing Characteristics: small in size in relation to seals, dog-like face, v-shaped nostrils, colour varies from white to tan to dark brown to red (molttled):

Harbor seals bask and sleep on coastal islands, ledges, and beaches and sandbars that are uncovered at low tide. They stay close enough to water to facilitate feeding and mating.

Habitat Regions: temperate ; saltwater or marine

Aquatic Biomes: coastal

nearshore waters of the Atlantic Ocean and adjoining seas above about 30 degrees latitude

temperate to polar

Depth range based on 9881 specimens in 1 taxon.
Water temperature and chemistry ranges based on 896 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 0.297 - 21.498
  Nitrate (umol/L): 0.240 - 12.040
  Salinity (PPS): 30.381 - 35.656
  Oxygen (ml/l): 5.180 - 8.103
  Phosphate (umol/l): 0.205 - 1.202
  Silicate (umol/l): 0.987 - 22.664

Graphical representation

Temperature range (°C): 0.297 - 21.498

Nitrate (umol/L): 0.240 - 12.040

Salinity (PPS): 30.381 - 35.656

Oxygen (ml/l): 5.180 - 8.103

Phosphate (umol/l): 0.205 - 1.202

Silicate (umol/l): 0.987 - 22.664
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Marine

Comments: Coastal waters to about 10 miles offshore, bays, harbors, coastal rivers, lakes. Most common in protected areas such as bays or inlets, much less numerous along simple open coastlines. Some frequently occur in freshwater bodies connected to the ocean. Resident year-round in freshwater in Lacs des Loups Marins (Quebec; Smith, 1996 COSEWIC report) and possibly in Lake Iliama (Alaska). Rests on isolated mudbanks, rocky or sandy shores, intertidal ledges, reefs, islands; sometimes piers and log rafts; also on ice in some areas (Scheffer 1958, Boulva and McLaren 1979, Johnson and Jeffries 1977, Burns and Gol'tsev 1984, Hoover 1988).

Pups are born on shore, often in an intertidal area; secluded sites and areas beyond strong wave action.

 The common seal lives mainly along shorelines and in estuaries. It is commonly seen resting on sandbanks, easily accessible beaches, reefs and protected tidal rocks.

Common seals seem to prefer sheltered waters. They haul out on a range of habitats such as rocky shores, sand and gravel beaches, mudflats and sand bars. Preferred haul out sites are protected against land predators and strong winds or waves, are close to food sources and enable direct access to deep water (5).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

In some areas, makes seasonal migrations of up to at least several hundred kilometers. Many seals that summer in Bay of Fundy and Maine apparently migrate southward to winter in southern New England (Rosenfeld et al. 1988). In southern California, adults remain close to the Channel Islands year-round (Reeves et al. 1992).

The diet varies with the season and region. Their food consists of crustaceans, mollusks, squid, and a variety of fish. Harbor seals do not chew their food; they either tear it into chunks or swallow it whole. Their molars allow them to crush hard objects like shells and crustaceans. Adults consume around 4.5 to 8.2 kg of food per day, which is 5-6% of their body weight.

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore )

Comments: Newly weaned pups eat mainly bottom-dwelling crustaceans. Older individuals feed opportunistically on various fishes and some cephalopods and crustaceans. In southern California, most dives were 17-87 m (sometimes up to several hundred meters).

Harbor seals are eaten by great white sharks and killer whales.

Known Predators:

• great white sharks (Carcharodon carcharias)
• killer whales (Orcinus orca)

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: Hundreds of haulouts worldwide.

10,000 to >1,000,000 individuals

Comments: Total population probably is at least 500,000. Population in eastern Canada south of Labrador was about 13,000 (and increasing) in the mid-1980s. In 1986, nearly 13,000 were counted at haul-out sites in Maine. Several thousand occur in winter in coastal southern New England. Total population in the North Pacific was estimated at more than 300,000 in 1979, with at least two-thirds of these in Alaska. Post-pupping population in British Columbia was 75,000-88,000 in the late 1980s. California population was estimated at 34,500 in the mid-1990s (NMFS, Federal Gister, 15 March 1996). See Reeves et al. (1992) for information on

Dimethyl Sulfide or DMS is present throughout the ocean(1). It’s an important odor component of many fish and shellfish, including clams, mussels, oysters, scallops, crabs and shrimp(2-9). Where does it come from? Usually from the marine plants they feed on.

Many species of plants and algae produce DMS, but not all species produce significant amounts of it. Nearly all of these are marine, and they tend to be in closely related groups with other DMS-producers, including Chlorophyte (green) seaweeds, the Dinophyceae in the dinoflagellates, and some members of the Chrysophyceae and the Bacillariophyceae (two classes of diatoms). Other large groups, like cyanobacteria and freshwater algae, tend not to produce DMS. (10,11)

Why do these groups produce DMS? In algae, most researchers believe a related chemical, DMSP, is used by the algae for osmoregulation- by ensuring the ion concentration inside their cells stays fairly close to the salinity in the seawater outside, they prevent osmotic shock. Otherwise, after a sudden exposure to fresh water (rain at the sea surface, for instance) cells could swell up and explode. In vascular plants, like marsh grasses and sugar cane, it’s not clear what DMS is used for. (12,13)

Freshly harvested shellfish can smell like DMS because DMSP has accumulated in their tissue from the algae in their diet. Some animals, including giant Tridacna clams and the intertidal flatworm Convoluta roscoffensis, harbor symbiotic algae in their tissues, which produce DMSP; this may not be important to their symbioses, but for Tridacna, the high DMS levels can be a problem for marketing the clams to human consumers. After death, DMSP begins to break down into DMS. A little DMS creates a pleasant flavor, but high concentrations offend the human palate.(2,14)

Not all grazers retain DMS in their tissues, though. At sea, DMS is released when zooplankton feed on algae. It’s been shown in the marine copepods Labidocera aestiva and Centropages hamatus feeding on the dinoflagellate Gymnodinium nelson that nearly all the DMS in the consumed algae is quickly released during feeding and digestion.(15) This has a disadvantage for the grazing zooplankton. Marine predators, like procellariiform seabirds, harbor seals, penguins, whale sharks, cod, and coral reef fishes like brown chromis, Creole wrasse and boga, can use the smell of DMS to locate zooplankton to feed on. (8,16,17)

It’s not easy to measure how much DMS is released from the Ocean into the air every year. Recent estimates suggest 13-37 Teragrams, or 1.3-3.7 billion kilograms. This accounts for about half the natural transport of Sulfur into the atmosphere, is the conveyor belt by which Sulfur cycles from the ocean back to land. In the atmosphere, DMS is oxidized into several compounds that serve as Cloud Condensation Nuclei (CCN). The presence of CCN in the air determines when and where clouds form, which affects not only the Water cycle, but the reflection of sunlight away from the Earth. This is why climate scientists believe DMS plays an important role in regulating the Earth’s climate. (12,18)

Mainly solitary in water, forms usually small groups when ashore or out of water on exposed rocks (sometimes up to several hundred). Mean maximum distance between haulout sites used by adults in Alaska was 14.7 kilometers; at-sea foraging area size averaged 267 square kilometers for adults and 385 square kilometers for subadults (Small and ver Hoef 2001).

Common causes of mortality include abandonment or orphaning of pups and predation by sharks, killer whales, and sometimes other mammals. Also, outbreaks of disease (influenza, distemper) sometimes kill hundreds or thousands of individuals in a local or regional population.

Communication Channels: acoustic

Perception Channels: visual ; acoustic

Using special tagging devices it is possible to record the movements of animals.Adults are capable of dispersing widely throughout the North Sea but more usually stay 5-20km around their haul-out sites, diving and locally foraging for food.British and Danish populations often intermingle and in so doing sometimes spread viral distemper.

Comments: Activity pattern governed by tides and weather. Usually rests on shore or on rocks exposed during low tide.

Average lifespan
Status: wild: 34.0 years.

Average lifespan
Status: wild: 40.0 years.

Average lifespan
Sex: male
Status: wild: 26.0 years.

Average lifespan
Sex: female
Status: wild: 32.0 years.

Maximum longevity: 47.6 years (captivity) Observations: In the wild, these animals are believed to live up to 40 years (Bernhard Grzimek 1990). One wild born specimen was about 47.6 years of age when it died in captivity (Richard Weigl 2005).

Pre-mating behavior is exhibited by both males and females, such as rolling, bubble-blowing, and mouthing each other's necks. This behavior ends once mating begins. Males initiate behavior by chasing, playfully biting, and embracing females. Females respond, and the act of copulation usually takes place in the water. One male may mate with multiple females. Harbor seals return to the same breeding grounds every year.

Mating System: polygynous

It is believed that males become sexually mature once a weight of around 75 kg is achieved; females mature at about 50 kg. This occurs between 3 and 7 years of age for males and at 2 to 6 years for females. While the mating season varies between the different subspecies, it generally occurs from late spring through fall. About 6 weeks after they give birth to their previous year's pups, the females come into estrus. The gestation period lasts between 9 and 11 months, and usually only 1 pup is born each year.

Breeding season: While the mating season varies between the different subspecies, it generally occurs from late spring through fall.

Average number of offspring: 1.

Range gestation period: 9 to 11 months.

Range age at sexual or reproductive maturity (female): 2 to 6 years.

Range age at sexual or reproductive maturity (male): 3 to 7 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous ; delayed implantation

Average birth mass: 11000 g.

Average number of offspring: 1.

Local birth season exhibits high degree of geographic variation, lasts 1-2 months within a particular area. Births occur mainly in May-June in Gulf of Alaska, Nova Scotia, and Newfoundland; June-July farther north in western Atlantic; February-March in Baja California. Lactation lasts 2-6 weeks (average about 3-4 weeks), followed within a few days by ovulation and mating, then blastocyst implantaion 1.5-3 months later. Females continue to forage during lactation period. Young weaned in 2-6 weeks (usually about 4 weeks). Females sexually mature in 3-6 years, males in 3-7 years. Few live beyond 25 years.

The U.S. Marine Mammal Protection Act of 1972 made it illegal to hunt or harass any marine mammal in U.S. waters. In Canada, Norway, and the United Kingdom, it is legal to shoot harbor seals to protect fisheries or fish farms. Many fish species eaten by harbor seals are also commercially fished, and the seals often become entangled and drown in fishing nets and gear.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Worldwide distribution; high abundance; precipitous decline in some areas, increases in other areas; suspected threats include food shortages resulting from local fisheries management practices, incidental and intentional take, disease, and entanglement in marine debris.

Classified as Least Concern (LC) on the IUCN Red List (1). Protected in Britain under the Conservation of Seals Act 1970 (closed season from 1 September until 31st December) (3) and schedule 3 of the Conservation Regulations (1994) (4). Listed as a protected species under Annex II and Annex V of the European Community's Habitats Directive. The eastern Atlantic population is listed under Appendix III of the Bern Convention. Subpopulations in the Baltic and Wadden Seas are listed under Appendix II of the Bonn Convention (5).

Degree of Threat: A : Very threatened throughout its range communities directly exploited or their composition and structure irreversibly threatened by man-made forces, including exotic species

Comments: Pacific Ocean: Recent precipitous declines in the numbers of harbor seals observed at some traditional haulout areas indicate that a fairly high level of threat exists to the long-term viability of these populations. These declines have been most recently documented in the Bering Sea region, where comparable declines have also been documented for both fur seals and Steller's sea lions (Pitcher 1990, Fowler 1982, 1985, York and Kozloff 1987, Braham et al. 1980, Merrick et al. 1987, Calkins and Goodwin 1988). The causes for these declines are not fully known, but food shortages, disease, and entanglement in marine debris are primary factors currently being investigated (Pitcher 1990). Large numbers die from entanglement in gill nets in some areas (annually perhaps 5% of the population in California) (Reeves et al. 1992). In some areas, populations are reduced through government-sponsored culls (Norway) or commercial harvest (Iceland).

The population of common seals in the UK cannot be estimated very accurately but humans have historically hunted the common seal in great numbers. The Seal Conservation Act of 1970 gives a degree of protection as shooting is outlawed during the breeding season, however if a seal is deemed to be interfering with fishing nets, it can legally be shot at any time under the 'Fisheries Defence Clause' (5). In 1988 a disease caused by the newly emerged phocine distemper virus killed about 3,000 of the UK's common seals. Such drastic population crashes seem to be a natural occurrence, and little can be done to prevent them (3). Common seals are also susceptible to oil and chemical pollutants (3).

Biological Research Needs: 1. Worldwide monitoring of population trends in harbor seals and other sympatric marine mammals. 2. Focused biological research on potential causes of population declines in specific regions. 3. Regional research on global changes and impacts that are in the marine ecosystem, particularly in the Bering Sea. 4. Long-term viability and recovery studies.

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: Protected by the Marine Mammal Protection Act (1972) in the United States, but effective management plans have not been developed (Hoover 1988). Many haulout areas are protected by their designation as marine sanctuaries and wildlife refuges. Open water hatitat, however, is not protected. Protected in British Columbia by the Canadian Federal Fisheries Act (1970).

Needs: 1. Minimize all incidental take and disturbance. 2. Eliminate driftnet fisheries that occur in seal feeding and movement areas. 3. Regulate fisheries take of fish resources known to be important to the maintenance of healthy seal populations.

A number of key UK pupping and haul-out sites have been suggested as candidate Special Areas of Conservation (9). It has been recommended that human access to breeding sites could be restricted to reduce disturbance. Guidance notes on monitoring techniques for this species have been produced by the Joint Nature Conservation Committee, the Government's wildlife advisor (9).

Harbor seals often interfere with commercial fisheries, eating the fish that have been caught in nets and becoming trapped in the nets themselves.

Harbor seals are hunted primarily for their skins, oil, and meat. They can also be used in the production of jewelry and trinkets and as meat for mink feeding. Phoca vitulina can also serve as tourist attractions at aquariums and can be used in experimental research.

Positive Impacts: food ; body parts are source of valuable material; ecotourism

Comments: Long subjected to subsistence and bounty hunting and commercial harvest for pelts (see Reeves et al. 1992 for details). Large numbers continue to be killed in some areas (e.g., Iceland, Norway).