Harbor seals populate the shallow waters of coastal areas, bays, rocky islets, estuaries, and even freshwater lakes. They are typically seen near piers and beaches, as well as on intercoastal islands. They are more common in relatively cold marine waters that lack annual sea ice coverage. However, tidewater glaciers are utilized for shelter, breeding, and occasionally transportation. They forage at an average depth of 91 m, but can go as deep as 427 m.
Range depth: 427 (high) m.
Average depth: 91 m.
Habitat Regions: temperate ; saltwater or marine ; freshwater
Aquatic Biomes: coastal
Other Habitat Features: estuarine ; intertidal or littoral
Predators of harbor seals inlcude larger species like sharks (Selachimorpha), killer whales (Orcinus orca), and polar bears (Ursus maritimus). Haul out sites help reduce predation by shortening the time they spend in water, yet there is still danger on land. For example, coyotes (Canis latrans) may prey on pups when their mothers are foraging. Humans (Homo sapiens) also prey on harbor seals in some areas of the Arctic.
Known Predators:
Harbor seals are physically adapted to maximize propulsion while diving. Their large round heads that lack external ears, although their middle ear bones are large. Rather than exhaling before diving, they essentially stop breathing underwater and their heart rate slows, resulting in conservation of oxygen in their bodies. They have narrow nostrils that easily close during swimming. Their flippers are long and flat, each made up of five webbed digits. Speed and agility in the water is enhanced by use of their hind limbs and flexible side-to-side movements of their trunks. Adult males are typically larger than females, measuring 160 to 190 cm in length, and weighing 80 to 170 kg. Females range from 160 to 170 cm long and weigh 60 to 145 kg.
Although various regions differ slightly, harbor seals are monomorphic. Individuals with a yellowish coat covered in small pale ringed black spots are characterized as being in the “light phase”. The “dark phase” seals have a black coat containing dark spots with light rings found primarily on their dorsum. Their varying color patterns are a result of differing concentrations of melanocytes in the epidermis. Their fur protects their skin from damage while on land, and is kept moist by secretions from sebaceous glands.
Thick layers of subcutaneous fat provide energy and insulation, giving them a higher resting metabolism rate that is 1.7 to 2.2 times higher than other terrestrial mammals their size. Another trait that separates harbor seals from other mammals is their vibrissae (whisker) structures, whose follicles are surrounded by 3 blood sinuses as opposed to 2.
Average mass: 80 to 170 kg.
Average length: 160 to 190 cm.
Sexual Dimorphism: male larger
Other Physical Features: endothermic ; bilateral symmetry
Average mass: 115000 g.
Average basal metabolic rate: 73.29 W.
Harbor seals in the wild are estimated to reach an average lifespan of 40 years. In captivity, the longest recorded lifespan was 47.6 years.
Range lifespan
Status: captivity: 47.6 (high) years.
Average lifespan
Status: wild: 40 years.
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.
Harbor seals are the pinniped with the largest geographical range, encompassing coastal areas of the east and west Pacific and Atlantic Oceans in the Northern Hemisphere. Their range spans from the western Pacific Ocean coast north towards the Gulf of Alaska and to the southeastern Bering Sea. The western Atlantic Ocean harbor seals are distributed from the French coast to the North Sea and northward to the Barents Sea, as well as along the Atlantic coast of North America. Although they inhabit a large range of coastal and insular regions, the Pacific and Atlantic colonies are separated by large intervals with uncertain boundaries and five subspecies are recognized.
Biogeographic Regions: nearctic (Native ); palearctic (Native ); arctic ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )
Other Geographic Terms: holarctic
Harbor seals are carnivores that consume mostly fish. Despite regional variation in individual diets, the overarching goal of harbor seals is to keep foraging efforts low by eating what is abundant and easily caught. Adults eat mostly fish, consuming the fish whole or head first. Preferred medium-sized fish species include codfish (Gadus), hake (Merluccius merluccius), mackerel (Scombridae), and herring (Clupea pallasii pallasii). They also eat octopus (Octopoda) or squid (Teuthida), as well as crustaceans (Crustacea) such as crabs (Brachyura) and shrimp. Because newly weaned pups have poorly developed diving abilities, their primary diet consists of crustaceans that are easier to catch. Harbor seals weighing 100 kg eat about 5 to 7 kg of food per day. They will dive up to 427 m for a potential meal.
Animal Foods: fish; mollusks; aquatic crustaceans
Primary Diet: carnivore (Piscivore )
Harbor seals are hosts to many parasites. These include nematodes such as Pseudoterranova decipiens and Contracaecum osculatum and cestodes such as Anophryocephalus and Diplogonoporus. Although many parasites found living on the seals are normally harmless, seals that acquire pathogens when their immune systems are repressed could become deadly. The parasites could also pass bacteria and/or viruses that could make them very ill. For example, Leptospira interrogans is the bacterium responsible for the most recorded deaths in all pinnipeds.
Commensal/Parasitic Species:
Harbor seals are hunted for their blubber, meat, fur, and skin. They are also a potential source of ecotourism value.
Positive Impacts: food ; body parts are source of valuable material; ecotourism ; research and education
Harbor seals interfere with some commercial and local fisheries. They lower the available fish supply for consumption, and can also become entangled in nets. Entanglement usually leads to the nets breaking which releases fish that could have been caught and utilized by the fisheries.
The total population of harbor seals has been increasing since around the 1970s. However, major die-offs have occurred in recent years where thousands of seals have died from diseases not previously known to be a problem. Because they are a coastal species, they are particularly vulnerable to pollution. Their status on the IUCN Red List is "least concern." However, two subspecies are currently on the brink of extinction. First is the subspecies population Phoca vitulina stejnegeri in Japan that has been steadily declining due to excessive hunting since the 1980s. Secondly, the subspecies Phoca vitulina mellonae that lives in the Ungava Peninsula in Canada have very low population numbers of 120 to 600 seals. They are the subspecies most at risk due to low genetic variation and are also negatively impacted from hydroelectric developments. No reports of efforts to conserve these two subspecies have been found.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Harbor seals are extremely alert and appear to be continuously aware of their surroundings, even when in captivity. In comparison to related seals, they are known to be less vocal. Their detected sound frequencies range from 0.1 to 10 kHz. Their relative “quietness” may be an adaptation to avoid predication. The noises they produce have been associated with sounding more like burping, grunting, and yelping. Harbor seals are recognized to be a profoundly playful species in both pups and adults. They often play by themselves and with other objects such as kelp. They have large eyes with corneas that are flattened that allow them to take in more light and see brighter images in dark water. Their sensitive whiskers acoustically detect sound waves, which is useful for catching prey. Another behavior they are known for is slapping their flippers vigorously against the water’s surface; the motive behind such action is still unknown. With such a wide geographical range, behaviors may vary between regions.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Harbor seals mate in aquatic habitats, and males attempt to attract potential mates in a variety of ways. These include showing off vocal or diving capabilities and direct competition between males. The latter involves intense fighting near haul out sites and areas of high female abundance. Males may also establish territories in areas of high female traffic to maximize contact with potential mates. Actual mating occurs in water, as is typical of seal species, which makes it difficult to observe and fully understand their mating systems. Harbor seals are considered mostly monogamous, but there have been reports in literature of slight polygamy with males mating with multiple females, but with a maximum of five successful fertilizations.
Mating System: polygynous
Female harbor seals typically give birth to a single pup every season with pregnancy rates that are about 85%. Twins have occasionally been reported. Once a female becomes fertilized, there is a delay in implantation that lasts about 2.5 months. Then implantation resumes and develops for 8 months before birth. The total gestation period lasts about ten and a half months. Birthing occurs close to the shore or on land, which appears to be an adaptation to isolate females and pups from aquatic predators.
Depending on regional and environmental factors, all sub-species of harbor seal pups are typically born in the same 10 week window lasting from late winter to summer. Newborns weigh 8 to 12 kg. While some seals retain a fine, downy coat of hair called lanugo after birth, harbor seal pups shed their lanugo well before they are born. At birth, the pups' fur is the same texture as that of the adults, which allows them to safely enter cooler waters. However, adult fur coats don't develop until the end of the first summer. Pups are weaned and independent after 4 to 6 weeks, and mating for the following year commences immediately afterward. Female harbor seals reach sexual maturity by age 3 to 4, and physical maturity by age 6 to 7. Male harbor seals don’t reach sexual maturity until age 4 to 5, and physical maturity until 7 to 9 years of age.
Breeding interval: Harbor seals usually breed once per year, normally in late winter to summer.
Breeding season: Breeding occurs during a 10 week period.
Range number of offspring: 0 to 2.
Average gestation period: 10.5 months.
Range weaning age: 4 to 6 weeks.
Range time to independence: 4 to 6 weeks.
Average age at sexual or reproductive maturity (female): 3-4 years.
Average age at sexual or reproductive maturity (male): 4-5 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous ; delayed implantation ; embryonic diapause
Average birth mass: 11000 g.
Average gestation period: 253 days.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 1460 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 1095 days.
Female harbor seals invest more effort in parental care than do males. Within the first hour of birth, mothers eagerly bond to establish recognition, which is critical to the success or raising a harbor seal. Pups are generally nursed for 4 weeks with milk containing around 50% fat from their mothers. This high fat content results in rapid growth. For 4 to 6 weeks until the pups are weaned, they cling to their mothers' backs in the water.
Parental Investment: female parental care ; pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
The harbor (or harbour) seal (Phoca vitulina), also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinniped (walruses, eared seals, and true seals), they are found in coastal waters of the northern Atlantic and Pacific oceans, Baltic and North seas.
Harbor seals are brown, silvery white, tan, or gray, with distinctive V-shaped nostrils. An adult can attain a length of 1.85 m (6.1 ft) and a mass of up to 168 kg (370 lb). Blubber under the seal's skin helps to maintain body temperature. Females outlive males (30–35 years versus 20–25 years). Harbor seals stick to familiar resting spots or haulout sites, generally rocky areas (although ice, sand, and mud may also be used) where they are protected from adverse weather conditions and predation, near a foraging area. Males may fight over mates under water and on land. Females bear a single pup after a nine-month gestation, which they care for alone. Pups can weigh up to 16 kg (35 lb) and are able to swim and dive within hours of birth. They develop quickly on their mothers' fat-rich milk, and are weaned after four to six weeks.
The global population of harbor seals is 350,000–500,000, but the freshwater subspecies Ungava seal in Northern Quebec is endangered.[1] Once a common practice, sealing is now illegal in many nations within the animal's range.
Individual harbor seals possess a unique pattern of spots, either dark on a light background or light on a dark. They vary in colour from brownish black to tan or grey; underparts are generally lighter. The body and flippers are short, heads are rounded. Nostrils appear distinctively V-shaped. As with other true seals, there is no pinna (ear flap). An ear canal may be visible behind the eye. Including the head and flippers, they may reach an adult length of 1.85 m (6.1 ft) and a weight of 55 to 168 kg (120 to 370 lb).[3] Females are generally smaller than males.
There are an estimated 350,000–500,000 harbor seals worldwide.[1] While the population is not threatened as a whole, the Greenland, Hokkaidō and Baltic Sea populations are exceptions. Local populations have been reduced or eliminated through disease (especially the phocine distemper virus) and conflict with humans, both unintentionally and intentionally. Killing seals perceived to threaten fisheries is legal in Norway, and Canada, but commercial hunting is illegal. Seals are also taken in subsistence hunting and accidentally as bycatch (mainly in bottomset nets). Along the Norwegian coast, bycatch accounted for 48% of pup mortality.[4] Killing or taking seals has been illegal in the United Kingdom since 1 March 2021.[5]
Seals in the United Kingdom are protected by the 1970 Conservation of Seals Act, which prohibits most forms of killing. In the United States, the Marine Mammal Protection Act of 1972 prohibits the killing of any marine mammals, and most local ordinances, as well as NOAA, instruct citizens to leave them alone unless serious danger to the seal exists.
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The five proposed subspecies of Phoca vitulina are:
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Harbor seals prefer to frequent familiar resting sites. They may spend several days at sea and travel up to 50 km in search of feeding grounds, and will also swim more than a hundred miles upstream into fresh water in large rivers in search of migratory fish like shad and likely salmon. Resting sites may be both rugged, rocky coasts, such as those of the Hebrides or the shorelines of New England, or sandy beaches, like the ones that flank Normandy in Northern France or the Outer Banks of North Carolina.[1] Harbor seals frequently congregate in harbors, bays, sandy intertidal zones,[1] and estuaries in pursuit of prey fish such as salmon,[8] menhaden, anchovy, sea bass, herring, mackerel, cod, whiting and flatfish, and occasionally shrimp, crabs, mollusks, and squid. Atlantic subspecies of either Europe or North America also exploit deeper-dwelling fish of the genus Ammodytes as a food source and Pacific subspecies have been recorded occasionally consuming fish of the genus Oncorhynchus. Although primarily coastal, dives of over 500 m have been recorded.[9] Harbor seals have been recorded to attack, kill and eat several kinds of ducks.[10]
Harbor seals are solitary, but are gregarious when hauled out and during the breeding season, though they do not form groups as large as some other seals. When not actively feeding, they haul to rest. They tend to be coastal, not venturing more than 20 km offshore. The mating system is not known, but thought to be polygamous. Females give birth once per year, with a gestation period around nine months. Females have a mean age at sexual maturity of 3.72 years and a mean age at first parturition of 4.64.[11] Both courtship and mating occur under water.[12][11] Researchers have found males gather under water, turn on their backs, put their heads together, and vocalize to attract females ready for breeding.[13] Pregnancy rate of females was 92% from age 3 to age 36, with lowered reproductive success after the age of 25 years.[11]
Birthing of pups occurs annually on shore. The timing of the pupping season varies with location,[14] occurring in February for populations in lower latitudes, and as late as July in the subarctic zone. The mothers are the sole providers of care, with lactation lasting 24 days.[15] The single pups are born well developed, capable of swimming and diving within hours. Suckling for three to four weeks, pups feed on the mother's rich, fatty milk and grow rapidly; born weighing up to 16 kilograms, the pups may double their weight by the time of weaning.
Harbor seals must spend a great deal of time on shore when molting, which occurs shortly after breeding. This onshore time is important to the life cycle, and can be disturbed when substantial human presence occurs.[16] The timing of onset of molt depends on the age and sex of the animal, with yearlings molting first and adult males last.[17] A female mates again immediately following the weaning of her pup. Harbor seals are sometimes reluctant to haul out in the presence of humans, so shoreline development and access must be carefully studied in known locations of seal haul out.
In comparison to many pinniped species, and in contrast to otariid pinnipeds, harbor seals are generally regarded to be more vocally reticent. However, they do utilize non-harmonic vocalizations to maintain breeding territories and to attract mates during specified times of year,[18] and also during mother and pup interactions.[19]
Annual survival rates were calculated at 0.91 for adult males,[11] and 0.902 for adult females.[20] Maximum age for females was 36 and for males 31 years.[11]
The California population of subspecies P. v. richardsi amounted to about 25,000 individuals as of 1984. Pacific harbor seals or California harbor seals are found along the entire Pacific Coast shoreline of the state. They prefer to remain relatively close to shore in subtidal and intertidal zones, and have not been seen beyond the Channel Islands as a pelagic form; moreover, they often venture into bays and estuaries and even swim up coastal rivers. They feed in shallow littoral waters on herring, flounder, hake, anchovy, codfish, and sculpin.[21]
Breeding occurs in California from March to May, with pupping between April and May, depending on local populations. As top-level feeders in the kelp forest, harbor seals enhance species diversity and productivity. They are preyed upon by killer whales (orcas) and white sharks. Haul out sites in California include urban beaches and from time to time they can be seen having a nap on the beach in all of San Francisco Bay, which would include the conurbation of Richmond, Oakland, and San Francisco, the Greater Los Angeles area, which would include Santa Barbara, the city of Los Angeles itself, and Long Beach, and all of San Diego Bay, most famously beaches near La Jolla.[22][23][24][25][26][27]
Considerable scientific inquiry has been carried out by the Marine Mammal Center and other research organizations beginning in the 1980s regarding the incidence and transmission of diseases in harbor seals in the wild, including analysis of phocine herpesvirus.[28] In San Francisco Bay, some harbor seals are fully or partially reddish in color, possibly caused by an accumulation of trace elements such as iron or selenium in the ocean, or a change in the hair follicles.[29]
Although some of the largest harbor seal pupping areas are found in California, they are also found north along the Pacific Coast in Oregon, Washington, British Columbia and Alaska. Large populations move with the season south along the west coast of Canada and may winter on the islands in Washington and Oregon. Pupping is known to occur in both Washington and Oregon as of 2020. People are advised to stay at least 50m away from harbor seals that have hauled out on land, especially the pups, as mothers will abandon them if there's too much human activity nearby.[30]
Historically, the range of the harbor seal extended from the mouth of the St. Lawrence River and Greenland to the sandy beaches of North Carolina, a distance of well over a thousand miles (greater than 1600 km.) Evidence of their presence in these areas is consistent with both the fossil record as well as a few landmarks named for them during colonization: Robbin's Reef, off of Bayonne, New Jersey, gets its name from the Dutch word robben, meaning "seals". On the border between Canada and the US is an island known as Machias Seal Island, a place where today the harbor seal will occasionally visit but is now a sanctuary for puffins. Over the course of hundreds of years, however, the seal was wiped out steadily by being shot on sight by fishermen and by massive pollution. The evidence for this is found in documents all along the coast of New England which put a bounty on the head of every seal shot, as well as the accounts of harbormasters. New York City, when it was founded in the 1640s, was founded on top of an enormous estuary teeming with life that included the harbor seal. Oil in the 1800s started the process of pollution that was later compounded by even more toxic 20th century chemicals that included PCB's and dioxin. By the time of the 1972 Clean Water Act, New York Harbor was almost dead-almost no living thing could survive in it.[31] Approximately 300 miles to the north, Boston Harbor was equally polluted. Raw sewage had been dumped in the harbor since the late 1800s and the stench of fecal matter in the Charles River was overpowering, as evidenced by the song "Dirty Water" by the Standells, written in 1966. Flatfish, abundant in the area, had enormous tumors in their livers by the 1980s and the harbor seal was long gone, shot to oblivion.[32]
As of 2020, however, the seals have returned. They never were extirpated from Canada and certain pockets of the Maine coast, and thus an important mother population was created from whence the species could reclaim the home of their ancestors. Currently, they are sighted as far south as the barrier islands of North Carolina on a regular basis,[33] with Massachusetts being the southernmost point of known pupping areas along the Atlantic Coast.[34] Harbor seals move south from eastern Canadian waters to breed along the coast of Maine, Cape Cod, and the South Shore in Massachusetts in May and June, and return northward in fall. Others will head south from these areas to "vacation" in warmer waters, particularly young seals unable to compete with adults for food and territory; they do not return north until spring.
One park ranger in New York City, which is dead center of its West Atlantic range, says that "New York is like their Miami resort."[31] This refers to the habit of young seals leaving Cape Cod and even some Arctic waters to inhabit the harbor in winter. In 2018 the New York Post reported that the harbor is now "cleaner than it has been in 110 years,"[35] and since the first decade of the 21st century, the harbor seal has found the old turf of its ancestors to be a land of plenty and the water to be livable. Within sight of the New York skyline, known colonies of harbor seals are found on Hoffman[36] and Swinburne Islands[37] as well as portions of Red Hook[38] and Staten Island,[39] readily hauling out every from October until very early May. Known favorite foods of the seal are returning in grand numbers to New York Harbor as well as nearby New Jersey, from Raritan Bay all the way down the entire Jersey Shore, with schools of mossbunker regularly attracting harbor seals, their cousins the grey seals, dolphins and, most recently, whales.[40] Both the northern and southern shores of Long Island have a reliable population of harbor seals as well as greys, where they will take sand lance as well as some species of crab as part of their diet.
The harbor (or harbour) seal (Phoca vitulina), also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinniped (walruses, eared seals, and true seals), they are found in coastal waters of the northern Atlantic and Pacific oceans, Baltic and North seas.
Harbor seals are brown, silvery white, tan, or gray, with distinctive V-shaped nostrils. An adult can attain a length of 1.85 m (6.1 ft) and a mass of up to 168 kg (370 lb). Blubber under the seal's skin helps to maintain body temperature. Females outlive males (30–35 years versus 20–25 years). Harbor seals stick to familiar resting spots or haulout sites, generally rocky areas (although ice, sand, and mud may also be used) where they are protected from adverse weather conditions and predation, near a foraging area. Males may fight over mates under water and on land. Females bear a single pup after a nine-month gestation, which they care for alone. Pups can weigh up to 16 kg (35 lb) and are able to swim and dive within hours of birth. They develop quickly on their mothers' fat-rich milk, and are weaned after four to six weeks.
The global population of harbor seals is 350,000–500,000, but the freshwater subspecies Ungava seal in Northern Quebec is endangered. Once a common practice, sealing is now illegal in many nations within the animal's range.
