Phoca vitulina Linnaeus 1758

14.

Harbor Seal

Phoca vitulina

French: Phoque commun / German: Seehund / Spanish: Foca moteada

Other common names: Common Seal, Harbour Seal; Eastern Atlantic Harbor Seal (vitulina); Western Atlantic Harbor Seal (concolor); Eastern Pacific Harbor Seal (richardii); Kuril Seal, Western Pacific Harbor Seal (stejnegeri)

Taxonomy. Phoca vitulina Linnaeus, 1758,

“in mari Europzo.” Restricted by O. Thomas in 1911 to “Mari Bothnico et Baltico.”

Some authors recognize a subspecies, mellonae (Seal Lakes or Ungava seal), from lakes and rivers of Ungava Peninsula in Canada, but it 1s not included here. The four subspecies of P. vitulina, two in the North Pacific Ocean and two in the North Atlantic Ocean, are distinguishable based on morphology and genetics, but geographical boundaries separating richardii from steynegeri (North Pacific) and vitulina from concolor (North Atlantic) are not precisely known. Four subspecies recognized.

Subspecies and Distribution.

P.v.vitulinaLinnaeus,1758—NEAtlanticOceanincludingSvalbardStoNWFrance(Brittany),withoccasionalsightingsasfarSasNPortugal;Wboundaryuncertain,perhapsIceland.

P.v.concolorDeKay,1842—NWAtlanticOcean,frommid-AtlanticUSAtotheCanadianArcticandEtoGreenland;Eboundaryuncertain,perhapsIceland.

P. v. richardGray, 1864 — NE Pacific Ocean, from Aleutian Is through the Gulf of Alaska (including Iliamna Lake) S to the coast of Baja California (N Mexico); contact zone with stejnegert may occur in W Alaska Peninsula-E Aleutian Is.

P. v. stejnegeri Allen, 1902 — NW Pacific Ocean along the coast of Russian Far East, from Kamchatka, the Kuril Is to N Japan (Hokkaido) and E to the Aleutian Is; contact zone with richardii may occur in E Aleutian Is—W Alaska Peninsula.

Descriptive notes. Total length c.140-190 cm (males) and ¢.120-170 cm (females); weight ¢.100-140 kg (males) and c.80-120 kg (females). Newborns are 75-100 cm in length and weigh 8-12 kg. Harbor Seals are moderate-sized phocid carnivores, with rounded heads. Average length varies among populations; the largest Harbor Seals occur near the Aleutian Islands and northern Japan and the smallest in the northern Gulf of Alaska. Pelage, just after molt, ranges from silver background with scattered black spots and blotches to black background with scattered lighter rings and splotches; there is some variation between these two extreme forms. There appears to be a cline in color pattern, with lighter forms dominating northern latitudes and darker forms more common in the south. Short pelage of the Harbor Seal fades to light tan to brown for much of the year in southern parts of its distribution and, to a lesser extent, farther north. Adult male Harbor Seals can be slightly larger than adult females, and those in the Pacific Ocean are larger than those in the Atlantic Ocean. Offspring are sometimes born with long creamy white lanugo (fine, soft hair) that is shed shortly after birth, but in most areas, lanugo is shed in utero.

Habitat. Resting habitat on intertidal rocks and reefs, mudflats and sandbars, sandy and pebbly beaches, and seasonal pack ice and fastice (ice fastened to land) in some areas. Harbor Seals give birth on sandy and pebbly beaches. Primary habitat is along outer continental and island coastlines and in bays and harbors, but occasionally on offshore islands. Harbor Seals mainly forage in relatively shallow coastal or near-island habitats, although they can feed at considerable depths; dives of up to 800 m have been recorded.

Food and Feeding. Harbor Seals have a very diverse, geographically variable diet, but they generally prey on abundant and easily available foods so a few species tend to dominate diets at any one location and time of year. Prey includes epibenthic and small schooling fish (Gadidae, Clupeidae, Osmeridae, Ammodytidae, Cottidae, Salmonidae, and a variety of flatfish), octopuses, squid, and crustaceans. Harbor Seals hunted for prey in lagoons and estuaries and bays, near-shore kelp beds, and sometimes deeper, offshore sandy-bottom habitats.

Breeding. Timing of births of Harbor Seals varies greatly geographically. They are born in March-April in Baja California (Mexico) and southern California (USA) and then progressively later farther north. Females in Oregon and Washington (USA) give birth in May-June and those in the Aleutian Islands in June-July. In the North Atlantic Ocean, females give birth in May-July, depending on region. Offspring are nursed for 3-4 weeks and then abruptly weaned and abandoned. Female Harbor Seals mate just before or after they wean their offspring. Non-parturient mature females come into estrus and mate a bit earlier. Copulations evidently occur only in the water. Adult male Harbor Seals patrol haul-out areas and visually, vocally, and physically threaten other adult males, and some displays may function to attract females. After females are impregnated, the embryo develops briefly and then is then dormant and free-floating until it attaches to the uterine wall and development resumes about two months later. Full gestation is about eleven months, but most fetal growth occurs during the last eight months or so. Femalesare sexually mature at 3-6 years old and males at 5-7 years old. Longevity is typically 35 years for females and 25 years for males, but it is lower for Harbor Seals in the Pacific Ocean at ¢.30 years for females and c¢.20 years for males.

Activity patterns. Harbor Seals frequently haul-out to rest on land or intertidal reefs, mudflats, and sandbars; they haul-out daily in some seasons but less often and for briefer periods in autumn and winter. During these resting bouts, they are vigilant and scan the area, evidently for potential terrestrial predators or human intruders. Although Harbor Seals are generally very sensitive to human presence and flee quickly to the water, they have become relatively tame and approachable in some areas like at Children’s Cove in downtown La Jolla, California, USA. When in the water, they appear to dive and forage continually for up to 15-20 minutes at a time, depending on depth of water and type of marine habitat. Harbor Seals appear to be solitary when foraging. Offspring are precocial and can swim at birth. Most nursing appears to occur on land, but offspring in most areas accompany females on daily tripsto sea. In a few locations, females evidently leave their offspring on the beach while they forage for brief periods. Harbor Seals molt in April-August, depending on geographical location, age, and sex. They haul-out more often and spend more time ashore when molting, which lasts c.2-3 weeks.

Movements, Home range and Social organization. Harbor Seals are thought to live and forage relatively near their haul-out sites, although movements or dispersal of tagged individuals, particularlyjuveniles, of several hundred kilometers have been document ed. There is no evidence of seasonal migration. Harbor Seals are gregarious and can occur in groups of hundreds, and sometimes several thousand, especially when molting in spring and summer, at particular terrestrial haul-out sites and mudflats and sandbars. Nevertheless, they are not particularly social, and most interactions between them on shore are brief visual and vocal threats to keep some distance between them.

Status and Conservation. Classified as Least Concern on The [UCN Red List. In 2013, the population of the “Eastern Pacific Harbor Seal” (P. v. richardii) in the freshwater Iliamna Lake, Alaska, was petitioned to the listed as a Distinct Population Segment under the US Endangered Species Act. Harbor Sealslive along coasts of western North America from Baja California north through waters of California, Oregon, and Washington and the eastern Aleutian Islands; their distribution continues through the central and western Aleutian Islands, south to Japan and north to Kamchatka and into the Sea of Okhotsk; and they also range into the eastern Bering Sea to Nome, Alaska, and the Pribilof Islands and in the western Bering Sea to the Commander Islands. In the eastern Atlantic Ocean, they are present in Iceland and Svalbard, and along the coasts of Norway, the North Sea, the British Isles, northern France, and into the southern Baltic Sea. In the western Atlantic Ocean, they occur along the coast of south-western Greenland and then range from south-western Baffin Island south to Massachusetts (USA), with occasional wanderers as far south as Florida. A relatively large colony occursat Sable Island off Nova Scotia, and a small population of 120-600 individuals inhabits freshwaters in the Ungava Peninsula. Harbor Seals have been hunted for food, oil, and skins for centuries by aboriginal cultures and more contemporary coastal communities, to different extents, throughout their extensive distribution. They were killed in large numbers in some areas in the 20" century for bounty because of perceived conflict with commercial fisheries. Outbreaks of distemper-like viruses greatly reduced populations of Harbor Seals in parts of Europe and the western North Atlantic Ocean in the 1980s and 1990s. Global population of Harbor Seals has been loosely estimated at ¢.500,000 individuals, with ¢.300,000 individuals in the North Pacific Ocean, including ¢.160,000 individuals in waters of Alaska (where numbers have greatly declined in the Aleutian Islands from undetermined causes).

Bibliography. Baird (2001), Bigg (1969, 1981), Boveng et al. (2003), Burns (2009), Dietz et al. (1989), Hayes et al. (2004), Jeffries et al. (2003), Small et al. (2008), Stewart & Yochem (1994, 2000), Temte et al. (1991), Thomas (1911), Thompson & Harkénen (2008b), Yochem et al. (2000).