Species Fact Profile: Harbor Seal (Phoca vitulina)

                                                               Harbor (Common) Seal

                                                          Phoca vitulina (Linnaeus, 1758)

Range: Coastal Atlantic and Pacific Oceans in Northern Hemisphere (arctic, sub-arctic, and temperate waters), as far north as Greenland and Russia and as far south as Mexico, Portugal, and Japan

Habitat: Shallow coastal coves and bays (average depth of 90 meters – can be found in deeper water) and estuaries, inter-coastal islands, adjacent beaches.  Glaciers used for breeding

Diet: Fish, Cephalopods, Crustaceans

Social Grouping: Solitary, form small, loose mixed-sexed groups during pupping and molting seasons

Reproduction: Breed in the water, with males displaying for females using vocalizations and dives.   Largely monogamous, though some males may mate with multiple (up to 5) females.  Single pup born every season, twins have  been reported.  Implantation is delayed for 2.5 months after copulation, then resumes for an 8 month gestation period.    Births occur on land or close to shore in an attempt to keep pups safe from aquatic predators.    Females sexually mature at 3-4 years old, physically mature at 6-7 years old.  Males sexually mature at 4-5 years, physically mature at 7-9 years.

Lifespan: 40-45 Years

      Conservation Status: IUCN Least Concern 

• Body length 160-190 centimeters, weigh 60-170 kilograms.  Males grow larger than females.  Large, round head with a blunt snout, no external ears, narrow nostrils, and large whiskers.  Long flat flippers each have five webbed digits, used for propulsion in association with the trunk. 
• Two color phases – the light phase consists of a yellowish coat with small pale spots ringed in black.  The dark phase has a black coat with dark spots with light rings.  Differences are caused by variation in the concentration of melanin in the skin, with some variation being season or due to annual abundance of prey.  Some appear almost pure white
• Males may engage in combat on land, establishing territories in areas of high female traffic. 
• Unlike other seals, harbor seals shed their downy coat (lanugo) before parturition and are born with the same coat of fur as the adults.  This allows them to enter the water at birth, though they often ride on their mother’s back in the water.  Milk is 50% fat, allowing pups to grow rapidly.  Pups are weaned at 4-6 weeks, with their mothers breeding again immediately after. 
• They do not migrate, but may disperse a few hundred kilometers for foraging and breeding opportunities, but usually stay within 50 meters of their haul out site.  Haul out onto land or ice for a variety of reasons, most importantly for the molt (usually 2-3 months after weaning).  On land, often seen in a “banana” position with the head and rear curved upwards
• Can dive down over 420 meters and remain underwater for nearly half an hour, but most dives are a fraction of that depth and time.  When diving, their heart rate drops from 80-120 beats per minute to as low as 3-4 beats per minute.  Some dives are “V” shaped, with seals quickly swimming down deeply and then turning back to the surface.  Others are “U” shaped, with seals getting to a cruising level and then swimming for a while.  Seals may learn their preferred style of diving from their mothers.
• Thick layer of blubber provides thermoregulation and nutrient reserve (especially useful for the molt, when they can’t go in the water).  During the winter, blubber may make up 30% of their body weight.  They have a higher metabolic rate than other mammals of the same size
• Predators include large sharks, orcas, and polar bears.  On land, they are vulnerable to coyotes and other terrestrial predators.  Pups may be vulnerable to eagles and ravens
• Five subspecies: Eastern Pacific (P. v. richardii), Kuril, or Western Pacific (P. v. stejnegeri), Eastern Atlantic (P. v. vitulina), Western Atlantic (P. v. concolor), and the Ungava, or Seal Lake (P. v. rmellonae), found only in a few lakes and rivers in northern Quebec in Canada.  Some authorities only acknowledge two subspecies – Atlantic and Pacific
• Historically have been hunted by humans for their blubber, meat, fur, and skin, and still are by some traditional indigenous communities.  
• As late as 1960, state-sanctioned bounty hunters in Washington and Oregon culled harbor seals as potential competitors for commercial fishermen (still legal under some circumstances in some countries, such as Norway, Canada, and the United Kingdom).  Sometimes taken as bycatch by fishermen
• Threats include entanglement in fishing nets and lines, pollution through oil spills and chemical contamination, vessel collisions, and habitat degradation.  Seals are popular tourist attractions, and may be subject to illegal feeding or harassment.  Some populations have been lost due to disease, such as phocine distemper virus.