Harbor Seal

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). Females are generally smaller than males.

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 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. Harbor seals frequently congregate in harbours, bays, sandy intertidal zones, and estuaries in pursuit of prey fish such as salmon, menhaden, anchovy, sea bass, herring, mackerel, hake, cod, whiting and flatfish, and occasionally shrimp, crabs, mollusks, octopus, 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. Harbor seals have been recorded to attack, kill and eat several kinds of ducks.

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. Both courtship and mating occur under water. Researchers have found males gather under water, turn on their backs, put their heads together, and call to attract females ready for breeding. Pregnancy rate of females was 92% from age 3 to age 36, with lowered reproductive success after the age of 25 years. Birthing of pups occurs annually on shore. The timing of the pupping season varies with location, 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. The single pups are born well developed, capable of swimming and diving within hours. …