Size: Males measure at around 63-75 inches (160-190 cm) and females 63-67 inches (160-170 cm).
Weight: Males weigh between176 and 375 lbs (80-170 kg), while females are 132-320 lbs (60-145 kg).
Color – Variable from a brownish black to a silvery grey, the ventral sides are usually much lighter. They also have a pattern of spots which is unique to each individual.
Distribution & Subspecies
Eastern Atlantic common seals
Phoca vitulina vitulina
Europe to Western Asia
Pacific common seals
P. v. richardsi
Western North America
P. v. stejnegeri
P. v. mellonae
Western Atlantic common seals
P. v. concolor (controversial)
Eastern North America
They live in shallow waters in bays, coastal regions, estuaries, rocky islets, and freshwater. They use tidewater glaciers for shelter, transportation, and breeding. They are rather common in somewhat cold marine waters which do not have yearly sea ice coverage.
Harbor Seal Pictures
They are usually solitary but do congregate during the pupping and molting season. They do not exhibit any social structure during this time.
Harbor seals are diurnal.
They like to spend their resting periods usually in areas familiar to them. These sites are usually within 20 miles from the shore.
Although not migratory, they can spend many days at sea, traveling long distances to search for feeding grounds.
They molt once a year immediately after the breeding season with the youngest molting first.
Mating & Reproduction
Male harbor seals are believed to be monogamous. The female gives birth to pups once a year. The mating takes place underwater, thus negating the chance of studying that aspect. After a gestation period of around 9-10½ months, a single pup is born, although twin births have rarely been observed. The pupping season varies with location, with the seals inhabiting the colder subarctic regions giving birth in July, and those at lower latitudes in February.
Baby Harbor Seal
Harbor Seal Pup
The pups usually weigh at birth between 17-35 lbs. The mothers are usually the only ones looking after them. They are nursed for up to 6 weeks but grow quickly because of their mother’s rich and nutritious milk, doubling their birth weights by the time they are weaned, until which time, the offspring cling to the mother’s back when in the water. Males reach sexual maturity at 3 to 7 years of age, while females become mature at 3 to 6 years.
Females live longer than male harbor seals. The former may live for 30-35 years, while the latter only lives for 20-25 years.
Sounds & Communication
They communicate through yelps, grunts, and burps. They are a very alert creature and avoid making too much noise to be stealthy from predators.
They are carnivorous, with fishes like sea bass, anchovies, mackerel, flatfish, herring, whiting, and cod making up the majority of their diet. They also sometimes eat crabs, mollusks, shrimp, and squids.
Harbor Seal Skull
Harbor Seal Images
When underwater, harbor seals stop breathing so that their heart rate decreases leading to the conservation of energy. Also, they exhale before a deep dive which helps the oxygen accumulate into the muscles and blood, essentially reducing the oxygen content in the lungs.
Their four flippers assist them to move around in the water, with the hind pair propelling them forward, and the front two helping them steer themselves.
A higher metabolic rate compared to mammals of a similar size helps them produce body heat to keep their bodies warm.