The harbor seal, also known as the common seal, is the most widely distributed species of earless or true seals belonging to the Phocidae family. They inhabit the northern hemisphere from the Atlantic to Pacific Ocean to the Baltic Sea.
The common seal, by the scientific name of Phoca vitulina, is a member of the Phocidae family. It belongs to the tribe Phocini, alongside other members such as the spotted seal, the ringed seal and the Caspian seal. The species is divided into 5 subspecies on the basis of population isolation over a long period of time, which resulted in anatomical and behavioral differences. The 5 subspecies of common seals are: P. v. concolor, P. v. mellonae, P. v. richardsi, P. v. stejnegeri and P. v. vitulina.
Description of a harbor seal
The common seal is a medium sized true seal, with males being slightly larger than females. Males can reach 1.85 meters in length and can weigh up to 160 kg.
Each individual has a unique pattern of colors, from darker spots on a light background to light spots on darker backgrounds. The head is relatively round with a short snout. They have no pinnae or ear flaps, just like other true seals. The nostrils are V-shaped. The flippers are also shorter compared to many other seals.
Habitat and distribution
It is estimated that there are around 500,000 seals around the world, hence their name common seals. Harbor seal populations can be found in the coastal water of the Pacific Ocean, on Hokkaido Island, in the Baltic Sea, in the UK, Norway and Canada. Large populations can be seen on sandy or gravel beaches all throughout the northern hemisphere. The common seals are usually solitary, but they will gather in large numbers when hauling out, activities which include basking in the sun for thermoregulation, breeding and avoiding predators.
The common seal can travel as far as 50 km from the shore when hunting. These seals usually hunt fish such as anchovy, sea bass, cod, mackerel and flatfish. They may also feed on squid, shrimp, crab and other mollusks.
These seals haul out to rest as well as to mate. Courtship and mating has been observed to occur only underwater. Mating is most likely polygamous, where a male mates with several females. After a gestation of around 9 months, harbor seal females give birth to pups that can weigh 16 kg, pups that will rapidly grow thanks, to the high fat content of cow milk, and be weaned after 4 to 6 weeks.