Common Seal, Phoca vitulina
The common seal (Phoca vitulina), also known as the harbor seal or harbour seal, is a true seal in the Phocidae family. It can be found in the northern Pacific, Atlantic, Baltic, and North Seas along the coastlines in these areas. This species holds five recognized subspecies, although the Western Atlantic common seal subspecies is questionably classified.
The common seal can reach an average length of up to 6.1 feet and a weight between 120 and 370 pounds. The fur can vary in color from tan to grey to black. Depending upon the fur color, the spots that occur along the body can be light or dark in appearance, creating a unique pattern for each seal. The body is stout and the flippers are short, and as a true seal, it does not have ears, instead bearing two canals near the back of the eyes.
The common seal prefers to spend much of its time on or near the coast, returning to previously used resting sites. These typically occur on rocky or rugged shores, but can also be found on sandy coastlines. It will swim up to thirty-one miles in search of abundant feeding grounds, sometimes moving through freshwater streams and rivers. This species gathers in groups, particularly in sandy areas, harbors, or estuaries in search of food. Its diet consists of many species of fish such as sea bass, anchovy, cod, herring, and flatfish. It will occasionally consume shrimp, squid, mollusks, and crabs.
Although the common seal is sociable, it does not gather in large groups like other seal species. Groups can be seen hauling out on the shores, typically venturing only 12.4 miles into the water. Despite this preference for land, courtship and breeding occur underwater, and it is thought that each seal can mate with many individuals. Studies have shown that males will gather underwater and sing to females in order to seek a mate. Pregnancy can last up to nine months, after which one pup is born on the shore. Pups are raised at different times, depending upon the area of their range. In areas found at lower latitudes, pupping occurs in February, while in areas located at higher latitudes pupping occurs in late July. The pups weigh an average of 35.2 pounds at birth and grow rapidly over the next four to six weeks while nursing on their mother’s fatty milk. Breeding occurs again shortly after pups are weaned. After breeding, the common seal will begin molting its fur, and it will spend most of its time on land during this period. Young individuals will molt first, while adult males will molt last.
The common seal is estimated to number around five to six million worldwide. Despite these large numbers, populations in the Baltic Sea, Hokkaidō, and Greenland are threatened. Some local populations have been eradicated due to disease and human encroachment. In Norway, Canada, and the United Kingdom, seal hunting is allowed if the seals threaten fisheries but commercial hunting has been made illegal. These seals can be caught accidentally or for food consumption, and along the Norwegian coastline, accidental catching is the cause of death for forty-eight percent of pups. The time spent on land is extremely important to the survival of the common seal. It will avoid areas with human presence, and sometimes refuse to haul out if humans are in the area, so this can be a major threat to the species.
The common seal has been protected by the 1970 Conservation of Seals Act in the United Kingdom and is protected in the United States by the Marine Mammal Protection Act of 1972. Because of this, common seals on the east coast of the United States have been able to reclaim areas of their former range, including Florida. The common seal appears on the IUCN Red List with a conservation status of “Least Concern.”
Image Caption: Common Seal. Credit: Andreas Trepte/Wikipedia (CC BY-SA 2.5)