Results tagged “pinnipeds” from PlanetGreen.org

Harboring Harbor Seals

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harborseal.jpgThere's a good reason why the harbor seal is also called the "common seal." They're found all over the northern hemisphere's coastlines, in the Pacific and Atlantic oceans and throughout the North and Baltic seas. They are also the most widespread pinniped, a term which refers to true seals, eared seals (sea lions and fur seals), and walruses. (Neither true seals nor walruses have ear flaps, known as pinnas.)

Harbor seals are true seals. They have small flippers that do not rotate and consequently have a hard time moving around on land. They rely on layers of blubber for warmth, buoyancy, and extra energy. The blubber also allows the seal's skin to be the temperature of the water surrounding it, while their core temperature, or how warm they are inside, is 100° F. They have large eyes, but most scientists think that their color vision is very bad, if existent. Harbor seals have better eyesight than humans underwater, but worse on land. Since blind seals have been found with pups in the ocean, scientists believe that sight is unimportant to harbor seals. Although they usually stay closer to the surface and come up for air once in ever three to seven minutes, they can dive 1,500 feet underwater and stay submerged for 40 minutes! Mostly, these seals catch fish, but sometimes when they've gone that deep they'll eat shrimp, crabs, mollusks, octopods, and squids.

Harbor seals spend approximately half of their time in the ocean, and the other half on land. Although they typically stay in the water only when feeding, they have been known to sleep in the water, too. Places where they regularly rest on land are called "haulouts," and the process of a seal climbing up onto the land is called "hauling out." Unfortunately, if people repeatedly disturb them they will abandon their haulouts or even their babies. Sometimes, seals dart into the sea as soon as they see or hear people. That's why beaches often post signs warning people to stay at least 100 feet away from the seals and use binoculars or cameras. Goat Rock Beach suggests 150. The Point Reyes National Seashore website advises visitors to come no closer than 300 feet.

To attract a mate, male seals will form a group, put their heads together and call the females. It is thought that the females select the strongest males. Although they can be seen at any time of the year, the best time to view harbor seals in California is probably from February to April, when they are having their babies. In the Arctic, they may wait until July! Young seals are called pups and usually born with a spotted coat. If you see a pup with a white coat, called a lanugo, it was born prematurely. (In the Arctic, the pups are born with the white fur but molt soon afterwards.)

sealsgoatrock2.jpgHarbor seals haul out on many beaches. We saw them in February on California's Goat Rock beach. (The origin of Goat Rock's name is disputed. There is a very large rock connected to the beach by a thin strip of land, and the most popular theory states that goats used to be permitted to graze on the rock because they were the only species surefooted enough to climb it.)

The Californian or Pacific harbor seal is a subspecies of harbor seal found along the entire coastline of California. In the San Francisco bay, some seals appear reddish. This unusual coloration is thought to result from tiny quantities of elements, such as iron or selenium, in the water.

Some field guides make it sound like it is very difficult to tell a harbor seal from a sea lion, but it is actually very simple. Harbor seals are usually light gray, and sea lions are dark brown. The sea lion is able to flip its flippers forward so that it can walk on land. For the most part, the seals lie on the beach, while the sea lions sit up on their front flippers and grunt. Additionally, studying a photo of any animal beforehand will help you identify it in the field.

The worldwide population of harbor seals is five or six million. Hunting seals is illegal throughout most of their range, but certain subspecies are threatened. Besides people disturbing them on beaches, the seals are caught in fishing nets and hit by boats. They are endangered by chemicals dumped in the water or released by power plants. Diseases such as the phocine distemper also threatened them. And while it is illegal in the United States to hunt harbor seals, if a seal is thought to endanger a fishery it can legally be killed. Happily, however, the numbers of harbor seals have been rising on the east coast of the US, and some have even been spotted in Florida. With care, these seals will continue to haul out throughout their widespread range.

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