The word pinniped (fin footed) refers to animals of like appearance, not relatedness. Pinnipeds describe any carnivorous, amphibious mammal with front and hind appendages modified into flippers. Seals, sea lions and walrus, with over 30 species worldwide, fit the description, and are often lumped together.
The evolutionary history of pinnipeds is still under debate; seals, sea lions, and walruses may or may not be related, even though they look alike, and scientists are divided into two basic camps. Pointing to some good genetic evidence, the monophyletic camp of the discussion believes there is a common ancestor to all the species. The biphyletica camp, however, believes that convergent evolution – a process by which different organisms adapting to similar environments wind up with similar results – is at play. Biphyletics find enough morphological differences between seals and sea lions that a dog-like and bear-like ancestry, respectively, is apparent. Both camps are equally troubled by the walrus, an animal that has characteristics of seals and sea lions.
Whatever the argument, at least three families of pinnipeds seem real enough today: Otaraiidae, or eared seals such as sea lions; fur seals, Phocidae, or true seals, which have no external ear; and Odobendidae, or walrus, which still retain an ambiguous place in the pinniped ranks.
Seals on the Bank
Otaraiids (eared seals) are not found anywhere in the North Atlantic. And, it is debatable whether the walrus ever made consistent use of Stellwagen Bank before being hunted to commercial extinction during the 18th century (tusks have been dragged up by fishermen on Stellwagen). Only phocids (true seals) are commonly found on Stellwagen Bank.
Of the five species of phocids found with any frequency on Stellwagen Bank, two (harp, hooded) are found only sporadically, but with increasing frequency. The ringed seal is always rare in the area while some gray and harbor seals can be found here year-round. Each species uses the Bank and the surrounding coast in different ways, but they do share many characteristics.
All seals on the Bank give birth to one pup on land or ice, nurse them on rich milk, and come ashore occasionally to rest or sleep. The seals’ large eyes help them gather available light while hunting and diving. All propel themselves with a side-to-side, sculling motion of their hind flippers and steer with their front flippers and flexible neck. Long, sensitive whiskers help them find prey in darkness. On land, they move by lurching forward on their bellies, gripping with claws on their front flippers, and can be surprisingly quick.
Visitors to the coast sometimes encounter seals “stranded” on beaches. Unlike whales, seals are well adapted for dealing with the land and actively come ashore for a number of reasons, including rest, mating, nursing and pupping. Often a seal alone on the beach is a pup temporarily parked there by its mother, who is offshore hunting.
Unafraid, pups often make no attempt to return to the water at the approach of people. The pup’s mother, however, will not come back ashore to retrieve the pup while humans or dogs are present. With burgeoning human and seal populations, interactions between the two are becoming more frequent. It is not safe to assume that every seal on the beach is in need of human care. Seals may be finding it more and more difficult to find a peaceful place to rest.
If you do find a seal on the beach, please follow Federal seal viewing guidelines. It is best to give it plenty of space and move on as quickly as possible. Do NOT try to touch the animal. Seals have powerful jaws and very sharp teeth that are often covered with bacteria that can cause a painful condition in humans called “seal finger” Seals are also protected from harassment by the Marine Mammal Protection Act of 1972. Do not attempt to either surround or feed seals that you find on the beach. The more often a seal has to watch a beach-goer, the less time it has for resting. If at all possible, stay in the vicinity, far enough away from the seal to still see it (a minimum of 150 feet) and warn other beachgoers of its presence. By passing on a chain of information, the seal may rest protected until the next tidal cycle. By passing on a chain of information, the seal may rest protected until the next tidal cycle.
On Cape Cod, it is a good idea to report a seal stranding (if you feel the animal is in need or danger) by calling the International Fund for Animal Welfare (IFAW) at (508) 743-9548 or call the Greater Atlantic Region Fisheries Office hotline for anywhere else in Massachusetts (866-755-6622). Note the seal’s condition (even if dead), location and the tide.