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,
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.
A harp seal pup resting
sign warns walkers to keep clear
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, 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 (perhaps 600 feet) and warn other beachgoers of its presence. By passing
on a chain of information, the seal may rest protected until the next tidal
In Massachusetts, it is a good idea to report a seal stranding (if you feel the
animal is in need or danger) to the Cape Cod Stranding Network at (508) 743-9548
(on Cape Cod) or the New England Aquarium, Boston at (617) 973-5247 (24 hour
paging system). Note the seal’s condition (even if dead), location and the tide.
CCSN and the NEAq can provide rehabilitation, if needed, and can gather
important information about species that are poorly understood.
To this day the over seventy different species of whale are divided between two
suborders: the Odontocetes (“toothed whales") and the Mysticetes (“mustached
whales”) or baleen whales. Representatives of both suborders can be found on
Gulf of Maine and reflect this diversity.
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