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Communication
Seals can communicate underwater.
Their sounds are varied, from whoops, barks and moans to mating
calls. Some seals, including bearded seals, Weddell seals, and
walrus, sing songs that may last more than a minute.
Diet
Most seals eat fish or squid. However, the leopard seal in Antarctica
hunts penguins and other birds, other seals, fish, squid, krill
(small shrimplike creatures), and other invertebrates, as well
as feeding on carcasses of dead whales. They will attack humans
too, on the ice and divers in the water. Another unusual seal
feeder is the crabeater seal of the Antarctic because they eat
krill, sieving water through their teeth to trap the tiny krill
inside their mouth.
Sea lions generally eat fish. Walruses dive to the bottom and,
with the help of sensitive whiskers, search for molluscs, worms
and shellfish in the mud. An adult walrus can eat about 45 kg
a day.
Reproduction
All pinnipeds must come ashore to breed, give birth and suckle their young. Some species, such as elephant seals and sea lions, form large groups in the breeding season. These are called rookeries. The strongest males gather a harem, or group of females with which to mate. They allow less strong males to join the group. In these species, males are much bigger than females. The walrus breeds on ice islands, and dominant (strongest) males gather large harems. Walruses use their tusks to fight each other and to attract females. Male walrus use their large throat pouches to make sounds to attract females.
Other species, particularly those that breed on the ice, don't form harems, but do gather in colonies that spread out over large areas. These seals, including ribbon seals, harp seals, and Weddell seals, generally form pairs and males and females are about the same size.
About 12 months after mating, female seals give birth to a single
pup and female walrus to a single calf. The size
of the young depends on the species: a newborn ringed seal weighs
12 kg, and a newborn walrus 63 kg. The young grow very fast, and
quickly build up a layer of blubber because seal milk is extremely
rich in fat and protein. The blubber is important because it keeps
seals warm under the water. How long the young suckle milk from
their mothers depends on the species: hooded seals suckle for
three to five days and the pups grow from 22 to 43 kg in that
time. Sea lions, fur seals and walruses suckle their young for
one to two years. Although newborn seals don't have blubber when they
are born, they do have fur that traps air next to the skin to
give them insulation. Newborn harp seals on the Arctic ice, have
white fur that may trap more solar heat next to the skin. Most
seals lose infant fur as they develop blubber.
Conservation
status
Commercial hunting of seals in the 18th and 19th century and in the early years the 20th century played a 
large role in declining seal numbers. Elephant seals were killed for their blubber, which was boiled down to make oil. Their oil was prized as second only to that of sperm whales. Walrus were killed for their ivory tusks, their
blubber (for oil) and flesh. Fur seals were killed for their skins,
and many populations were wiped out.
Dangers for seals today include drowning after getting entangled in rubbish in the sea and in fishing nets and lines.
Click
here to find out about seals found in the Antarctic
Click
here to find out about the Australian sea-lion
Click
here to find out about threats to marine mammals from humans
If you use any part of
this, acknowledge it in your bibliography like this:
Pinninpeds
(2002).
[Online], Available: www.kidcyber.com.au
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Animals
Updated July 2007