Seals

The fin-footed animals

Class: Mammalia (mammal)
Order: Pinnipedia
Family: True seals or earless seals (Phocidae) Sea-lions & fur seals or eared seals (Otariidae) Walrus (Odobenidae)

Seals have a slick, streamlined, torpedo-shaped body which makes them among the world's best divers. Millions of years of adapting to the sea modified their 4 limbs into flippers. It is these 4 flippers that give them the scientific name, pinnipedia, or 'fin-footed animals'.

Lightweights and heavyweights
The various seal species differ in size and weight. The smallest seal is the ringed seal of the Arctic, which is about 1.5 metres long and weighs up to 90 kg. The largest earless seal is the southern elephant seal, which weighs over 3,000 kg and can grow up to 6 m long. Sea lions are the biggest of the eared seals.

Male seals are generally much larger than the females. Seals have small heads with short noses and slit-like nostrils which can close under water. Seals can see and hear well but have a poor sense of smell. Most pinnipids have a covering of short hair which they shed every year.

Their bodies are padded with fatty blubber that acts as an energy store and provides insulation against the cold.

Fabulous swimmers
Seals spend most of their lives in water. The hind body is strong and muscular for swimming. Seals are so well adapted for diving that when they plunge, the heart rate drops from 50-100 beats per minute to 10 or less.

Seals come to land or ice to mate, give birth and to moult. Whilst they are usually solitary swimmers they gather into large groups on land.

Not land lovers
Eared seals are more agile on land than earless seals because they can turn their hind flippers forward. This lifts their body off the ground and helps them move forward quickly. Other seals pull themselves along or wriggle about when on land. For example, although they are swift and powerful swimmers, Southern Elephant seals are cumbersome on land, having difficulty lifting their huge bodies off the ground as they haul themselves on and off the beach.

Seal habitat
Seals are found along most coasts and cold waters but their biggest numbers are in the Arctic and Antarctic waters. The Southern elephant seal, lives in Antarctica and the sub-Antarctic waters off South America.

Monk seals are endangered species of earless seals which live in tropical and sub-tropical coastal waters. The largest colonies have occurred on the Atlantic coast of Northwest Africa. The Baikal seal is found in Lake Baikal in Russia and is the only freshwater seal.

Favourite foods
An adult grey seal usually eats about 5 kg of food per day, mainly fish. The fierce leopard seal also kills the pups of other kinds of seal, while one kind of sea-lion occasionally eats penguins. Walruses enjoy eating molluscs such as oysters, echinoderms such as starfish, and crustaceans such as shrimps.

Nurturing the young
Some seals give birth to their young (called pups) on land or ice floes. Some species of seals gather together in large numbers during the breeding season. These groups are called colonies or rookeries. Islands are popular breeding grounds because there are fewer predators around to kill the young.

A grey seal male (bull) will establish a territory in the breeding colony and in the sea nearby. Up to 70,000 grey seals can gather together in a single breeding colony! Grey seals give birth to their young in the autumn or winter.

Usually, only one pup is born. Grey seals, like other earless seals, suckle their pups for just a short time. When she is suckling the pup, the mother does not feed, drawing on her reserves of fatty blubber to produce milk. Pups, however, grow rapidly and are ready to find their own food after about 2 weeks.

A bull mates with several females (cows) soon after they have given birth. Mating happens in the sea or on land. It takes 10 months to 1 year before the new pups are born.


Conservation concern
Human greed has led to the decline of many seal populations. In the past, millions of seals were killed for their valuable meat, blubber, and hides. Walruses are killed for their ivory tusks. Some kinds of seals are hunted for the pups' fluffy white coats. In some countries, seals are still killed in large numbers because fishermen blame them for the decline in fish.

Some seal species are under threat. The Mediterranean monk seal is listed as critically endangered by IUCN, with a total population thought to be as low as 300-500.