Introduction to Seal
Seal, a meat-eating mammal found in all oceans of the world, but most abundant in Arctic and Antarctic waters. Some seals swim up rivers, and a few are found only in freshwater lakes. Probably the best-known seal species is the Californian sea lion, which is often trained to perform tricks. It is the species most often found in zoos.Seals are skillful swimmers and divers.
Some species of seals are hunted commercially—more for their blubber (fat) and pelts than for their flesh. The fur of some species is popular for fashionable wearing apparel; the hide of other species is used for leather. Oil rendered from the blubber goes mainly into soap. Seal flesh is eaten by Aleuts and was once a welcome food for seafarers. In some localities the flesh is utilized for fertilizer and animal feed. Eskimos have traditionally depended largely on seal, which they hunt with harpoons, for food, clothing, and hides for tents and boats.
Seals along with the walrus make up the taxonomic group Pinnipedia. Some authorities use the term “seal” in referring to all members of the group. For information on the walrus,
|Facts in brief about seals|
|Names: male, bull; female, cow; young, calf, pup, or whelp; group, herd or pod.|
|Gestation period: About 8 to 12 months, depending on the species.|
|Number of newborn: Usually 1, rarely 2.|
|Length of life: 40 years or more.|
|Where found: Along the coasts of most continents; a few kinds in freshwater lakes and inland seas.|
|Scientific classification: Seals make up a group of animals called the pinnipeds. Traditionally, they have been classified as a suborder of the order Carnivora, which includes such land mammals as bears, cats, and dogs. Some zoologists consider the seals a separate order, Pinnipedia. Fur seals and sea lions belong to the eared seal family, Otariidae. Earless seals make up the family Phocidae. Walruses belong to the walrus family, Odobenida. The northern elephant seal is Mirounga angustirostris, and the southern elephant seal is M. leonina. The harbor seal is Phoca vitulina. The hooded seal is Cystophora cristata, and the crabeater seal is Lobodon carcinophagus.|
Seals are divided into two families—the eared seals (the sea lions and fur seals), and the earless seals (also called true, or hair, seals). Eared seals have small, protruding earflaps on the side of the head. Earless seals have no earflaps. (All seals have internal ears.)
A seal's body tapers from the chest towards the tail, which is very short or nearly absent. The digits of a seal's four limbs are modified into flippers —the digits of the “hands” and “feet” are webbed and resemble paddles. Flippers are very useful in steering and maneuvering in water. Earless seals have fur-covered flippers; eared seals have flippers covered only with thick skin.
Seals are warm-blooded animals—that is, their body temperature remains constant regardless of the outside temperature. All seals have a layer of blubber under the skin that acts as an insulator against the cold. Sea lions, which are generally found in warmer climates than other seals, have little additional protection. Earless seals, on the other hand, have a circulatory system that limits the quantity of blood that flows through the skin and thus reduces the amount of body heat lost from the skin. The fur seals, in addition to blubber, have a two-layer covering of fur. The upper layer consists of coarse guard hairs; the dense lower layer is made up of short, fine hairs and acts as an additional insulator.
Seals have large, roundish eyes that in some species are huge in proportion to the size of the skull. The eyes have thick, spherical lenses that enable the seals to see well under water. Unlike most other mammals, seals do not have tear ducts. Thus when seals are observed on land they look as though they are crying because their tears run out of the eye onto the face. Seals have rather long whiskers around the mouth.
Adult seals weigh from about 130 pounds (60 kg) to more than 8,000 pounds (3,600 kg), depending on the species and individual. They range in length from less than 4 1/2 feet (1.4 m), for the Baikal seal, to 20 feet (6 m), for the southern elephant seal. The bulls (males) are usually larger than the cows (females), except in some species of earless seals. The lifespan of some species is up to 40 years.
In many species, the male has a thick layer of fur, resembling a mane, around the neck. Seals vary in color depending on the species, and sometimes members of the same species have different coloration. In general, they are brownish or grayish, often with various shadings, blotches, or stripes.
Pinnipeds are all big animals, but they do vary in size. In length, pinnipeds can vary from about 4 feet (1.2 meters) to about 16 feet (4.9 meters). They may weigh from about 110 pounds (65 kilograms) to about 8,800 pounds (4,000 kilograms).
Ringed seals, which look plump, are among the smallest pinnipeds. Cape (South African) fur seals are longer and heavier than many kinds of fur seals that live in other places. They are the largest fur seals.
Elephant seals are the only pinnipeds that are longer and heavier than walruses. Elephant seals are the largest pinnipeds in the world. Southern elephant seals live near Antarctica. They are even larger than Northern elephant seals, which live near the southwestern United States and Mexico.
Adult male pinnipeds are usually larger than adult females.
Seals are skillful swimmers and divers. They can swim up to 15 to 18 miles per hour (24 to 29 km/h) and are very agile in the water. The eared seals get their swimming thrust mainly from the forelimbs. The earless seals get most of their thrust from their hind limbs. Seals can dive to great depths—160 to 600 feet (50 to 180 m) is common, but some northern elephant seals have been recorded diving to depths of more than 2,000 feet (610 m). Many species are capable of remaining submerged for 20 minutes, some for more than 30 minutes.
On land, seals are rather clumsy. Eared seals, which can bring their hind limbs under their body, can stand on all fours and manage to move with a kind of gallop. Earless seals cannot move their hind limbs forward; they move on land by using their forelimbs and wriggling their body. Some seals, such as the common, or harbor, seal, spend much of their time on land; others, such as the northern fur seal, may spend up to eight months at sea. Many species spend their time out of the water exclusively on ice (rather than land).
Seals eat fish, crustaceans, squid, and occasionally, birds and other seals. They catch their food primarily with their mouths.
Most species of seals return year after year to the same area—often the place of their birth—for breeding. These breeding grounds are called rookeries. Some species travel great distances each year from their feeding grounds to their rookery. Most seals have well-defined and short breeding seasons so that all the seals of a colony come together at the same time.
All eared and some earless seals are polygamous. The mature bulls attempt to gather a harem of females, and those who succeed are called harem bulls. The size of the harem, ranging from 3 to 40 females, depends on the species and on the strength and ferocity of the bull. Except for the gray and elephant seals, the earless seals are believed to be monogamous.
In polygamous species, the mature bulls are the first to arrive on the breeding grounds, where they attempt to establish definite territories. The females, pregnant from last year's mating, arrive two weeks later. A single pup is born within one week. After the birth, mating takes place. The gestation period is 250 to 365 days. Immature bulls arrive at the rookeries a few weeks after the mature males and remain on the fringes of the colony. A young bull is not sexually mature until four years of age and does not attempt to establish a harem until five to seven years of age.
Most pups (baby seals) are precocial (born in an advanced state of development) and are able to swim soon after birth. A newborn pup is thin, though it appears to be fat because it has a thick coat of fur. The pup grows quickly and, because the mother's milk is 45 per cent fat, it soon develops a thick layer of blubber.
Earless seals make up the family Phocidae.
is found in oceans—and sometimes large rivers—of the Northern Hemisphere. Some populations inhabit freshwater lakes. Both sexes are dark gray above and lighter below. The entire body is marked with brown or gray spots. Males grow up to 6 feet (1.8 m) in length and weigh up to 550 pounds (250 kg). Females are about 12 inches (30 cm) shorter and less than half the weight.
The common seal is Phoca vitulina.
Many kinds of pinnipeds migrate long distances to find food or breeding grounds. But one seal that usually stays close to home is the harbor seal.
Harbor seals live mainly along shorelines. They can be seen along both the east and west coasts of the United States. Their favorite places are harbors.
Harbor seals usually haul out on rocks, piers, and sandbanks. Females often give birth where tides go in and out, away from boats and other dangers. Their pups can swim when they are just a few minutes old. But harbor seal pups rarely swim alone. Their mothers go with them. If the adult senses danger, she may take her pup in her mouth and dive underwater with it.
A pup might even get a ride on its mother's back while she hunts for food.
There are two species—the southern elephant seal, which is the largest of all seals, and the northern elephant seal. The name is derived from the male's trunklike proboscis, an overdeveloped nose. The southern species is found around Antarctica. The male may be up to 20 feet (6 m) long and weigh 8,000 pounds (3,600 kg). Females are smaller. Bulls are bluish-gray above and pale gray beneath. Females are brownish-gray with lighter necks and underparts. The northern elephant seal resembles the southern, except that it is smaller and has a larger proboscis. In an adult male northern elephant seal, the proboscis may extend downward for 12 inches (30 cm) or more.
By 1900, elephant seals were almost exterminated for their blubber. They have been protected by international agreements since the 1930's, and their population is increasing.
The southern elephant seal is Mirounga leonina; the northern elephant seal, M. angustirostris.The elephant seal is the largest of all seals.
An elephant seal’s nose looks like an elephant’s trunk, but it is shorter. Only male elephant seals have trunks for noses, which they use to attract female elephant seals.
Elephant seals are the biggest pinnipeds. Whales are the only sea mammals that are larger. Southern elephant seals may weigh up to 8,800 pounds (4,000 kilograms), and males may be more than 16 feet (4.9 meters) long.
Elephant seals cannot walk on all fours. They cannot rotate their hind flippers the way fur seals can. Elephant seals use their front flippers and strong stomach muscles to pull themselves forward, which makes them look like big caterpillars moving on land. Even though elephant seals cannot move very fast or far on land, they are excellent divers and swimmers.
When elephant seals molt, they lose large patches of skin and hair. Some females wallow in mud as they molt.
Elephant seals have been known to dive more than 5,000 feet (1,524 meters). That’s almost a mile!
In fact, elephant seals spend most of their time at sea. They do not need to rest very long between dives. Sometimes, they dive for more than an hour without coming up. That's a long time to dive without breathing! How do they do it?
Elephant seals store a lot of oxygen in their blood. They store more oxygen than most other kinds of pinnipeds. They use this oxygen while they are underwater. This allows them to go for a long time without breathing air.
During their dives, elephant seals look for food. Their favorite foods are deepwater fish and squid. But they also eat small sharks and octopuses.
is found in the North Atlantic. Males grow to more than 9 feet (2.7 m) and females up to 7 feet (2.1 m). Weights are up to 630 and 550 pounds (285 and 250 kg), respectively. The color varies in different individuals from dark to light gray, brown, and silver. Underparts are usually lighter and the whole body surface is marked with spots.
The gray seal is Halichoerus grypus.
is found in the Arctic and northern Atlantic oceans. Both sexes reach a length of about 6 feet (1.8 m) and a weight of about 400 pounds (180 kg). Harp seals are grayish-yellow with a broad dark band starting at the shoulders and continuing along the sides. These seals are migratory and breed on drifting pack ice. The pups were formerly killed in large numbers for their white, woolly pelts.
The harp seal is Pagophilus groenlandicus.
Newborn harp seals have silky, white coats. In fact, the pups are called whitecoats. Although fur seals are born on land in rookeries, harp seals are born on pack ice. These floating blocks of ice can be crowded and noisy.
Mothers stay with their pups for about 10 to 12 days. Then they go off to find food for themselves. They do not return to their pups.
After about two weeks, a pup’s white coat turns gray. The pup is also ready to swim now. It goes off to find food for itself. At first, the pup does not go very far. But as it gets older, it joins other young harp seals.
is usually found around Antarctica. The adult bull is up to 10 feet (3 m) long, the female as much as 2 feet (60 cm) longer. The head of the leopard seal somewhat resembles that of a reptile. Body color is dark gray on the back, shading to light gray on the underparts. The entire body is marked with spots. The leopard seal is the only seal to feed on penguins and other seabirds.
The leopard seal is Hydrurga leptonyx.
Yes, there is, and it is the leopard seal. Leopard seals resemble leopards in the spotted pattern of their fur and the way they attack their prey.
Leopard seals have a bad reputation—partly because of their appearance and partly because of their actions. A leopard seal looks fierce. It has a big head, a wide mouth, and long canine teeth. And its long, thin body makes the leopard seal look more like a lizard than a seal. Underwater, it makes long, deep, droning sounds. It's not an animal you’d want to meet!
Leopard seals live near the South Pole. They often live alone—in the water or on pack ice. Like other pinnipeds, leopard seals swim and dive for their food. But leopard seals are also able to leap out of the water and onto ice to capture and kill their prey. They have been seen killing sea birds and penguins—as well as other seals.
is one of the most abundant seals. It lives primarily in the Arctic Ocean and adjoining seas, but also in certain freshwater lakes. It averages four feet (1.2 m) in length and 140 pounds (65 kg) in weight. Ringed seals are grayish-black with light-colored oval rings above. Many are killed for skins, fur, oil, and meat.
Related species are the Baikal seal, of Lake Baikal in Siberia, and the Caspian seal, of the Caspian Sea, between Europe and Asia.
The ringed seal is Pusa hispida; the Baikal, P. sibirica; the Caspian, P. caspica.
A mother ringed seal cares for her pup in a special way. She builds her pup an ice house!
Here you see how the mother builds the ice house. She swims under the ice until she finds a place where it has cracked. Where there are cracks, there are also holes. The mother seal comes up through a hole. She then uses her sharp claws to dig in the ice and snow. She hollows out a place to give birth and to care for her pup. The ice house is warm and snug—and safe!
Ringed seal pups are small. They do not have much blubber on their bodies. To keep warm, they cuddle close to their mothers. When they get a little older, the pups may dig tunnels to other nearby ice houses.
Baikal (by KAHL) seals are special because they live in a freshwater lake instead of a saltwater sea. That lake is Lake Baikal, the deepest lake in the world. Lake Baikal, which is in Siberia, is covered with ice much of the time. In winter, the ice may be 3 feet (90 centimeters) thick!
Baikal seals feed mostly on fish in the lake. Each seal usually makes its own breathing hole in the ice. Each seal also makes its own haul-out hole. Occasionally, two or more seals may share the holes they make.
In summer, the ice breaks up. Baikal seals haul out on rocks along the shore. Baikal seals are among the few pinnipeds that sometimes give birth to twins. Newborn Baikal pups have fur that is white and woolly. As they grow up, their coats become much darker.
generally lives within sight of the Antarctic mainland. Males measure up to 10 feet (3 m), females up to 11 feet (3.4m). Both sexes weigh up to about 900 pounds (410 kg). The Weddell seal is dark gray above, lighter gray below. The entire body is marked with blotches and streaks.
The Weddell seal is Leptonychotes weddelli.
include the hooded, or bladder-nose, seal (Cystophora cristata); bearded seal (Erignathus barbatus); ribbon seal (Histriophoca fasciata); crabeater seal (Lobodon carcinophagus); Ross seal (Omnatophoca rassi); Mediterranean monk seal (Monachus monachus); Hawaiian monk seal (M. schauinslandi); and Caribbean monk seal (M. tropicalis). The Mediterranean and Hawaiian monk seals are endangered. The Caribbean monk seal is probably extinct; the last recorded sighting of one was in 1962.
A male ribbon seal has dark brown fur with white or light yellow bands around its neck, its front flippers, and its lower back. These bands look like ribbons.
A large group of these seals lives in the Bering Sea, which is part of the North Pacific Ocean. Ribbon seals like to haul out on pack ice. Pack ice is a large mass of floating ice.
Ribbon seals are speedy walkers on ice. Like many other pinnipeds, they use their front flippers for walking and their back flippers for swimming. On land, ribbon seals can move faster than a human running at top speed.
A ribbon seal may look as if it wears ribbons. But a ringed seal appears to wear rings. And it wears these rings all over its body!
Ringed seals are among the smallest pinnipeds. They live mostly in the Arctic, where there is a lot of ice. When ringed seals are breeding, they like fast ice. Fast ice is ice that is attached to land—rather than ice that is floating in the water. Nonbreeding adults like pack ice. Of course, there is a lot of water under the ice, and that is where ringed seals hunt for food.
Ringed seals have sharp claws on their front flippers. They use their claws to make breathing holes in the ice. When they stop hunting and come up for air, the seals must be very careful. A polar bear may be waiting at the hole for its next meal!
Hawaiian monk seals live in Hawaii, where the climate is warm all year. They have the same amount of blubber as seals in cooler climates. So they must try harder to cool off when they haul out.
The seals cool off by lying quietly in the shade or wet sand all day. They may lie on their dark backs with their light-colored bellies up. Their hearts beat slowly and they breathe slowly. They dive for food at night.
Hawaiian monk seals do not migrate to cooler places, but they may travel far to find food.
Long ago, there were many monk seals in Hawaii. But today, few are left.
The fur seals and sea lions make up the family Otariidae.
is found in the Galápagos Islands, along the coast of California, and in parts of Japan. Males attain a length of 7 feet (2.1 m), females 6 feet (1.8m). Weight is up to 600 pounds (270 kg) for the male, 200 pounds (90 kg) for the female. Body color is some shade of chocolate brown, and the top of the head becomes lighter with age.
The Californian sea lion is Zalophus californianus.
was formerly one of the most hunted seals. These seals are known for their seasonal migrations. They spend the winter and spring dispersed through the southern regions of the North Pacific Ocean. They breed in the Pribilof, Komandorskiye, Kuril, and Robben islands of the North Pacific. Adult bulls are about 7 feet (2.1 m) long and weigh about 600 pounds (270 kg). Females are about 5 feet (1.5 m) long and weigh up to 130 pounds (60 kg). Males have dark brown fur except for the mane, which has a grayish tinge. Females are slate gray above and reddish-gray below. Both sexes have a patch of lighter fur on the chest.
The northern fur seal is Callorhinus ursinus.Alaskan fur seals are large, eared seals of the North Pacific.
live in seas near Baja California, South America, South Africa, Australia, and Antarctica. There are eight species. One of the most numerous is the South African, or cape, fur seal. It is the largest fur seal, reaching a length of 7.5 feet (2.3 m) and a weight greater than 660 pounds (300 kg). It is commercially hunted; a subspecies, the Australian fur seal, is protected.
The South African fur seal is Artocephalus pusillus; the Australian, A. p. doriferus.
The other southern fur seals are the South American fur seal (A. australis); New Zealand fur seal (A. fosteri); Galapagos fur seal (A. galapagoensis); Antarctic fur seal (A. gazella); Philippi, or Juan Fernandez, fur seal (A. philippi); Guadalupe fur seal (A. townsendi); and Kerguelen, or subantarctic, fur seal (A. tropicalis).
A fur seal has not one, but two layers of fur that cover its body. This thick fur keeps the animal warm and dry.
Fur seals can swim very fast. They paddle with their front flippers. Fur seals stick out their heads and necks to steer. On land, fur seals use all four flippers. See how this seal is sitting. Its hind flippers are turned forward and down. When the seal walks, it uses all four flippers to do so.
Underwater, fur seals have other features that help them find food and avoid enemies. Their small ear flaps curl over their ear openings. This helps keep water out. Their large, round eyes help them see in dark water. Their nostrils close when they dive, and they hold their breath until they need to come up for air. Their whiskers probably help them find food by touch.
For a fur seal, the right time for a swim is almost always. Like all pinnipeds, fur seals spend most of their time in the water. Their body shape makes them strong swimmers and divers.
Fur seals search for their food in the water. Most of the time, they find fish and other sea animals near the surface of the water. Sometimes, they must dive to find food. Some of the dives are shallow, but others are quite deep.
Fur seals may spend days at a time in the water. They are most active during the evening, at night, and early in the morning. They sleep during the middle of the day, floating on their sides.
Fur seals spend a lot of time in the water. But sometimes they need to “haul out.” When a fur seal hauls out, it uses its front flippers to pull itself up onto land or ice.
Fur seals haul out to rest and warm up in the sun. They may also haul out to escape from enemies, such as killer whales or sharks.
There are two other important times when fur seals leave the water. They haul out at molting time. When seals molt, they shed their old fur coats and grow new ones. And they haul out to have their pups.
Fur seals come out of the water for good reasons, but getting out may not be so easy. A male Cape fur seal, also called a South African fur seal, may be more than 7 feet (2 meters) long and weigh more than 660 pounds (300 kilograms). That’s a lot of body to be dragging out of the water!
If you could see inside a fur seal’s body, here is how its bones would look.
Above the ankles, the fur seal’s four long legs are inside the seal’s body. The ankles and feet form large flippers. Each flipper has five toes. The toes are webbed, which means that they are connected by skin. The webbed feet act like paddles, helping the seals swim.
The spine, or backbone, of a fur seal is special, too. A fur seal uses its spine to make snakelike motions. These motions help propel the seal through the water.
Fur seal pups are born in the spring or summer. Mother seals usually give birth to only one pup at a time.
Newborn seal pups are more developed than human babies are at birth. Fur seal pups can walk and swim, but they wait a few weeks before they go into the water. Their eyes are open, and they can make sounds. Fine, soft fur covers their bodies. When the pups grow up, they will have fur like their parents have.
At first, a pup drinks only its mother’s rich milk. But pups grow up fast. Very soon, they are able to find their own food in the water.
Fur seal pups are born on land, in a place called a rookery. Thousands of mothers and their babies may crowd into a single rookery.
A mother Cape fur seal stays with her pup for most of the first week of its life. Five to seven days after giving birth, she goes off to sea to find food for herself. She eats and eats. It takes a lot of energy to feed a growing pup!
How does the mother find her own pup when she returns to the rookery? After she hauls out, the mother calls to her pup. The pup hears her and calls back. Each mother and pup have their own special call. This helps them to find each other in the crowded rookery.
When a mother and her pup find each other, they often rub noses. Each mother and pup also have a special smell. A mother knows that she has found the right pup by its smell.
is found throughout the North Pacific and the Arctic Ocean. It is the largest of the eared seals. Bulls are up to 11 feet (3.4 m) long and weigh up to 2,000 pounds (900 kg). Females rarely exceed 8 l/2 feet (2.6m) and a weight of about 600 pounds (270 kg). The color is variable but is usually a yellowish shade of buff. The male has a thick, muscular neck with a mane of coarse, long hairs.
The Steller's sea lion is Eumetopias jubatus.
include the Australian sea lion (Neophoca cinerea), the southern sea lion (Otaria byronia), and Hooker's sea lion (Phocarctos hookeri).
No, but sea lions do have some things in common with those big cats. That’s why lion is part of their name. Male lions have manes. So do many kinds of male sea lions. Sometimes, male sea lions even roar like lions.
Among the pinnipeds, sea lions and fur seals are close cousins. Both swim with their front flippers and can walk on all fours. Both have ear flaps that cover their ear openings. Most sea lions are bigger than fur seals, however. The coats of sea lions are not so thick, but they do have more blubber. This layer of fat under the skin keeps the sea lions warm. It also gives them energy.
Many people think sea lions are quite smart. The reason is that sea lions can learn to do many things. And they remember what they learn.
Sea lions can follow word signals and hand commands. They can also find objects underwater. Sea lions can jump through hoops and clap their flippers together.
Sea lions are most at home in oceans and seas. But you may have seen some in a zoo, a circus, or an aquarium. Perhaps you have seen a California sea lion balancing a ball on its nose and getting rewarded with a fish. California sea lions are good performers.
The U.S. Navy has been using sea lions and dolphins to find and help recover objects that are sunk deep in the ocean. Since sea lions are such great divers, they can do the work better than humans.
Sea lions are also helping scientists study whales. Whales are hard to observe because they spend almost all their time underwater. Even if scientists get into the water with whales, the animals might sense the humans. The whales might respond to the people rather than behaving as they usually do.
Whales are used to being in the water with sea lions. So scientists are training these animals to wear cameras and to videotape whales. It will be interesting to see how successful sea lions are in becoming “whale watchers.”
The commercial hunting of seals is controlled in many parts of the world by law and international treaty for purposes of conservation. Many species may not be hunted at all; others are protected except for an occasional period of culling (selective hunting). In the case of thriving species, hunting is generally confined to killing bachelor bulls, yearlings, and pups, so as not to interfere with breeding.
Pelagic sealing—the killing of seals at sea, where it is impossible to distinguish between bulls and cows—has been largely eliminated. Seals are usually hunted at their rookeries, where bachelor bulls occupy a territory separate from the harem bulls and their families. The seals are commonly clubbed or shot to death and the carcasses dressed on the spot, in order to take the blubber, the skin, or both.
Ringed seals, Caspian seals, and South African fur seals are among the most commonly hunted species today. Harp seals were killed in large numbers until 1983, when what is now the European Union banned the import of their pelts.
In the past, certain pinnipeds were in danger. Some, like the harp seal, were overhunted for their fur. Pinnipeds were also hunted for food, oil, and skins.
Seals have few natural enemies. They may fall prey to whales and sharks in the water. On ice, polar bears are their biggest threat. But, people create the biggest dangers faced by pinnipeds. People diminish their food supply. People make the waters pinnipeds swim in dangerous. So, only people can protect these animals.
Hawaiian and Mediterranean monk seals are still endangered (there are so few of them, they might become extinct). So are Northern sea lions (sometimes called Steller’s sea lions). The Caribbean monk seal has already become extinct (meaning all the animals of that kind have died).
As people became aware that entire species were becoming extinct, they passed laws to protect the animals, including pinnipeds. Over time, these laws have helped more pinnipeds to survive.
The earliest known instance of organized sealing occurred along the Barbary Coast of Africa, where the Mediterranean monk seal was hunted for its skin in the 15th century. By the end of the 18th century, explorers had discovered most of the major seal herds in the world, and sealing, for blubber and skins, grew into an important industry. In the early 19th century the slaughter reached such proportions that one species, the Philippi fur seal, became extinct. When seals had grown so scarce that the industry itself almost died, protective measures began to be taken.
In 1911 an international treaty outlawed pelagic sealing of northern fur seals, which had almost become extinct. Large numbers of northern fur seals continued to be hunted on the Pribilof Islands until 1985. Since then, they have been hunted only by the Aleuts, for their own food supply.
Other species, including the elephant seals and some southern fur seals, have also received protection from international treaties. In the United States, the Marine Mammal Protection Act of 1972 prohibited most hunting of seals.
When a pinniped is hauled out, it’s easy for scientists to observe its behavior. Scientists have watched pinnipeds haul out to rest and warm themselves. Scientists have watched pinnipeds give birth, care for their young, and molt. Scientists have even observed pinnipeds escaping from enemies.
But there is still a lot that scientists do not know about pinnipeds. It’s hard to observe these animals when they are not hauled out. So we do not know much about their habits at sea.
Scientists have, however, found ways to track these animals. They have attached time-depth recorders and radio transmitters to some seals. These tell where the seals swim and how deep they dive. By using these devices with satellites, scientists hope to learn even more about pinnipeds at sea.