TRUE SEALS: Phocidae

PHYSICAL CHARACTERISTICS

True seals have a tapered shape, with short hair covering their body. Underneath the thick skin are 5 to 6 inches (11 to 13 centimeters) of blubber, or fat, that conserves body heat and stores food energy. They are also called earless seals, because they do not have external ears. The ears are just tiny openings on each side of the rounded head. Unlike eared seals, true seals cannot rotate their back flippers for walking. For movement on land, they crawl on their undersides, with the rear end and front flippers pushing the body along. In water, the webbed back flippers act as paddles, while the front flippers are used for steering and balance.

GEOGRAPHIC RANGE

True seals inhabit all oceans, except the Indian Ocean. Some species live in inland lakes in Siberia, Russia, and Finland.

HABITAT

True seals forage, search for food, at sea, but haul out (get out of the water) to land to breed, molt, or shed fur, and rest. They prefer ice floes, large sheets of floating ice, or fast ice, ice attached to a land mass. They also inhabit sand, cobble, and boulder beaches, as well as caves and rocky outcrops.

DIET

True seals eat mostly fish. They also feed on krill, squid, octopuses, and other seals.

BEHAVIOR AND REPRODUCTION

True seals congregate on land or ice to breed and molt. The males and females of some species migrate, travel, separately from breeding to foraging areas. Others species do not migrate. Only the male elephant seals and gray seals gather groups of females during the breeding season. In some species, cows, females, nurse their young for just a few days, fattening up the pup, and then letting it fend for itself.

TRUE SEALS AND PEOPLE

Native people have always depended on seals for food, oil, and fur, taking only what they need for their local populations. Commercial sealers, on the other hand, have overhunted some species.

DEEP DIVERS

Northern elephant seals are able to dive to deep ocean depths because of certain bodily adaptations. They reduce oxygen use in the muscles, tissues, and other organs and redirect that oxygen supply to the important organs, the heart and brain. Human divers may suffer decompression sickness, or the "bends," when rising to the water surface because of nitrogen bubbles trapped in the blood. Seals collapse their lungs when diving, ridding the lungs of any air, and therefore avoid the bends.

CONSERVATION STATUS

Three true seals are considered threatened species due mainly to habitat loss or degradation. The Caribbean and Hawaiian monk seals are listed as Endangered, facing a very high risk of extinction, by the U.S. Fish and Wildlife Service. The World Conservation Union (IUCN) lists the Mediterranean monk seal as Critically Endangered, facing an extremely high risk of extinction in the wild, the Hawaiian monk seal as Endangered, and the Caspian seal as Vulnerable, facing a high risk of extinction in the wild.

HARP SEAL (Pagophilus groenlandicus:): SPECIES ACCOUNTS

Physical characteristics: Harp seals got their name from the harp pattern on their back. Adult males and females are light silvery gray with a black face. In males, the harp marking is black. In females, the marking may be broken into smaller patterns. Each seal measures about 5.6 feet (1.7 meters). Males weigh about 297 pounds (135 kilograms) and females about 240 pounds (109 kilograms). Harp seals have a thick layer of blubber that protects them from the cold and stores food energy. The front flippers have strong, sharp claws for hauling out of the water and moving across ice. The back flippers function as oars for swimming but cannot be turned forward for walking.

Geographic range: Harp seals live in the Arctic and the North Atlantic Oceans. They breed off the coast of northeastern Canada, off the east coast of Greenland, and in the White Sea off the northwestern coast of Russia.

Habitat: When not foraging or migrating, harp seals live on ice floes in the open sea. They breed and molt on offshore pack ice. They forage, search for food, under the ice or in open water.

Diet: Harp seals feed on a variety of fish, including capelin, cod, and herring. They also eat shrimp, crabs, and squid.

Behavior and reproduction: Harp seals feed and travel in large groups. They are playful, porpoising or making arcing leaps over water, like dolphins and sea lions. They are excellent divers, able to stay underwater for thirty minutes at a time. They vocalize underwater and on land.

Females gather on pack ice in late winter to give birth to single pups and nurse for about two weeks. Soon after, each cow mates in the water, then returns to sea, leaving her pup permanently. Within those two weeks, the pup grows from about 24 pounds (11 kilograms) to about 80 pounds (36 kilograms). After another two weeks, it sheds its white downy coat, replacing it with a shorter silvery gray coat. They learn to swim and find their own food. After mating, the adult males leave to feed at sea, hauling up on shore to molt for about a month before continuing their northward journey.

Harp seals and people: In the 1970s and 1980s, pressure from conservationists caused the closing of American and European markets for seal products. The seal trade has continued, with new markets in Russia, China, Poland, and Ukraine bringing in millions of dollars for the fur alone. In addition, seal genitals are marketed to Asian markets as aphrodisiacs (aff-roh-DEE-zee-acks), substances that are supposed to increase sexual desire. In 2004, the Canadian government announced an additional quota of 100,000 seals available for hunting for an annual total of 350,000 seals.

Conservation status: Harp seals are not a threatened species. ∎

NORTHERN ELEPHANT SEAL (Mirounga angustirostris): SPECIES ACCOUNTS

Physical characteristics: The northern elephant seal got its name from the male's nose, which resembles an elephant's trunk. Males weigh three or four times as much as females, averaging 3,750 pounds (1,704 kilograms) and measuring about 13.2 feet (4 meters). Females are about 1,122 pounds (510 kilograms) and 10.6 feet (3.2 meters) long. Males are dark brown. The thickened, pinkish throat and neck protect them against sharp teeth during fights at the rookeries, breeding grounds. The nose can be inflated to give a bigger appearance and to make loud noises for threat displays. Females are light to chocolate brown.

Geographic range: Northern elephant seals forage in the North Pacific Ocean and breed off the coast of northern California to Baja, Mexico.

Habitat: Northern elephant seals forage at sea as far north as the Gulf of Alaska and the Aleutian Islands. They breed on sandy, cobble, and pebble beaches.

Diet: Northern elephant seals feed on deep-sea fish, such as Pacific whiting, ratfish, and shark, as well as squid, octopuses, crabs, and eels.

Behavior and reproduction: Northern elephant seals spend up to 90 percent of their time underwater, diving for twenty to thirty minutes, and then coming up for air for about three minutes. They have been recorded diving as deep as 1 mile (1.6 kilometers). Average diving depths range from 1,650 to 2,300 feet (about 500 to 700 meters). In winter, bulls haul out to establish breeding territories. Pregnant cows go ashore a month later, giving birth to single pups. After nursing for about a month, females mate with the territorial bull and with other subordinate males. She then goes back to the sea, leaving the pup to fend for itself. Both sexes fast, go without food, while on land, up to three months for the males. After foraging at sea, each migrates back to the breeding grounds to molt. Each year, seals shed both old skin and hair in what is called catastrophic molt. Northern elephant seals migrate a long distance twice a year, to breed and then to molt, traveling over 6,000 miles (10,000 kilometers) each way.

Northern elephant seals and people: Northern elephant seals were thought extinct by the late 1800s due to overharvesting for its blubber, primarily used in lamp oil. Since the early 1900s, when the seals appeared in Mexico and California, the U.S. government and Mexican government have taken steps to protect them.

Conservation status: Northern elephant seals are not a threatened species. ∎

HAWAIIAN MONK SEAL (Monachus schauinslandi): SPECIES ACCOUNTS

Physical characteristics: Adult Hawaiian monk seals have short, silvery gray coats, which turn lighter on their undersides. As a seal ages, its coat turns a deep brown with each molt. Females, at about 7.5 feet (2.3 meters) and 528 pounds (270 kilograms), are larger than males. Males measure about 6.9 feet (2.1 meters) long and weigh 385 pounds (175 kilograms).

Geographic range: Hawaiian monk seals are found in the United States.

Habitat: Hawaiian monk seals inhabit the Pacific Ocean waters surrounding the northwestern Hawaiian islands. They breed, rest, and molt on coral reef islands. A small number are found on the main

Hawaiian Islands. Cows choose breeding areas with a coral shelf that affords protection from the sun and sharks.

Diet: Hawaiian monk seals feed on deep-water fish and other fish found in the coral reefs. They also eat squid, octopuses, and lobsters.

Behavior and reproduction: Hawaiian monk seals are solitary, living alone, except during the breeding season. Females give birth to a single pup that they nurse for four to six weeks. A cow sometimes nurses another cow's pup. Females mate soon after they leave their pups, typically in the water. Bulls are believed to have several partners. In areas where males outnumber females, mobbing occurs, in which a group of adult males attempt to mate at once with an adult or an immature female, sometimes fatally injuring that individual.

These seals are active at night, sleeping during the heat of day. They do not migrate, but may spend many days foraging at sea before going ashore to sleep. They do not tolerant humans. When disturbed, they either do not go ashore to breed or give birth in a less preferred site. Pups usually do not survive under these conditions.

Hawaiian monk seals and people: Hawaiian monk seals have recently inhabited the main Hawaiian islands. Since they are listed as Endangered and, therefore, legally protected, their appearance on tourist beaches has prompted restrictions or closure that may turn people against them.

Conservation status: The U.S. Fish and Wildlife Service and IUCN lists the Hawaiian monk seal as Endangered due to habitat loss to human expansion, lack of young females for mating, male mobbing of females, reduced prey, and entanglement in ocean debris and commercial fishing gear. ∎

FOR MORE INFORMATION

Books:

Bonner, Nigel. Seals and Sea Lions of the World. New York: Facts on File, Inc., 1994.

Cossi, Olga. Harp Seals. Minneapolis: Carolrhoda Books, Inc., 1991.

Grace, Eric S. Sierra Club Wildlife Library: Seals. Boston: Little, Brown and Company, 1991.

Le Boeuf, Burney J., and Richard M. Laws, eds. Elephant Seals: Population Ecology, Behavior, and Physiology. Berkeley, CA: University of California Press, 1994.

Patent, Dorothy Hinshaw. Seals, Sea Lions and Walruses. New York: Holiday House, 1990.

Reeves, Randall R., Brent S. Stewart, Phillip J. Clapham, and James A. Powell. Guide to Marine Mammals of the World. New York: Alfred A. Knopf, 2002.

Periodicals:

Bruemmer, Fred. "Five Days with Fat Hoods." International Wildlife (January/Febrary 1999). Online at http://www.nwf.org/internationalwildlife/1998/hoodseal.html (accessed on July 7, 2004).

Kovacs, Kit. "Bearded Seals: Going with the Floe." National Geographic (March 1997): 124–137.

Tennesen, Michael. "Testing the Depths of Life." National Wildlife (Feb/Mar 1999). Online at http://nwf.org/nationalwildlife/article.cfm?articleId=187&issueid=67 (accessed on July 7, 2004).

Williams, Terrie M. "Sunbathing Seals of Antarctica : The Puzzle Is How Do They Keep Cool? (Weddell Seals)." Natural History (October 2003): 50–56.

Web sites:

"The Hawaiian Monk Seal." Pacific Whale Foundation. http://www.pacificwhale.org/childrens/fsmonkseal.html (accessed on July 7, 2004).

"Hawaiian Monk Seal" Seal Conservation Society. http://www.pinnipeds.org/species/hawaimnk.htm (accessed on July 7, 2004.)

"Pagophilic Seals: Fast Facts." Pagophilus.org: Science and Conservation of Ice Loving Seals. http://www.pagophilus.org/index.html (accessed on July 7, 2004).

"Steller Sea Lion Biology." National Marine Mammal Laboratory. http://nmml.afsc.noaa.gov/AlaskaEcosystems/sslhome/StellerDescription.html (accessed on July 7, 2004).