EARED SEALS, FUR SEALS, AND SEA LIONS: Otariidae

PHYSICAL CHARACTERISTICS

Otariids, eared seals, have streamlined, smooth, bodies that allow them to move easily through water. A layer of blubber, or fat, provides insulation. The dog-like head has small external flaps for ears. Long whiskers are sensors for finding food and alerting against predators. Flippers can be turned forward for walking on land. In water, the front flippers function as oars, while the back flippers steer and provide balance. Males are two to four times larger than females.

GEOGRAPHIC RANGE

Otariids haul out on land near the waters they inhabit, including the United States, Canada, Mexico, Argentina, Chile, Ecuador, Peru, Japan, Australia, and New Zealand.

HABITAT

When breeding or molting, shedding fur, otariids gather on rocky coastlines, sandy and gravel beaches, and caves. They also breed in mainland areas in Africa, Argentina, and Peru.

DIET

Otariids feed on krill, a small shrimp-like animal, fish, crustaceans like shrimps, crabs, and lobsters, mollusks such as clams, mussels, squid, and octopuses, and penguins. A small fur seal weighing 110 pounds (50 kilograms) consumes about 4 to 5 pounds (1.8 to 2.3 kilograms) of food per feeding.

BEHAVIOR AND REPRODUCTION

Otariids are active both day and night. Expert divers, they swim to the deepest parts of the ocean floor to forage, find food. They breed annually, except for the Australian sea lion that breeds every seventeen-and-a-half months. Some species migrate far to rookeries, breeding colonies. Females give birth to one pup a year.

OTARIIDS AND PEOPLE

In the nineteenth century, fur seals were hunted for their fur, meat, and blubber. Today fishermen consider seals as competitors for fish. Seals' body parts may be used as aphrodisiacs, believed to increase sexual desire, or ornaments. Seals may be threatened by pollution caused by humans.

CONSERVATION STATUS

The World Conservation Union (IUCN) and the United States classify the Steller sea lion as Endangered, facing an extremely high risk of extinction in the wild. They are at risk due to extensive commercial fishing of pollock, its major prey fish, human pollution, accidental tangling in commercial fishing gear, and hunting by humans.

ADJUSTABLE EYES

An eared seal's eyes are adapted for seeing in hazy seawater and bright sunlight. Underwater, the pupil, or opening at the front of the eye, expands to let in as much light as possible. In addition, a mirror-like layer behind the eyes reflects light back to the retina, increasing the amount of light entering the eyes. Out of the water, the pupil adjusts to the bright sunlight by narrowing into a tiny pinhole.

The IUCN lists many otariids as Vulnerable, facing a high risk of extinction in the wild. The Galápagos fur seal is vulnerable due to parasites and predators. The Juan Fernández fur seal is threatened by a limited population as a result of inbreeding. Guadalupe fur seals are vulnerable because of excessive harvesting. Northern fur seals are endangered by habitat loss or degradation due to human activities. Hooker's sea lions are at risk due to accidental entanglement in fishing gear and human hunting. Finally the Galápagos sea lion is vulnerable as a result of El Niño events, illegal hunting, and tangling in fishing gear.

ANTARCTIC FUR SEAL (Arctocephalus gazella:): SPECIES ACCOUNTS

Physical characteristics: Antarctic fur seals have a thick waterproof underfur and an overcoat of long guard hairs. Bulls, adult males, are dark brown or charcoal-gray. A long mane of hair protects bulls when fighting over breeding territories. Bulls measure about 6 feet 7 inches (2 meters) long and weigh up to 440 pounds (200 kilograms). Adult females, cows, are smaller in size, about 4 feet 5 inches (1.4 meters) long and weigh up to 110 pounds (50 kilograms). They are gray, with cream-colored throat and chest.

Geographic range: Antarctic fur seals live in the Southern Ocean surrounding Antarctica. They breed on the islands south of, or close to, the Antarctic polar front. About 95 percent breed on South Georgia in the South Atlantic Ocean.

Habitat: Antarctic fur seals live in the open seas and congregate on land to breed, molt, and rest.

Diet: Antarctic fur seals are the only otariids that feed mainly on krill. They sometimes consume fish, squid, and birds.

Behavior and reproduction: Antarctic fur seals are solitary, alone, at sea, usually foraging at night. Adult and subadult males congregate on land to molt. Cows may assemble in herds but do not socialize. Growing seals stay at sea for several years, only returning to their birthplaces to mate for the first time.

In late October, bulls arrive at rookeries to claim territories. They quarrel, sometimes biting one another. Males fast, go without food, for as long as two months while protecting their territory. In November, cows arrive, choose a bull's territory, and give birth to a single pup conceived the previous year. A bull has an average of eleven to sixteen cows in his territory. At birth, the pup vocalizes with its mother. After nursing for a week to ten days, the cow mates with the territorial bull. The female then feeds at sea for up to six days. A returning mother calls out to her pup who answers back. After smelling the pup to make sure it is hers, and then nurses for three or more days. The periodic foraging and nursing lasts about four months. In April, all seals leave for the sea, each going its own way.

Antarctic fur seals and people: Once hunted almost to extinction for their fur, meat, and blubber, these seals are currently protected by international agreements and by the islands where they breed.

Conservation status: The Antarctic fur seal is not a threatened species. ∎

CALIFORNIA SEA LION (Zalophus californianus): SPECIES ACCOUNTS

Physical characteristics: California sea lions have a torpedo-like body, with flippers for swimming and moving on land. Males have brown or black fur, a bulky upper body, and a thick mane over the shoulders. A crest, or a distinctive bump on the forehead, is topped with blonde or light brown hair. They weigh as much as 772 pounds (350 kilograms). Females are much lighter, weighing up to 220 pounds (100 kilograms), and are tan in color.

Geographic range: California sea lions live in the Pacific Ocean along central Mexico to southern California. In between breeding seasons, males migrate, travel, to feeding sites off Oregon, Washington, and British Columbia, Canada.

Habitat: California sea lions breed on sandy, gravel, or rocky beaches.

Diet: California sea lions are opportunistic feeders, eating whatever is available. They feed mainly on squid and octopuses, but also consume fish, including anchovies, salmon, rockfish, and small sharks. They eat at all hours of the day. They typically swallow small prey whole in water but take bigger prey to land to shake them into small pieces. Males prey on northern fur seal pups and small true seals.

Behavior and reproduction: California sea lions are active the whole day. They are the fastest marine carnivore and can swim up to 25 miles (40 kilometers) per hour. They often swim in groups, covering large distances by porpoising, leaping over water. They also rest together on the water surface in a horizontal position called rafting.

Breeding season lasts from May through July. Bulls wait for the pregnant cows to come ashore before establishing territories. After giving birth to one pup, mothers nurse their young, then forage at sea, sometimes taking the newborn with them. Three or four weeks later, mating occurs in the water. Mothers recognize their pup by sound and smell. A pup may nurse for a whole year at the rookery. The males leave for the ocean soon after breeding.

California sea lions and people: California sea lions are most familiar as talented performers in marine parks and circuses. Some fishermen consider them pests because they steal fish from nets. Sea lions have been trained by the U.S. Navy to detect suspicious swimmers and divers near military ships and ports because they have excellent underwater directional hearing and low-light vision and are able to make repeated deep dives. A sea lion can approach an intruder without being heard. Using its flippers, it will clamp a handcuffs-like device carried in its mouth onto the person's leg, allowing sailors to apprehend the suspect. The U.S. Navy has normally relied on sea lions to recover practice mines undersea.

Conservation status: The California sea lion is not a threatened species. ∎

GALÁPAGOS SEA LION (Zalophus wollebaeki): SPECIES ACCOUNTS

Physical characteristics: Male Galápagos sea lions are dark brown to black, weigh up to 550 pounds (250 kilograms), and have a bump on the forehead. Females are lighter, weighing as much as 176 pounds (80 kilograms) and are tan or blonde in color.

Geographic range: Galápagos sea lions inhabit the Galápagos Islands, a group of islands considered a province of Ecuador.

Habitat: Galápagos sea lions favor gently sloping sandy and rocky beaches for breeding.

Diet: Galápagos sea lions feed on squid and fish, including sardines, anchovies, mackerel, and rockfish in the upwelling waters, nutrient-rich waters rising from the ocean depths, along the coasts. During El Niño events, when fish populations either die or migrate, sea lions dive down deeper into the ocean to feed on lantern fish.

Behavior and reproduction: Galápagos sea lions stay on the islands year round. During the day, they forage in waters close to the islands. The breeding season is long, lasting from May to January. The cow nurses her pup for about a week, then feeds at sea, returning periodically to nurse. Three weeks after giving birth, cows are ready to mate. A bull may have as many as thirty cows in his territory. Some cows ignore boundaries, seeking males in other territories. Mating occurs in shallow water or on land. Bulls may help guard pups from sharks by a warning call or by moving them away from the water. Pups nurse for up to a year or until a sibling is born. Some cows nurse both the yearling and the newborn for another year.

Galápagos sea lions and people: Galápagos sea lions are popular tourist attractions on the islands. They are illegally hunted for their teeth for adornment, and the male genitals are believed to be aphrodisiacs, items that intensify or arouse sexual desires, in some Asian cultures.

Conservation status: The IUCN lists the Galápagos sea lion as Vulnerable due to El Niño events, tangling in fishing gear, and illegal hunting for body parts. ∎

FOR MORE INFORMATION

Books:

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

DuTemple, Leslie A. Seals and Sea Lions. San Diego, CA: Lucent Books, Inc., 1999.

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

Jackson, Michael H. Galápagos: A Natural History Guide. Calgary, Canada: The University of Calgary Press, 1985.

Miller, David. Seals & Sea Lions. Stillwater, MN: Voyageur Press, 1998.

Nowak, Ronald M. "California Sea Lion." Walker's Mammals of the World Online. 5.1 Baltimore: Johns Hopkins University Press, 1997. http://www.press.jhu.edu/books/walkers_mammals_of_the_world/pinnipedia/pinnipedia.otariidae.zalophus.html (accessed on July 7, 2004).

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:

Holmes, Bob. "Exploring the Sensory Lives of Sea Lions." Ranger Rick (June 2000): 2.

Momatiuk, Yva, and John Eastcott. "The Art of Bullying (Behavior of Northern Fur Seals)." National Wildlife (August–September 1999): 50–56.

Nelson, Roxanne. "The Blubber Bunch at Pier 39." Ranger Rick (November 1996): 14–16.

Web sites:

Bruemmer, Fred. "Comeback on a Castaway's Island." National Wildlife Federation. http://www.nwf.org/internationalwildlife/2001/seal.html (accessed on July 7, 2004).

"Golden Seals of the Skeleton Coast: Life amid the Wrecks." Public Broadcasting Service (PBS) Nature. http://www.pbs.org/wnet/nature/goldenseals/index.html (accessed on July 7, 2004).

Murphy, Verity. "Let Slip the Sea Lions of War." BBC News Online. http://news.bbc.co.uk/1/hi/world/middle_east/2839155.stm (accessed on July 7, 2004).

"Pinniped Species Information Page." Seal Conservation Society. http://www.pinnipeds.org/species/species.htm (accessed on July 7, 2004).

"Steller Sea Lion Biology." North Pacific Universities Marine Mammal Research Consortium. http://www.marinemammal.org/steller_sea_lion/fastfacts.html (accessed on July 7, 2004).