Photograph by Yva Momatiuk and John Eastcott National Geographic November 2008
The name "elephant seal" actually describes two different but related species of beast: northern elephant seals, Mirounga angustirostris, and southern elephant seals, Mirounga leonina. Northern elephant seals are smaller than their southern cousins and range from the Aleutian Islands along the Pacific Coast of North America to as far south as Baja California in Mexico. Southern elephant seals stick to the cold waters off the coast of Antarctica, with populations based at many spots surrounding the continent. Key breeding populations are found off South America on Peninsula Valdes, South Georgia, and South Shetland; off the tip of South Africa at Marion Island; in the southern Indian Ocean on the Kerguélen Islands; and at Australia's Macquarie Island. In the 1880s northern elephant seals were nearly driven extinct due to harvesting for blubber, and southern elephant seal numbers also declined. Since the beginning of the 20th century, both populations have rebounded.
Elephant seals are pinnipeds ("fin-feet") from the family Phocidae, called the true seals. These seals share the following characteristics: no external ears, hind flippers that are used for propulsion when swimming but can't be brought underneath the body to help "walk"on land, thinner fur, and a thicker, insulating blubber layer. Their sexual dimorphism is great, meaning that males and females are very different sizes. Males are regularly about five times as large as females and in extreme cases can weigh up to ten times more. Male southern elephant seals are the largest pinnipeds in the world, larger even than walrus.
The species' name comes from the male elephant seal's prominent nose, which resembles a short trunk. (Females don't have a trunk.) This proboscis is made of erectile tissue and can be raised for display during mating season. Though smaller than the southern elephant seal, the northern elephant seal has a longer trunk.
During the year, elephant seals spend most of their time foraging in the open ocean. They eat a lot of squid, but have few predators (though great white sharks and killer whales have been known to eat them). Much of their time underwater is spent diving deep and then drifting upward slowly—they can stay underwater for up to two hours (though about 30 minutes is more typical) and need only a few minutes at the surface to breathe. Females tend to dive deeper than males. Twice a year all elephant seals haul out onto land for one month to a few months—in the early spring to bear the previous year's young and to mate, and in the fall to shed their skin and fur during their annual molt.
Casey, Susan. "Shore Leave." National Geographic (November 2008), 124-135.
Perrin, William F., Bernd Wursig, and J. G. M. Thewissen, eds. Encyclopedia of Marine Mammals. Academic Press, 2002.
Reijnders, Peter, et al (International Union for the Conservation of Nature Seal Specialist Group). Seals, Fur Seals, Sea Lions, and Walrus. IUCN, 1993.
Riedman, Marianne. The Pinnipeds: Seals, Sea Lions, and Walruses. University of California Press, 1990.
Sanvito, Simona, Filippo Galimberti, and Edward H. Miller. "Having a Big Nose: Structure, Ontogeny, and Function of the Elephant Seal Proboscis." Canadian Journal of Zoology (2007), 207-220.
Southern Elephant Seals as Oceanographic Samplers. Sea Mammal Research Unit University of St. Andrews, Scotland.
Southern Elephant Seal. University of Michigan Museum of Zoology Animal Diversity Web.
Northern Elephant Seal. University of Michigan Museum of Zoology Animal Diversity Web.
A collaborative program among elephant seal researchers from many spots surrounding Antarctica, the SEaOS program is the most ambitious southern elephant seal tracking program yet. Radio tags track the seals' movements and beam the results to satellites as packaged data almost in real time, and the information is then transmitted to researchers. Glued onto the seals' backs, the tags don't bother the seal—if a tag doesn't fall off in the normal course of the seal's movements (which usually happens within a few months), it will be lost when the seal goes through its annual molt (it loses skin as well as fur). Though a recovered tag can provide some additional information to scientists, the bulk of the data transmission is done by satellite, so tag retrieval isn't crucial to the program.
The program has gathered detailed information on the migrations of southern elephant seals, including how deep they dive, how long they spend at each depth, how far they travel, and where. An additional benefit: The seals provide a sampling of oceanographic data from areas of the world that are otherwise difficult to reach. Ice and extreme weather hamper research vessels in the oceans around Antarctica, but the seals are there year-round. Their radio tags test salinity and temperature, giving information on currents created by oceanic “fronts”—places where two different powerful streams of water, such as the sub-Antarctic polar current and the Antarctic circumpolar current, converge.
"Animals as Antarctic Explorers." Southern Elephant Seals as Oceanographic Samplers. University of St. Andrews, Scotland.
"Technology: Techniques, Tags, and Visualization. Southern Elephant Seals as Oceanographic Samplers." University of St. Andrews, Scotland.
In addition to hosting hundreds of thousands of southern elephant seals every year during the mating and molting seasons, South Georgia Island, perched in the South Atlantic Ocean a thousand miles due east of the southern tip of South America, is a haven for many other types of wildlife. Its rocky, icy profile is dotted by sandy inlets that are often covered with thousands of southern fur seals, king penguins, gentoo penguins, macaroni penguins, and even Weddell seals (only a small rookery, as they're usually found only in Antarctica). A herd of reindeer introduced by early whalers for dinner-on-the-hoof has created some problems for indigenous species but is currently being allowed to stay. Though stowaway rats have hurt South Georgia seabird populations, nearby islands (where rats are not yet a problem) are inhabited by tens of thousands of breeding birds, including wandering, grey-headed, black-browed, and light-mantled sooty albatrosses as well as giant petrels and sheathbills. Offshore, right whales patrol the seas.
South Georgia and the South Sandwich Islands are a British overseas territory, and the British Antarctic Survey has established two research stations at South Georgia to monitor wildlife and climate conditions and to evaluate possible fisheries.
Last updated: October 8, 2008