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By the time the southern elephant seals reach Año Nuevo State Reserve, California, where they will give birth to their pups between January and February, they will have traveled nearly 9,000 miles and are at the end of the migration route.  Most are carrying satellite tags on their heads for scientific documentation, which will be removed upon arrival if it has not already fallen off due to the molting process last spring—a project which began last 1983—after ten months spent at sea. The data received is massive after that long of a period in the waters:

•    The tags use light level to determine location
•    The tags use digital electronics to gather physiological data
•    The tags use an acoustic data logger
•    The tags provide oven temperature profiles

Even though the gathered data answers many questions, the migratory routes of colonies from the Guadalupe, San Miguel, Año Nuevo, and San Nicolas bring up many question still left unanswered. Some involved whether each colony of seals migrates to different ocean places. A lot of these questions involve that fact weanling elephant seals go out to sea, with only 50% surviving. The data being received now my show what will be happening once climate change develops to the point their migratory routes will be influenced by massive amounts of melting ice.

MIGRATORY ROUTES DIFFERENT FOR BULLS

In a recent study, the Mirounga leonine male southern elephant seals were studied migrating from King George Island in relation to sea ice coverage.  In the study, fourteen males were fitted with satellite linked transmitters after the animals finished with their annual molting at Stranger Point, King George Island from March to May 2000. A 12-month tracking was held, with daily data derived from the "Special Sensor Microwave/Image of the Defense Meteorological Satellite Program".

In May of 2000, the bulls moved along the shelf margin east of the Antarctic Peninsula. In an area of increasing prey availability of organic material caused by an upwelling, the males concentrated their foraging for food close to the northern sill of the Filchner Trough. By August of the same year, they bulls returned northwards to their King George Island breeding sites.  What was found was the bulls had a different migratory route than the females and the weaned pups, whose previously tracing study showed they moved westward from King George Island into the Pacific sector of the Antarctic Ocean. 

During non-breeding seasons, the southern elephant seals can be found throughout the southern oceans. But once the breeding season begins, the population will split into three divisions north of Antarctic's pack ice—South Georgia, Macquarie Island, and Kerguelen Island. During the breeding season, the seals will remain on the beaches and rocky terrain, and sometimes on ice and snow, where they survive on the fat they have accumulated.

DECLINE OF PUPS AT SEA WHEN MIGRATING

The southern elephant seal population began declining by 50% from 1959 to 1985, continuing its decline about 1.7% annually since then. This is thought to be due to the pups and juvenile mortality loss when at sea, owing to the changes in availability of prey to keep them sustained during the long journeys—with some rumors stating the large fisheries are competing with the seals for fish in the area. The main foraging area is Antarctica waters, with the seals diving deep dives to hunt for fish, squid, ascidians and crustaceans as much as 90% of the time.

Every August, the seals return from the long ocean trips to their breeding grounds to not only mate but give birth, with the males arriving first. The females give birth to one pup, anywhere from two to five days upon their arrival. For a period of 23 days, the pups are nursed and cared for, with the females leaving the pups to fend for themselves once they are weaned. The females then return to the sea to hunt, while the pups basically are on their own by teaching themselves to swim and hunt for a period of four to six weeks. After this, they leave the beaches for the ocean.