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 Southern Elephant Seal

Image Credit: NOAA


 Southern Elephant Seal
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  Point Source - Oil Spills
Non-Point Source - Runoff
El NiƱo
Overfishing
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Scientific Name: Mirounga leonina

Category: Pinnipeds

Southern elephant seals are the largest seals on earth and are cousins to the Northern elephant seals. They live in open oceans near Antarctica and are occasionally seen as far north as Tasmania, the little island off the southeast edge of Australia. There are about 600,000 seals worldwide. The male seals are known for their elephant trunk-like noses which are used to make loud, roaring noises to impress the females during mating season. The southern elephant seals are silvery-brown in color and have large square-shaped heads. They use their flippers to steer in the water. The cylinder shape of their bodies enables them to swim and dive at high speeds. The males are much larger than the females, with the males weighing in at more than 3636kg (8000 lbs) and 6.6m (21 feet) in length. The smaller females average 680kg (1500 lbs) in weight and are 3m (10 feet) in length. The largest male ever recorded weighed in at more than 5,000kg (11,000 lbs) more than four times the weight of your entire class!

Scientists think the southern elephant seal can live up to 23 years, but very little research has been done on the seals. While they can dive more than 1000m (3300 feet) down into the ocean, staying down for as much as two hours, the seals normally dive only to depths of 300-600m (1000-2000 feet) and stay down for no more than 20 minutes. They can often slow their heart rates down to one beat per minute underwater. The seals also have more red blood cells than most other marine mammals and this, along with the slow heart rate, helps them to store the air they breathe and to use it more efficiently. When the seals do come up for air, they need only a short time to rest and breathe before diving again. The seals spend almost all of their time underwater. They are excellent swimmers, and as is customary with mammals that swim, they are very awkward on land. They even have trouble getting out of the ocean and up onto the beaches.

Southern elephant seals return from the open ocean to their breeding islands in August and September, with the males arriving first. More than half the entire species population breeds on South Georgia Island, off South America. This island is almost totally uninhabited by humans except for the British Governor, the Postmaster and the scientific crews who stop off here on their way to Antarctica. This allows the seals to breed in peace and quiet. They usually travel up to 2,000km to their breeding ground and return another for 2,000km to where they feed in the open oceans after breeding. The males fight for breeding space by making loud trumpeting sounds, hitting each other with their large noses, and biting with their teeth. These battles can be very bloody and older males have many scars from them. There are very few winners, but the winners become the masters of the beach. In their territories these champions collect a group of up to 100 females called a harem and they breed with them. Males defend their territories by staying on the beach and this means they do not eat for several months, living off their stored blubber. After mating, the seals return to the ocean to feed and then come back again to the beaches to molt during the southern hemispheres late summer and early fall.

Within ten days of arriving at the breeding islands, the females generally give birth to one pup. Because the females are pregnant for almost an entire year, they must breed within a few weeks of giving birth. After the pups are born, the mother does not eat, but waits for her pup to be able to feed on its own. She can then return to the ocean to feed. Pups feed on their mother's milk which is one-half fat and very rich in nutrients, so they grow very quickly. The pups have dark brown to black fur when born, but the fur turns silvery-gray at about four weeks. At three weeks, they usually weigh four times what they weighed when they were born and the pups are left on their own. This can be very dangerous for them on crowded beaches with males that weigh several tons. At about two months of age, the pups migrate to the ocean and teach themselves how to swim.

The southern elephant seals eat squid, large fish, sharks, crabs, shrimp, and penguins. On occasion they dive several thousand feet to feed. While they are similar in size as adults, and have almost no enemies, the pups and juveniles are preyed upon by orca whales and leopard seals. The southern elephant seals feed in the pack ice off the Antarctic shelf. In the 18th and 19th century, the southern elephant seal was hunted for its blubber oil and it wasn't until 1964 that the hunting was governed by laws. Today they are protected by an international agreement between countries called the Convention for the Conservation of Antarctic Seals (CCAS). The general population has decreased by one-half in the last forty years, but the breeding population on South Georgia Island is stable. Scientists do not know why the population has gotten smaller, but believe it is due to the lack of food. Fishermen are now occasionally finding southern elephant seals tangled in their nets and the seals are also affected by ocean pollution, especially floating oil slicks. In the last few decades, tourists have begun to visit the southern oceans and Antarctica. The presence of the tour boats has disturbed the southern elephant seals in the breeding grounds. In the last ten years, several marine nature reserves have been established near Australia's Macquarie Island in the southern Pacific Ocean and off the coast of Tasmania to protect the seals' feeding and breeding grounds. Argentina's Peninsula Valdes at the southernmost tip of South America has been declared a World Heritage Site for the southern elephant seal.




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