Elephant seal

"Sea elephant" redirects here. This may also refer to sea slugs of superfamily Pterotracheoidea.

Elephant Seal
Male and female Northern Elephant Seals
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Suborder:	Pinnipedia
Family:	Phocidae
Genus:	Mirounga
Species
M. angustirostris M. leonina

Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the Northern Elephant Seal (M. angustirostris) and the Southern Elephant Seal (M. leonina). Both were hunted to the brink of extinction by the end of the nineteenth century, but numbers have since recovered. The Northern Elephant Seal, somewhat smaller than its southern relative, ranges over the Pacific coast of the U.S., Canada and Mexico. The most northerly breeding location on the Pacific Coast is at Race Rocks, at the southern tip of Vancouver Island in the Strait of Juan de Fuca. The Southern Elephant Seal is found in the southern hemisphere on islands such as South Georgia, Macquarie Island, and on the coasts of New Zealand, South Africa, and Argentina in the Peninsula Valdés, which is the fourth largest elephant seal colony in the world.

Description

Male Southern Elephant Seal in Kerguelen Islands

Elephant seals take their name from the large proboscis of the adult males (bulls) which resembles an elephant's trunk.^[1] The bull's proboscis is used in producing extraordinarily loud roaring noises, especially during the mating season. More importantly, however, the nose acts as a sort of rebreather, filled with cavities designed to reabsorb moisture from the animals' exhalations. This is important during the mating season when the male seals rarely leave the beach to feed and therefore must conserve body moisture as they have no incoming source of water. Bulls of both the Northern Elephant Seal and the Southern Elephant Seal reach a length of 16 ft (5 m) and a weight of 6,000 lb (2,700 kg) and are much larger than the cows, which typically measure about 10 ft (3 m) and 1,900 lb (900 kg).^[2][3] The largest known bull elephant seal weighed 11,000 lb (5,000 kg) and measured 22.5 ft (6.9 m) in length. This makes the elephant seal the largest member of the order Carnivora.

Physiology

Skull of a northern elephant seal

Male Northern Elephant Seals fighting in California

Elephant seals spend upwards of 80 percent of their lives in the ocean. They can hold their breath for more than 100 minutes^[4][5]—longer than any other non-cetacean mammal. Elephant seals dive to 1550 m beneath the ocean's surface^[6] (the deepest recorded dive of an Elephant Seal is 2,388 metres (7,835 ft) by a Southern Elephant Seal).^[7] The average depth of their dives is about 300 to 600 metres (2,000 ft), typically for around 20 min for females and 60 min (1 hour) for males, as they search for their favorite foods, which are skates, rays, squid, octopuses, eels, penguin (Southerns only), and small sharks. Their stomachs also often contain gastroliths. While excellent swimmers, they are also capable of rapid movement on land, where they have a higher speed than the average human when moving over sand dunes.

Elephant seals are shielded from extreme cold by their blubber, more so than by fur. The animals' hair and outer layers of skin molt periodically. The skin has to be re-grown by blood vessels reaching through the blubber. When molting occurs, the seal is susceptible to the cold, and must rest on land, in a safe place called a "haul-out". While the molt is taking place the bulls cease fighting with one another as there are not breeding harems and females in estrous to protect. Northern males 'haul out' in August, and females in May–June.

Elephant seals have a very large volume of blood, allowing them to hold a large amount of oxygen for use when diving. They have large sinuses in their abdomens to hold blood and can also store oxygenated blood in their muscles with increased myoglobin concentrations in muscle. In addition they have a larger proportion of oxygen-carrying red blood cells. These adaptations contribute to allow the elephant seal to dive to such depths and remain underwater for up to 100 minutes.

Lifespan

Female elephant seals have an average life expectancy of about 23 years, and can give birth starting at the age of 4–5. Males reach maturity at five years, but generally do not achieve alpha status until the age of 8, with the prime breeding years being between ages 9 and 12. The average life expectancy of a male elephant seal is 20 years. Only 1 in 10 males will become an alpha or beta male.

Gallery

Elephant seals (Mirounga angustirostris) on a beach, San Simeon, California	Male, female and pup	Northern Elephant Seals during moulting season near San Simeon, California, USA	Two bull males fighting
Elephant seal snout	Juvenile southern elephant seal

See also

• Marine Mammal Center
• Penelope seal

References

External links

• Tagging of Pacific Predators, Elephant Seals
• Friends of the Elephant seal
• Elephant Seal Research Group
• Elephant seals
• Dr. Daniel Costa's Research Laboratory
• Elephant Seals at Race Rocks, Canada