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Southern Elephant Seal, Paradise Harbor (Paradise Bay), West Antarctica, Antarctica, South Pole

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Published on Jul 11, 2013

The southern elephant seal is one of the two extant species of elephant seals. It is both the largest pinniped and member of the order Carnivora living today, as well as the largest Antarctic seal. The seal gets its name from its great size and the large proboscis of the adult males, which is used to make extraordinarily loud roaring noises, especially during the mating season. Rather larger at average than the male northern elephant seal (Mirounga angustirostris) (which is 40% lighter) and male walrus (Odobenus rosmarus) (the average North Pacific bull, of the larger race, is 2.5 times lighter), the adult bull southern elephant seal is without rival the largest carnivoran alive. An average adult male southern elephant seal weighs six to seven times more than the largest terrestrial carnivorans, the polar bear (Ursus maritimus) and Kodiak bear (Ursus arctos middendorffi). The southern elephant seal is distinguished from the northern elephant seal (which does not overlap in range with this species) by its greater body mass and a shorter proboscis. The southern males also appear taller when fighting, due to their tendency to bend their backs more strongly than the northern species. This seal shows extreme sexual dimorphism in size, seemingly the largest of any mammal by mass, with the males typically five to six times heavier than the females. In comparison, in two other very large marine mammals with high size sexual dimorphism, the northern elephant seal and the sperm whale (Physeter macrocephalus), the males weigh on average about three times as much as the females, and only more than four times as heavy in exceptionally heavy bull specimens. While the females southern elephant seal typically weighs 400 to 900 kg (880 to 1,980 lb) and measures 2.6 to 3 m (8.5 to 9.8 ft) long, the bulls typically weigh 2,200 to 4,000 kg (4,900 to 8,800 lb) and measure from 4.2 to 5.8 m (14 to 19 ft) long. An adult female averages 771 kg (1,700 lb) in mass, while a mature bull averages about 3,175 kg (7,000 lb). Studies have indicated elephant seals from South Georgia are around 30% heavier and 10% longer on average than those from Macquarie Island. The record-sized bull, shot in Possession Bay, South Georgia, on 28 February 1913, measured 6.85 m (22.5 ft) long and was estimated to weigh a hulking 5,000 kg (11,000 lb), although it was only partially weighed piecemeal. The maximum size of a female is 1,000 kg (2,200 lb) and 3.7 m (12 ft). The eyes are large, round, and black. The width of the eyes, and a high concentration of low-light pigments, suggest sight plays an important role in the capture of prey. Like all seals, elephant seals have hind limbs whose ends form the tail and tail fin. Each of the "feet" can deploy five long, webbed fingers. This agile dual palm is used to propel water. The pectoral fins are used little while swimming. While their hind limbs are unfit for locomotion on land, elephant seals use their fins as support to propel their bodies. They are able to propel themselves quickly (as fast as 8 km/h (5.0 mph)) in this way for short-distance travel, to return to water, to catch up with a female, or to chase an intruder. Pups are born with fur and are completely black. Their coats are unsuited to water, but protect infants by insulating them from the cold air. The first moulting accompanies weaning. After moulting, the coats may turn grey and brown, depending on the thickness and moisture of hair. Among older males, the skin takes the form of a thick leather which is often scarred. Like other seals, the vascular system of elephant seals is adapted to the cold; a mixture of small veins surround arteries, capturing heat from them. This structure is present in extremities such as the hind legs. Elephant seals are among the seals that can stay on land for the longest periods of time, as they can stay dry for several consecutive weeks each year. Males arrive in the colonies earlier than the females and fight for control of harems when they arrive. Large body size confers advantages in fighting and the agonistic relationships of the bulls gives rise to a dominance hierarchy with access to harems and activity within harems, being determined by rank. The dominant bulls establish harems of several dozen females. The least successful males have no harems, but may try to copulate with a harem male's females when the male is not looking. The majority of primiparous females and a significant proportion of multiparous females mate at sea with roaming males away from harems. An elephant seal must stay in his territory to defend it, which could mean months without eating, having to live on his blubber storage.

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