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Gregory R. Mann, Ph.D. {ret.}

Southern Elephant Seal

“Mirounga leonina”

Southern Elephant Seals are named for their elephant trunk-like noses. Adult males are larger than the females and sizes also range within the same-sex in this species. They are enormous in size being the largest pinniped species. Adult males weigh between 2,200-4,000 kilograms are average length of 4.2 meters with a maximum of 6.2 meters. Male Southern Elephant Seals at Argentina’s Peninsula Valdés are smaller than males in the Falkland Islands & South Georgia Island. Females typically weigh 500-1,000 kilograms measure 2.7-3.7 meters in length. Adult Southern Elephant Seals range in color from dark gray to brown with lighter coloring on the chest. They live for up to 23 years and are found around the sub-Antarctic islands near the Antarctic polar front. South Georgia Island is home to the largest population with more than half of the entire species. Other populations are found at Macquarie Island, Heard Island and the Kerguelen Islands. Rare births of Southern Elephant Seals have also been reported in New Zealand, Australia, South Africa and some wandering individuals have been found as far north as the equator. The total population of Southern Elephant Seals has been calculated at about 600,000.

Southern Elephant Seals inhabit open water outside the breeding & molting seasons for an average of 10 months per year to feed on squid & fish. During this time, the seals dive day and night to average depths of 300-600 meters for 20-22 minutes. Their deepest dives are made during daylight hours. They have been known however, to dive as deep as 2,000 meters for as long as 2 hours. As much as 90% of their time is spent beneath the surface, coming up to breathe for 2-3 minutes between dives. Adult Southern Elephant Seals return to their feeding grounds in the Antarctic twice annually traveling up to 2,000 kilometers each way, once following breeding season and the second after molting. Females reach sexual maturity between 2-4 years of age, giving birth to one pup annually, although some have been observed nursing 2 pups. Males reach sexual maturity between 3-6 years of age but do not begin breeding until about 10 years of age. Females give birth & breed in September-November 1-10 days after coming ashore. The mother does return to sea to feed until her pup is weaned. She lives on her blubber generally losing about 35% of her body weight or up to 8 kilograms per day. Southern Elephant Seal pups are born with dark brown-black fur, which they will molt about 1 month later for a shorter coat of gray hair. They measure about 1.3 meters long and weigh 45-50 kilograms as newborns and 135-140 kilograms by the time they are weaned about 23 days later.

Dominant breeding Southern Elephant Seal males arrive a month before the females and smaller males to fight for dominance & females. Only 2-3% of males are successful winning “breeding rights” to large numbers of females, exceeding 100 in some cases. The mother mates between 3-5 days before her pup is weaned, then returns to sea after mating to feed. Pups leave the breeding ground 3-8 weeks later to feed. If food is not readily available, pups depend on their body reserves to survive. Pup mortality can be high in heavily populated breeding territories. Adult male Southern Elephant Seals which are often up to 10 times the size of breeding females, also do not feed during the breeding season and can lose more than 40% or 12 kilograms per day of their body weight. The amount of time spent ashore by males during the breeding season varies greatly ranging from 60-90 days onshore. Females typically spend about 1 month onshore. Following the feeding period, adults return to molt in January-February for 30-40 days, again remaining ashore without feeding for the duration.

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