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Pinnipednesday - Mirounga leonina Edition

Heavyweight pinniped of the world!

The Southern Elephant Seal (Mirounga leonina) is the largest pinniped and Carnivoran (meaning of the order Carnivora) in the world. That fact might seem surprising, so let me clarify: though the word "carnivore" is often used to refer to any animal which feeds primarily on meat, not all carnivores belong to the order Carnivora. And bull Southern Elephant Seals easily outweigh the walrus, the polar bear and the Kodiak bear, making them the largest Carnivoran on earth. They are called Southern Elephant Seals due to their size and the proboscis the adult males develop.


Southern Elephant Seals are larger than Northern Elephant Seals, and the Southern bulls actually have shorter proboscises than the Northern bulls. There is pronounced sexual dimorphism between adult males and adult females, with the males weighing almost 6 times more than the females - arguably the most significant sexual dimorphism by body mass of any mammal. Bulls can weigh up to 8,800 pounds (4,000 kg) and measure 19 feet (5.8 meters) in body length. The largest bull ever recorded was killed in Southern Georgia of the South Sandwich Islands in 1913, and weighed in at a massive 11,000 pounds (5,000 kg). He was 22.5 feet (6.85 meters) long. Females are much smaller, weighing about 1,980 pounds (900 kg) and growing almost 10 feet (3 meters) long.

Southern Elephant Seals are champion divers and regularly dive to depths up to 3,300 feet (1,000 meters) to hunt squid and fish in the open ocean, which makes them deepest-diving non-cetacean mammal. The deepest a Southern Elephant Seal has ever been recorded is a depth of almost 7,000 feet (2,133 meters). It's likely that their large eyes help them to see the bioluminescence of their prey. When they are gathered along the sub-Antarctic coast, they expand their diet to include other kinds of fish, krill, crustaceans, and molluscs.


During mating season, the Southern Elephant Seal bulls arrive early to establish beach territories amongst themselves, so that they can start harems. When the competition escalates to the level of actual fights, they can be bloody and brutal. The bulls will rear up and slam into each other's necks and chests, ripping the flesh with their teeth. Once a bull has established his territory and his harem, he must stay on the beach or risk losing both. This means months of fasting and living off fat stores. Females will give birth to the pups from the previous year's mating season and nurse them continuously for 23 days, living off of their own stores of fat.


Like many other pinniped species, Southern Elephant Seals were heavily hunted during the 18th and 19th centuries and resulted in a significant population decline. After protective measures were put in place to prevent them from being hunted, their various subpopulations began to recover, but in the last 50 years have seen yet another decline. The reasons for this are still unclear, but theories include fisheries providing competition for the Southern Elephant Seals' prey.


Source for all images used in this post.

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