Otaria flavescens
The species where the name sea lion stops being a metaphor.
Look at a bull South American sea lion and the naming makes sense at once. He has a golden mane over head, neck and shoulders, a head like a boulder, and a habit of sitting upright with his chin in the air. Older English and German names for the species translated simply as "maned seal."
The skull underneath is genuinely extreme. Of all fifteen eared seal species, the adult male of this one has the most heavily built skull and the most prominent bony ridge running along the top of it. In some individuals the attachment pit for the jaw closing muscle takes up about half the length of the lower jaw. The snout is short, wide and blunt, turned upward, and the neck is so thick there is almost no taper from head to shoulder. This is an animal built to bite hard and to shove.
Two scientific names are in current use, Otaria flavescens and Otaria byronia. IUCN files its assessment under byronia, most South American researchers prefer flavescens, and both refer to the same animal.
All eared seals have males larger than females, but this species pushes it further than any other sea lion. IUCN gives males 2.1 to 2.6 m and 300 to 350 kg against females of 1.5 to 2.0 m and up to about 170 kg, so a bull runs two to three times a female's mass. Other standard references put maximum male length at 3 m, and that disagreement is real, so the safe statement is about 2.3 to 2.6 m with occasional reports to 3 m. That gap exists because only a small share of males ever hold breeding ground, so bulk and a heavy skull are what decide who breeds.
The rest of the eared seal toolkit is on display here too. His ear flaps are short scroll like cones, easily lost in the mane on a big bull, where a true seal would have only a hole. He swims by rowing with long black front flippers rather than sweeping his rear end from side to side, and on land his hind flippers rotate forward under the body so he can carry his weight on all four limbs. That is what lets him hold his chest high and his muzzle pointing at the sky, a posture no true seal can manage, and it is also what lets a bull charge across a rookery at a rival.
Females look like a different species: distinctly lighter, nearly yellowish, often dull yellow on the head and neck, with pale markings around the face and no mane at all. Pups are born black above with grey orange undersides, moult at one to two months to dark chocolate, then fade over the first year to pale tan.
At Punta Norte on the Peninsula Valdes in Argentina, killer whales do something almost no other killer whales in the world do. They ride a wave up onto a shelving gravel beach, partly stranding themselves, grab a sea lion pup off the shoreline, and then wriggle back into the water on the backwash.
The IUCN assessment records the behaviour directly, noting that killer whales there are known to surf in on waves, partially beaching themselves, to take young sea lions off the shoreline. It is one of only two places on Earth where deliberate stranding is a regular hunting technique, and the beach became famous when it was filmed for television in 1990.
The timing is not random. The attacks cluster around high tide, when the water reaches the steepest part of the beach, and around the weeks when that year's pups are first entering the shallows and learning to swim, roughly mid February to April. A pup first goes in the water at about four weeks old. That is the window.
South American sea lions have a violent social life, and the science on it is unusually detailed. A breeding bull typically holds a group of four to ten adult females, though groups up to about eighteen have been reported, and he will grab an oestrous female, drag her, and throw her back inland away from the water to stop her leaving.
Young males who cannot win a territory do not simply wait. They form groups and mount coordinated raids on harems, charging through and scattering the females, which separates mothers from pups. During these raids some subadult males abduct pups outright, then herd and guard them exactly the way an adult male herds females, treating a pup as a substitute for the female they cannot get. Pups are often injured or killed in the process.
The same behaviour gets turned on another species. A small percentage of subadult and adult males in Peru, Argentina and Uruguay attack South American fur seals, and the two patterns are worth separating. Adult and subadult males hunt fur seal pups alone and eat them. Subadult males abduct fur seals as female substitutes, herd them, attempt to mate with them, usually kill them, and never eat them. In one study about 40 percent of the fur seal pups attacked died, and mothers who attempted a rescue succeeded in only one case out of 31.
The species is listed as Least Concern with a stable trend, and it is stable or increasing across most of its range. Chile went from about 137,000 to about 197,000 animals in seven years, northern Patagonia is growing at around 6 percent a year, and commercial harvesting is banned everywhere in the range.
The total, though, needs care. The current IUCN assessment contradicts itself inside one document: its summary says approximately 425,000 animals, while its population section concludes at least 445,000. The country by country breakdown adds up to roughly 445,000, about 197,000 in Chile, 123,000 in Argentina, at least 105,000 in Peru, 12,000 to 13,000 in Uruguay, about 7,500 in the Falklands and no more than 200 in Brazil. A figure of 265,000 circulates widely online and is simply out of date. No estimate of mature individuals is given at all.
Two parts of the story stay unresolved. In the Falkland Islands the population collapsed by about 95 percent, from more than 380,000 animals to fewer than 30,000, and whether that was commercial sealing or a change in the ocean is still argued about. Uruguay is the one clearly declining population, falling around 2 percent a year with no confidently identified cause. Over the whole range the largest threat is climatic: in the 1997 to 1998 El Nino, Peru's population fell from 144,087 animals in December 1997 to 27,991 a year later, an 81 percent reduction, before recovering to about 118,000 by 2006.
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