Arctocephalus philippii
The only eared seal in which some males defend a breeding territory made entirely of water.
The Juan Fernández Archipelago sits about 600 km west of ValparaĂso, Chile, and it was the sealing industry's richest and most thoroughly emptied ground. The FAO's identification guide states that sealers' logs, starting in 1687, account for roughly four million seals taken from these islands. A 2022 paper by Alava and colleagues gives a specific tally of 3,870,170 individuals captured between 1687 and 1898.
Two smaller numbers make the abstraction concrete. By 1872 about 38,000 animals had been killed to supply the China fur trade. And in 1801 a single ship carried one million skins to the London market. One ship, one voyage.
The IUCN assessment is careful here, and so should we be. It notes that the harvest between 1793 and 1807 has been estimated in the millions but that no reliable estimates are available. The magnitude is certain. The precision is not.
By 1891 the surviving population was estimated at 300 to 400 animals. From roughly 1900 the species was presumed extinct, and it stayed that way in the scientific literature for six decades.
In 1965 the Chilean scientist Nibaldo Bahamonde reported small groups on Alejandro Selkirk and Robinson Crusoe Islands and announced that the species was not gone after all. Estimates of that relict population run to around 200 animals on Alejandro Selkirk. Chile banned hunting the species that same year and extended full protection to all Arctocephalus species in 1978.
The rebuild has been steady: roughly 750 individuals in 1969, and 32,278 by 2005, with pups born on Alejandro Selkirk rising from 548 in 1983 to 6,941 in 2005. By 2018 researchers knew of 63 colonies across the archipelago, 47 of them on Robinson Crusoe alone.
This species has the longest snout of any southern fur seal, and it is essentially the animal's identity. The muzzle is long, slender, pointed and flat on top, ending in a large, bulbous, fleshy nose with the nostrils angled down. The FAO guide notes that the nose gives bulls a shark like head profile, and researchers have identified wandering individuals thousands of kilometres from home using old photographs and that trait alone. Bulls are blackish brown with the long guard hairs of the mane tipped in silver, so the crown and shoulders look frosted while the throat stays dark.
Everything below the head is eared seal engineering. Long, prominent ear flaps sit clear of the skull. The fore flippers are long and do the propelling, flapped like wings, which is what makes a two week ocean crossing possible for an animal that weighs about as much as a person. The hind flippers are notably short, and like every otariid they rotate forward under the body, so these seals climb the volcanic rock and caves of the archipelago on all fours instead of hauling themselves along on their bellies.
Under the guard hairs sits the dense underfur that made the species worth 3.87 million kills. Nearly every adult male is heavily scarred across the neck and fore flippers from fighting, which tells you what those front limbs are used for on land.
Among all nine fur seals, and indeed among all eared seals, this one does something no other does. Francis and Boness, working through a full breeding season, found that male territories came in three kinds: land locked territories away from the water, shoreline territories, and, in 16 percent of cases, territories that were entirely aquatic, consisting of a patch of open water where females floated.
Roughly half of all observed matings took place in those fully aquatic territories, and a male holding water did about as well as a male holding land.
The reason is heat. The islands are hot, the beaches are volcanic rock, and females move down to the shoreline and into the sea to cool off during the hottest part of the day. Males holding land territories have to abandon them for about 45 minutes at a time just to cool down, which is a serious problem when a rival is watching. Some males solved it by giving up on land entirely and defending the cool water where the females already were.
A nursing female here does something that looks like a mistake until you understand it. Satellite tracking shows foraging trips heading south and west into deep open ocean, averaging 653 km and reaching 889 km from the island, lasting a mean of 12.3 days with the longest recorded at 25 days. Those are among the longest foraging trips of any eared seal.
And yet the dives are almost absurdly shallow. Osman analysed 27,541 dives from five females and found a median depth of 4 m and a median duration of 20 seconds. This is not an animal that goes deep. It is an animal that goes far. The explanation is prey: a diet dominated by lanternfish and the squid Onychoteuthis banksi, which rise into the top few metres of open ocean at night. The food is thin, scattered across enormous distances, and sitting right at the surface, so the seal travels for a fortnight, skims the surface layer, and comes home.
One number from that same study travels around the internet attached to the wrong animal. The deepest single dive recorded in Osman's work was 169.5 m, and it belongs to this species. You will often see a 169 m record credited to the Galápagos fur seal instead. That is a copying error. The Galápagos maximum is 115 m.
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