Arctocephalus pusillus
The biggest fur seal in the world, and the one that keeps behaving like a sea lion.
Most fur seals are small animals. This one is not. The brown fur seal is the largest of the nine fur seal species, roughly twice the bulk of a typical Arctocephalus, and it lives in two widely separated places under two different names.
The Cape or South African subspecies holds about 3,000 km of southwestern African coast, from southern Angola through Namibia to Algoa Bay in South Africa. The Australian subspecies is endemic to southeastern Australia, centred on Bass Strait between Tasmania and Victoria. South Africa's national assessment gives Cape bulls 2.0 to 2.3 m and an average of 247 kg, with females 1.2 to 1.6 m and an average of 57 kg. Australian males run 201 to 227 cm and 218 to 360 kg, and Australian females 136 to 171 cm and 41 to 113 kg. Sources genuinely disagree about which of the two is the larger animal, so it is fair to say only that both are enormous by fur seal standards.
The total population is estimated at roughly 2.12 million, split as about 2 million Cape fur seals and 120,000 Australian fur seals, and the IUCN lists the species as Least Concern with an increasing trend. The Australian side is less settled. Pup production there went 19,820 in 2002/03, 21,881 in 2007/08, then 15,063 in 2013/14, a drop the assessors could not separate from a single bad season.
Everything about this animal's body says fur seal. It has the family's two layer coat: thick waterproof guard hairs on the outside, and beneath each of them a bundle of 35 to 40 fine underfur hairs that traps a permanent layer of air against the skin. It has the small external ear flaps that give the eared seals their name, long and prominent here, with the flaps and their bases often paler than the fur around them. It has long fore flippers, and like every eared seal it swims by flapping those front flippers like wings rather than sculling with its hind end. On land it turns its hind flippers forward under the body and walks on all four limbs.
Then the behaviour goes off script. Other fur seals space themselves out on a beach. This one lies pressed against its neighbours in heaps, a habit biologists call thigmotactic, exactly the way sea lions do. It walks with a sea lion's alternating gait. It sounds like a sea lion. Its head is broad and its muzzle is the least fur seal like in the family, blunt and heavy with a bulbous fleshy nose.
None of that is an accident. Genetic studies keep placing Arctocephalus pusillus closer to the sea lions than to the other members of its own genus, which means the genus as currently written does not describe a single branch of the family tree. The formal difference between the two subspecies is far less dramatic: a larger bony crest at the back of the skull, described by Repenning and colleagues in 1971. That, plus an entire ocean between them.
Seals were being clubbed on Robben Island by at least 1591. In 1610 Dutch ships took 45,000 skins. In the first five years after settlement at the Cape, from 1653 to 1657, another 71,523 skins were exported. A reconstruction by David and van Sittert puts the harvest from 1652 to 1752 at about 1.28 million animals, and the total killed in southern Africa before 1900 at no less than 1.93 million.
By the 1890s at least 23 island colonies had been emptied completely. On Possession Island in Namibia, 40,000 seals were reported killed in a single season, and the colony was gone by 1828. The twentieth century was worse in raw numbers: 2.5 million animals between 1900 and 1989, of which 2.2 million came after 1950. South Africa suspended commercial harvesting in 1990, and killing seals for profit is now illegal there.
Namibia did not stop. It runs the only commercial seal harvest in the southern hemisphere, at three mainland colonies. Verified figures from the IUCN assessment are 43,168 pups and 4,573 adult males in 2010, and 45,794 pups and 3,626 adult males in 2011. The reported annual quota is far higher, around 80,000 pups and 6,000 bulls, but actual kill numbers are well below quota and are not published transparently. A quota and a kill are different things, and it is worth keeping them apart.
On 7 June 2024, rabies was confirmed in a wild Cape fur seal from Big Bay near Cape Town. Nothing like it had happened before. There had been a scattering of one off rabies cases in marine mammals across all of recorded history, and every one of them was a dead end. This one was not.
Retrospective testing and genetic dating place the real start of the outbreak at around August 2022. The virus came from a single spillover of a dog related rabies variant carried by black backed jackals, which patrol the same Namibian beaches where the seals haul out. From there it has been passing seal to seal, which is the part that had never been documented anywhere. Researchers have also confirmed transplacental infection, meaning a pregnant female can pass it to her unborn pup.
The share of tested seals coming back positive rose to 22 percent in 2024 and 36 percent through October 2025, and rabies has now been declared endemic in the population. As of May 2026 the World Organisation for Animal Health had recorded more than 100 confirmed cases across South Africa and Namibia and more than 145 human exposure incidents. No person has developed rabies, because everyone bitten received treatment in time. The official advice on both coastlines is now simple: keep well clear of seals on the beach.
Cape fur seals are generalists, taking Cape hake, horse mackerel, pelagic goby, pilchard, anchovy, squid, rock lobster, shrimp and prawns. A small number of individuals specialise in African penguins and Cape gannets, but that is a few animals rather than the population. Australian fur seals feed mostly on the bottom, on redbait, leatherjackets, jack mackerel, barracouta, flathead, squid, octopus and cuttlefish. Most Cape fur seal dives on the South African west coast are shallower than 50 m and last one to two minutes, with a maximum recorded depth of 204 m. Australian females usually work 65 to 85 m, with a maximum of 164 m and a longest recorded dive of 8.9 minutes.
One recorded event breaks every pattern. In December 2012, about 20 nautical miles southwest of Cape Point, a single male Cape fur seal was filmed attacking, killing and partly eating five blue sharks, each one to one and a half metres long. He tore each shark open and ate only the liver and internal organs. The observation was published in the African Journal of Marine Science in 2015. Nobody had expected to document a seal hunting sharks.
Because this seal eats hake, sardine and anchovy, three commercially valuable stocks, people regularly call for a cull. The modelling does not support it. Punt and Butterworth showed in 1995 that Cape fur seals also eat the predatory fish that eat young hake, so reducing seal numbers could actually lower the hake catch rather than raise it. Meanwhile the seals' own losses to fishing gear are estimated at under 1 percent of population size, and a 2021 Namibian study found that 53 percent of entanglements involved fishing line, that is, gear the fishery itself had lost.
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