Is it a “seal” or a “sea lion”? These terms are often confused. Pierre Constant offers some clarification and gives us insights into the different species of pinnipeds we know and love.
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A long time ago (in the last century, in fact), I used to be a naturalist guide in the Galápagos Islands. Lasting over a month, the guide’s training at the Galápagos National Park, under the auspicious and beneficial care of the Charles Darwin Research Station, was a serious affair. After the academic course, with classes led by scientific authorities and hours of self-study in the scientific library, there was a four-hour final exam to test your acquired knowledge. If you passed, you would be awarded the coveted naturalist guide’s license, which would allow you to work officially on cruise ships and sailing boats in the Galápagos National Park, a World Heritage Site since 1978.
Depending on where you went in the archipelago and which islands and sites you visited, you were enchanted by colonies of endemic Galápagos sea lions (Zalophus wollebaeki) lazily basking in the sun on white, green, red or black sandy beaches. In some places, west of Santiago or Isabela Island, exposed to an upwelling of the cold-water Cromwell Current, you encountered a different species: the Galápagos fur sealion (Arctocephalus galapagoensis), whose ancestor (Arctocephalus australis) had migrated from Antarctica along the coast of Chile and Peru with the well-known Humboldt Current.
The right terms
Every time I heard people refer to these mammals as “seals” or even “fur seals”, I was slightly agitated, not to mention truly irritated at times. I made it a point to systematically explain to visitors the difference between a seal and a sea lion. But some hard-headed individuals, thinking they knew better, would never get it or would continue with the wrong term just because “it has always been called that”.
Seals and sea lions are pinnipeds, a diverse group of semi-aquatic marine mammals, which used to be commonly known as earless seals (or true seals) and fur seals. The so-called true seals belong to the family Phocidae. Sea lions, on the other hand, belong to the family Otariidae, which has two distinct subfamilies: Arctocephalinae, which has two genera, and Otariinae, which has five genera. Walruses in the Arctic belong to a separate family—the Odobenidae.
In general, sea lions are mostly from the southern hemisphere—except for the California sea lion (Zalophus californianus), the ancestor of the Galápagos sea lion, and the Steller sea lion (Eumetopias jubatus) of the Arctic. Seals, on the other hand, are mostly from the northern hemisphere—with the exception of the southern elephant seal (Mirounga leonina), crabeater seal (Lobodon carcinophaga), Weddell seal (Leptonychotes weddellii) and leopard seal (Hydrurga leptonyx), a famous inhabitant of Antarctica and a ferocious predator of penguins.
Physical differences
The main difference between seals and sea lions is that seals have round eyes and a pointed nose. They have no visible ears and creep on their stomachs for locomotion. Sea lions have almond-shaped eyes, a square muzzle and external (tube-like) ears. They can move forward on their front flippers, which also helps them stand erect from the belly up as if using a pair of crutches. What people commonly call a “fur seal” is, therefore, a mistake and totally erroneous, as they are, in fact, fur sea lions. They have a so-called thick double fur but have all the characteristics of a sea lion, albeit smaller in size, with a noticeably more pointed nose.
In the family Otariidae, the subfamily Arctocephalinae comprises two genera: Arctocephalus, or southern fur sea lions (eight species) and Callorhinus, northern fur sea lions, with only one species, Callorhinus ursinus, found in the Arctic Ocean. It is interesting to note that all eight species of Arctocephalus have, in fact, originated from the Antarctic at a time when living conditions were not as extreme and polar as they are now.
This led to speciation as different groups of the original South American fur sea lion (Arctoceph-alus australis) migrated in a northern direction in search of a better environment, using the marine currents flowing northward, such as the Humboldt Current for the Juan Fernández fur sea lion (Arctocephalus philippii) and the Galápagos fur sea lion, or the Benguella Current for the Cape fur sea lion (Arctocephalus pusillus pusillus). The Australian fur sea lion (Arctocephalus pusillus doriferus) and New Zealand fur sea lion (Arctocephalus forsteri) followed similar routes to reach their final destination in southern Australia and New Zealand.
Next time you hear someone talking about fur seals, make sure you brief them on the correct denomination. The old one is obsolete and misleading. You’ll make my day! ■
