EARED SEALS

Steller Sea Lion (Eumetopias jubatus)

The Steller Sea Lion (Eumetopias jubatus), otherwise known as the Northern Sea Lion, was named after Georg Wilhelm Steller, a German zoologist who first described them, with the latin name coming from a description of their broad foreheads and neck manes. Found from eastern Russia across to western North America, the species are spread as far south as California, but unfortunately are now classified as Near Threatened, with one subspecies Endangered. Estimated population size = 160,867.
E. jubatus are the largest eared seals, or otariids, in the world (males up to 3.3 m long/ 1,120 kg, females up to 2.9 m/ 350 kg). They have long, broad, black fore flippers which are covered in a thin fur except for at the tips, and shorter, stumpier hind flippers. E. jubatus are heavily built animals, appearing particularly muscular in the shoulders and chest. Males are strikingly large and heavy, and sexual dimorphism is very apparent in the species, with the males sporting diagnostic enlarged crowns that tell them apart from the females. Not only this but they also have thick, shaggy-looking manes, often in a paler colour, that are visible around their necks and backs. Facially, both sexes are quite dog-like, with rounded heads and pale vibrissae. Colouration can be almost a pale blond, through to a light brown, and right up to darker brown with reddish patches in some places. While many pinnipeds look very dark when wet, Steller Sea Lions are unusual in that they often appear pale coloured even in water. Both sexes can have mottled colour and blotches, as well as scarring on their bodies.
Feeding behaviour:
The opportunistic diet of E. jubatus mostly consists of fish and invertebrates. Studies have found common species to be pollock, cod, mackerel, herring, flatfish, salmon, rockfish, squid and octopus, though it is thought this varies with location, season, sex, and even time of life. For example, mothers with pups forage predominantly at night, and therefore take different prey to non-breeding individuals that are hunting during the day. Long foraging trips often take place over the winter, and these may be pelagic and include deep dives, but they have also been known to venture into freshwater to fish. In addition, larger individuals have been observed preying on young Northern Fur Seals, Harbour Seals, and Ringed Seals, as well as the occasional Sea Otter, though this isn’t commonplace.
Breeding behaviour:
Sexual maturity – males 3-7 years old/ females 3-6 years old.
E. jubatus, as other eared seals, are polygynous. Older mature males congregate on beaches or rookeries in late spring and summer, and defend their own territories, gaining the right to mate with multiple females. Gestation lasts a year (including a 3 month period of delayed implantation), and pups are generally born from May to July. These youngsters have thick, dark brown lanugo, which is moulted by 6 months of age, and the mothers remain by their side solidly for the first 1-2 weeks. After this she will maintain a cycle of foraging at sea and returning to land to nurse, gradually extending the time she is away from the pup. Most juveniles are weaned at around a year, though it is not unusual for this to continue for another year or so, and a mother may give birth to a second pup whilst still suckling her first. Breeding rookeries break up and disperse in the summer, but both sexes haul out to moult in the autumn. Life expectancy reaches around 30 for females, and 20 for males.
There are currently two recognised subspecies of E. jubatus:
Western Steller Sea Lion (Eumetopias jubatus jubatus)
Loughlin’s Steller Sea Lion (Eumetopias jubatus monteriensis)

Photos: Debs Allbrook

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