Steller sea lion


The Steller sea lion (Eumetopias jubatus), also known as the Steller's sea lion and northern sea lion, is a near-threatened species of sea lion in the northern Pacific. It is the sole member of the genus Eumetopias and the largest of the eared seals (Otariidae). Among pinnipeds, it is inferior in size only to the walrus and the two species of elephant seals. The species is named for the naturalist Georg Wilhelm Steller, who first described them in 1741. The Steller sea lion has attracted considerable attention in recent decades, owing to significant and largely unexplained declines in their numbers over an extensive portion of their northern range in Alaska.

Adult animals are lighter in color than most sea lions, ranging from pale yellow to tawny and occasionally reddish. Steller sea lion pups are born almost black, weighing around 23 kg (51 lb), and remain dark in coloration for several months. Females and males both grow rapidly until the fifth year, after which female growth slows considerably. Adult females measure 2.3–2.9 m (7.5–9.5 ft) in length, on average being 2.5 m (8.2 ft), and weigh 240–350 kg (530–770 lb), with an average of 263 kg (580 lb).[3][4] Males continue to grow until their secondary sexual traits appear in their fifth to eighth year. Males are slightly longer than the females, growing to about 2.82–3.25 m (9.3–10.7 ft) long and averaging 3 m (9.8 ft) in length.[5] Males have much wider chests, necks, and general forebody structure. Males can weigh between 450–1,120 kg (990–2,470 lb), weighing on average 544 kg (1,199 lb).[6][7][8] Males are further distinguished from females by broader and higher foreheads, flatter snouts, and a thick mane of coarse hair[9] around their large necks. It is fitting then that their Latin name translates roughly as "maned one with the broad forehead".

The range of the Steller sea lion extends from the north shore of Honshu in Japan to the Gulf of Alaska in the north, down to Año Nuevo Island off the coast of central California to the south. They formerly bred as far south as the Channel Islands, but have not been observed there since the 1980s. Based on genetic anаlyses and local migration patterns, the global Steller sea lion population has traditionally been divided into an eastern and western stock at 144°W longitude, roughly through the middle of the Gulf of Alaska.[10][11] Recent evidence suggests the sea lions in Russia in the Sea of Okhotsk and the Kuril Islands comprise a third Asian stock, while the sea lions on the eastern seaboard of Kamchatka and the Commander Islands belong to the western stock.

In the summer, Steller sea lions tend to shift their range somewhat southward. Therefore, though there are no reproductive rookeries in Japan, several consistent haul-out sites are found around Hokkaidō in the winter and spring. Vagrants have been spotted in the Yellow Sea and Bohai Gulf and along the coast of the Korean Peninsula and China.[1][12] The oldest fossil known of the species was found near Kanazawa, Japan and dates to the late Early Pleistocene (0.8 Ma).[13]


Skeleton
Steller sea lions congregate on rocks in the Gulf Islands of British Columbia, Canada
Sea lion with white sturgeon
Adult bull, females, and pups near Juneau, Alaska, the US
Steller sea lion pup on Antsiferov Island in the Kuril Islands, Russia.
Sea lion releasing air underwater
Sea lions haul out on Amak Island
Near Vancouver Island