Steller sea lion (Eumetopias jubatus) COSEWIC assessment and status report: chapter 5

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Species Information

• Name and Classification
• Description

Name and Classification

The Steller sea lion (Eumetopias jubatus Schreber 1776) is the largest member of the Family Otariidae(order–Carnivora, suborder–Caniformia, Kenyon and Scheffer 1955; Jefferson et al. 1994; Rice 1998). It was named after the German naturalist George Wilheim Steller who described the species in 1742 (Miller and Miller 1848). Other common names are Steller’s sea lion, northern sea lion, Otarie de Steller (Fr), sivuch (Ru), todo (Jp), lobo marino de Steller (Sp), qawax (pronounced ka-wa by Aleut natives), and wiinaq (Alutiiq). Its scientific name means having a well-developed broad forehead (Eumetopias–Greek) and a mane (jubatus–Latin). 

Description

Steller sea lions exhibit significant sexual dimorphism (Fiscus 1961; Mathisen et al. 1962; Thorsteinson and Lensink 1962; Orr and Poulter 1967; Calkins and Pitcher 1982; Loughlin and Nelson 1986; Calkins et al. 1998; Winship et al. 2001). Adult females (cows) average 2.1-2.4 m and 200-300 kg. Adult males (bulls) are noticeably larger, attaining a length of 2.7-3.1 m and weighing 400-800 kg, although the largest can weigh over 1100 kg as they fatten prior to the start of the breeding season. Mature males develop a prominent ‘mane’ of course hair on their massive muscular necks and chests, from which they derive the name ‘lion’. The shape of their heads tends to be more robust with a flatter snout than that of females.

Pups are born from late May to early July and weigh 16-23 kg at birth, with males weighing more on average than females. Pups are born with a thick blackish-brown lanugo that is moulted between 3-6 months of age (Scheffer 1964; Vania 1972). 

Coloration of dry juveniles and adults is pale yellow to light tan, darkening to chocolate brown on their undersides and near their flippers (which are black and bare-skinned). When wet, Steller sea lions appear greyish white. Pelage of both sexes is comprised of short coarse hairs (Scheffer 1964). Steller sea lions undergo an annual moult shedding their entire pelage, but not the epidermis. Non-reproductive females appear to moult first, beginning as early as late June, and in other age-classes the process extends into early December (Vania 1972; Calkins and Pitcher 1982). 

Adult vocalizations in air consist of deep-throated bellows and roars. Territorial males wheeze as part of their threat displays (Orr and Poulter 1967; Gentry 1970), and produce a loud guttural sound both in the air and underwater(Schusterman et al. 1970). Newborns tend to bleat like sheep.

Steller sea lions are capable of propping themselves on their foreflippers and rotating their hind flippers forward, rendering them remarkably agile on land. Animals can climb steep rocks and are often found many metres above the sea surface. Animals tend to be highly gregarious while on land and generally pack close together with little or no separation.