Steller sea lions are impressive animals, and you wouldn’t want to run into one in a dark alley, or even on a fishing dock. A large bull can way over a ton, and they have a have nasty attitudes to go along with all that blubber. For all you Star Wars fans, I’ve always imagined that Jabba the Hutt was created with a Steller sea lion in mind. For this post and the next two, I will write about Steller Sea lions, their biology, distribution, social structure, and some amazing new research pinpointing a surprising possible predator of Stellers.
The Steller or Northern sea lion (Eumetopias jubatus) is a member of the order Pinnipedia, which includes harbor seals and walruses, and it is the largest species in the family Otariidae, the “eared seals”. This family also includes the California sea lion and the Northern fur seal. Otariids, unlike phocids (the “true seals”), have external ear flaps, an elongate neck, long fore flippers used for propulsion, and hind flippers that can rotate, allowing sea lions to use all four limbs for movement on land. They are called sea “lions”, because adult males have thick necks with long fur on the neck, resembling a lion’s mane. Steller sea lions were named after German physician Georg Steller, who was the naturalist on the 1741 Russian expedition led by Vitus Bering.
Steller sea lions are found from southern California, along the coastline of the Pacific rim to northern Japan, but most of the breeding rookeries are located from the Gulf of Alaska to the Aleutian Islands.
Steller sea lions exhibit marked sexual dimorphism. Males, on the average, are 1.3 times longer than females, but they weigh 2.5 times more than females. Adult male Stellers average 1500 lbs. (750 kg) and are 9 ft. (2.7 m) in length. A maximum-sized male can weigh as much as 2500 lbs. (1120 kg) and be 10 -11 ft. (3-3.4 m) in length. Females average 600 lbs. (272.7 kg) and are 7 ft (2.1 m) in length, but may weigh as much as 770 lbs. (350 kg).
A Steller sea lion has a hefty body and a blunt snout. A male has a distinctive forehead and a mane of long hair on the back of his neck, shoulders, and chest. This mane not only protects him from cold air and water temperatures and from jagged rocks on his haul-outs and rookeries, but it also protects him when fighting with other males. Pups are dark brown at birth, and since the tips of their hair are colorless, they appear frosty. Their hair lightens after their first molt. Adults are blonde to reddish- brown with dark- chocolate-brown on their undersides and flippers. Females are usually lighter in color than males. A Steller’s fur is thick and coarse, and they shed or “molt” their fur every year. The molt takes approximately four weeks and occurs in the late summer or early fall.
A sea lion has a streamlined body shaped like a torpedo, which reduces drag when moving through the water. This streamlining is due to a thick layer of blubber under the skin. Stellers have long, wing-like fore flippers that they stroke up and down to thrust themselves through the water in a movement that resembles flying. They use their hind flippers for steering. Unlike harbor seals, sea lions are able to fold their hind flippers under their bodies to walk on land. They are quite agile on land, and an adult male Steller can easily out-run a human.
Stellers, like all eared seals, have small, external ear horns. Biologists believe that hearing is one of the most important senses for a sea lion, and they probably have acute hearing under water and fairly good hearing in air.
Steller sea lions are very vocal. At a haul-out, you may hear growls, roars, and grumbles from the older sea lions, along with lamb-like vocalizations from young pups. Unlike California sea lions, Stellers do not bark.
I’ll have more about Stellers next week. Meanwhile, if you haven’t already done so, visit my home page and sign up for my Mystery Newsletter.