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Pinnipednesday - Eumetopias jubatus Edition

This week's edition stars some noisy buggers.

The Steller Sea Lion (Eumetopias jubatus) is the largest of the eared seals and the only extant member of the genus Eumetopias. They can be found on the northern Pacific coast of North America and extends all the way to the Sea of Okhotsk and Kuril Islands in Russia. They have recently suffered some unexplained population declines in the Alaskan part of their range. Steller Sea Lions are named after George Wilhelm Steller, a German naturalist who described the species back in 1741.


Adult Steller Sea Lions tend to have lighter-colored coats than California Sea Lions, whose range overlaps a little. Males and females tend to grow at the same pace until their fifth year of life, after which the females' growth tapers off and the males continue to get bigger and bigger. These males tip the scales at about 2,470 pounds (1,120 kg). They can grow up to be 10.7 feet (3.25 meters) long. Females are smaller, weighing about 770 pounds (350 kg) and growing to 9.5 feet (2.9 meters) in body length.


The diet of Steller Sea Lions consists of a variety of fish that can be found along the Pacific coast, particularly schooling fish. They are skilled predators, feeding on cephalopods and occasionally venturing into the mouths of rivers to feed on freshwater fish like sturgeon. They will occasionally take sea otter and seal pups, and are themselves preyed upon only by orcas and great white sharks.


Breeding season for Steller Sea Lions takes place in May, in remote and oft-used rookeries. Males arrive first to establish their territories and wait for the females. Unlike other pinnipeds, the males do not attempt to corral the females into harems, but merely protect their own patch of the rookery, allowing the females to wander in and out of the boundaries at will. First, however, the females will give birth to the pups conceived during the previous year's mating season. They will nurse the pups for a week straight, and then begin making hunting trips to sustain themselves, gradually extending the length of the trips until the time comes for both adults and pups to leave the rookery.


Since the 1970s, the populations of Steller Sea Lions along the Aleutian Islands have declined by 70 to 80%, putting the western populations of Steller Sea Lions on the Endangered Species List until 2013. The cause of this decline is the subject of study and debate among researchers - some cite the effects of commercial fishing, in prey reduction and bycatch deaths. Other hypotheses include disease, pollution and increased predation by orcas, and still others state that changes in climate affected the populations of fish, resulting in more low-energy fish like pollock instead of fatty capelin and herring.

Source for all images used in this post.

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