Otariidae

Sea lions

Stellar sea lions.
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There are six extant and one extinct species of Sea Lions; the Steller Sea Lion, Australian Sea Lion, South American Sea Lion, New Zealand Sea Lion, California Sea Lion, Galápagos Sea Lion, Japanese Sea Lion (extinct). These occupy a large range of habitats in both the Northern and Southern hemispheres.

The Steller Sea Lion (Eumetopias jubatus) is found in the Northern hemisphere, abundant in the North Pacific coasts from Hokkaido to the Southern waters of California. Breeding colonies can be found can also be found on many different islands such as Ion and Yamskiye in the Northern sea of Okhostk and in the Gulf of Kronotski on the Eastern coast of Kamchatka. It has been observed that the Steller Sea Lion moves slightly southward during the summer months. They are the third largest of the Pinnipeds after the Elephant Seals and the Walrus, with males weighing around one tonne and over 3m long. Females are much smaller at just 270 kilograms. The Steller Sea Lion is able to dive up to depths of 180m but only does so for a couple of minutes at a time. They tend to feed over night, feasting on a wide range of fish as well as shrimp and squid. Like the Elephant Seal, the Stellar Sea Lion does not drink as they get all the water they require from their food.

The Steller Sea Lion becomes sexually mature at around three- seven years old. Breeding season is normally in May to June, with males arriving first to gain their territories. When the females arrive, up to three weeks later, they are arranged into harems of around 10- 20 cows. When the pups are born they weigh around 20 kilograms and have a thick grey brown coat which changes to a dark brown before the lighter brown of the adult sea lion. Lactation has been known to last for over a year, sometimes for as long as three years. Like most other Pinnipeds, mating takes place shortly after the females have given birth and the gestation period is roughly 11.5 months (including delayed implantation).

The South American Seal Lion (Otaria flavescens) can be found in the Southern hemisphere on both the Atlantic and Pacific coasts of South America. They are much smaller than the Steller Sea Lion with males at around 2.5m and weighing up to 300 kilograms. They are able to dive up to around 150m deep but normally feed in shallower waters than that. They normally feed on squid and crustaceans as well as fish and occasionally penguins.

Pups are usually born from mid December to mid January. Although unlike many other families, mating occurs before this, between August and December. Mothers stay with their pups for one week before heading back to sea. They return once a week to nurse their pups for sometimes up to a year, when their next pup is born. When the females are at sea the pups gather in groups know as pods and spend most of their time playing or sleeping. Males are extremely dominant and protective of their females. Usually there are around nine females in a harem which is closely monitored by the harem bull. Younger males who did not manage to get a harem remain close by and sometimes challenge the harem bull. This causes distress within the harem as mothers are often split up from their young and pups are sometimes squashed.

Fur Seals:

There are nine species of Fur seals, one of which (the Northern Fur seal, Callorhinus ursinus) can be found in the Northern hemisphere while the rest are found in the Southern. Unfortunately their characteristic layer of insulating fur has made them an object of commercial hunting and the production of seal fur coats.

The Pribolof Fur Seal or the Northern Fur seal can be found on islands in the Western and Eastern regions of the Bering Sea as well as on Robben Island off Sakhalim. The Pribolof Fur seal is known to migrate south down the Japanese and North American coasts, returning to the summer months to breed. Migration begins in October although many leave in November. The Pribilof Fur seal exhibits strong sexual dimorphism, with males being up to 4.5 times heavier than females (270:60 kilograms, male to female ratio). Males have coarse hair, particularly on their neck which is thick and wide. Their heads appear small because of their short, vibrissae covered muzzle. They have been recorded diving at depths of 73m to feed. They commonly feed on squid and a range of fish including salmon and herring.

Norther fur seal bull.
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Females usually give birth between mid June and mid July. When born, the pups are around 60cm in length and weigh about 5 kilograms. Similar to the Sea Lion, mothers remain with their pups for the first week before they head back to sea, only retuning once a week to nurse their pups. For the rest of the time, all the pups group together into pods and spend their time sleeping and playing. Although they are able to swim at birth they do not normally head into the water until they are over a month old. Males reach sexual maturity at five years old but do not become sexually active until they are eight at the earliest. This depends on if they are able to get harem bull status which may not be possible until they are as old as 12. Females however, are able to have their first pup when they are just four years old. Males arrive at the rookery in early June before the females to establish their territories by roaring and fighting. They then do not return to the water or feeding for a period of up to 2 months. A harem has, on average, around 50 females. Mating begins around a week after the females have given birth and the gestation period lasts for about a year, including a 3.5- 4 month delayed blastocyst implantation stage.