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Pinnipednesday - Callorhinus ursinus Edition

Been a long day today. How about we all wind down by learning about pinnipeds?

The Northern Fur Seal (Callorhinus ursinus) is the largest of all fur seal species, and can be found in the Bering Sea, the Sea of Okhotsk and the northern Pacific Ocean. They have long, flexible flippers that enable it to move relatively quickly on land and with extreme ease and agility in the water. They are even able to rotate their hind flippers to face forward. They have been hunted as a food staple by the indigenous peoples within their range for thousands of years.


Sexual dimorphism in Northern Fur Seals is extremely pronounced. Adult males can grow up to 7 feet (2.13 meters) in body length and weigh almost 600 pounds (270 kg). Females are much smaller, averaging only 5 feet (1.5 meters) in body length and weighing in at 110 pounds (50 kg). Males have thick, muscular bodies with longer, coarser guard hairs around the neck and shoulders. This mane is usually dark brown or black. Females are typically lighter in color, cream and light brown.

The diet of Northern Fur Seals consists mainly of fish and squid that live in the pelagic zone, including mackerel, herring, pollock, capelin, hake and lantern fish. Northern Fur Seals themselves are hunted by orcas and sharks, and pups can fall prey to Stellar Sea Lions, Arctic Foxes and gulls. Mortality rate among young pups can be quite high because the breeding rookeries are so crowded, and their bodies provide sustenance for many scavengers that inhabit their range.


The pupping and breeding season of Northern Fur Seals usually takes place in June. Males will arrive at the rookeries first to establish territories by fighting among each other. The males who win the breeding rights to a specific group of females are called beachmasters, and will mate with them within a week after they've given birth to the pups conceived the previous year. They do not feed at all during this time, and usually lose up to 20% of their body weight during the breeding season. Females delay the implantation of fertilized eggs for up to four months, in order to time the births to happen at the same time every year. They'll nurse their pups constantly for 10 days, and then will go out to sea to feed themselves, coming back to nurse the pups intermittently. The pups are weaned at four months.


Northern Fur Seals are considered to be vulnerable by the IUCN, because they were heavily hunted in the 18th and 19th centuries. This nearly led to their extinction. Commercial hunting is still banned, but Northern Fur Seals are no longer protected by the treaty that was signed in 1911 to save them from being wiped out. In Canada, hunting is permitted only for indigenous people who rely on the seals for food. But these seals are easily tangled in commercial fishing nets and are vulnerable to the pollution of their habitat by oil spills, and oil and gas exploration.


Source for all images used in this post.

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