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Northern Fur Seals

About AquaFacts: AquaFacts are a resource for students who are looking for information on the animals at the Aquarium or other Aquarium-related topics. Here, we’ve compiled some of the most frequently asked questions that we’ve received about harbour seals. The answers come from our biologists and from reputable sources that we reference at the end of this page. If you have a question about harbour seals that’s not addressed in this page or the references below, please feel free to email our librarian.

Northern Fur Seal

Questions & Answers

What is a fur seal?

Fur seals are a type of Pinniped, related to animals like harbour seals and steller sea lions. Despite their name, fur seals are more closely related to sea lions (members of the earred seal or Otariidae family) meaning that they have obvious external ear flaps and large flippers that support their body upright when on land. Like their cousins, fur seals eat fish and are very good swimmers. They are known for having the second densest fur in the animal kingdom (next to sea otters).

What do Northern fur seals look like?

This species displays sexual dimorphism, meaning that the males and females look different from each other. Mature males develop a thick neck and can weigh upwards of 186 kgs and as long as 2 metres. Females on the other hand stay sleek and slender with a body length of under 1.3 metres and only weighing 40 kgs. Females tend to be a brown or grey colour, while males have a red to black coloured coat.

Where are Northern fur seals found?

The Northern fur seals can be found in the Pacific Ocean with their range extending from Japan, through the Bering Sea (with breeding colonies on the Commander, Pribolof and Bogoslof Islands which lie west of Alaska) and then down to California.  

What do Northern fur seals eat?

Northern fur seals eat herring, sandlance, capelin, anchovy, squid and salmon just to name a few.

How does the Northern fur seal breeding season work?

Males arrive at the breeding sites (typically on the islands in the Aleutian Island chain) one month before the females do to establish their territory. Once the females arrive in mid June they give birth to their young who were conceieved the previous year. About 11 days after birth, females will mate again. Males manage a harem, a group of females that he protects from other males. In order to make sure he doesn't lose any of his potential mates, the male will not eat throughout the breeding time, and have been observed to lose up to 20% of their overall weight. 

The females will nurse their pups for about 10 days before they make their way back to the ocean to feed for roughly a week before returning to nurse their pup for a couple of days. This type of care continues for 4 months before the female returns to sea until the following June. The fertilized egg she currently carries experiences a delayed implantation which makes sure the pup will be born at the right time the next year.

Are Northern fur seal populations endangered?

Yes. The population of Northern fur seals has shown a dramatic decrease since the 1970's. Historically this species was hunted to near extinction for their fur which was highly prized when it was "discovered" by Europeans in the 18th century (the fur seals were relied on by local First Nations peoples as an important resource for many years prior). They have been protected since the early 1900's, but in the 1970's a sharp decline in their population was noticed. Researchers have been trying to understand this change through research both in the field as well as with facilities that house Northern fur seals, like the Vancouver Aquarium.

What is happening to the Northern fur seals?

Researchers believe that the animals do not have access to the right kinds of seafood, and are calling it the Nutritional Stress Hypothesis. Not all seafood is created equal, and some types of fish like herring have more calories than others like pollock. If a fur seal is eating a lot of pollock, they will feel full, but their bodies aren't getting the energy it needs (sort of like if you were to only eat plain popcorn. You would eventually feel full but your body isn't getting the nutrition it needs to get through the day). It is unclear what exactly is causing this shift in food availabilty, but the team of researchers from Canada and the USA are working together to reveal the answer.

Facts & References

Key Facts

  • Male Northern fur seals are called bulls, and females are called cows.
  • Unlike their name implies, fur seals are related to sea lions due to the shape of their body and the presence of external ear flaps. 
  • Northern fur seals spend an incredible amount of time in the ocean and will even sleep while at sea.
  • While their main prey is ocean creatures, fur seals have been observed eating sea birds!


  1. http://www.marinemammal.org/biology/northern-fur-seal/
  2. http://www.arkive.org/northern-fur-seal/callorhinus-ursinus/
  3. http://www.marinemammal.org/biology/northern-fur-seal/diet/
  4. http://www.marinemammalcenter.org/education/marine-mammal-information/classification.html?referrer=http://www.marinemammalcenter.org/education/marine-mammal-information/pinnipeds/?referrer=https://www.google.ca/ 

Permission is granted by the Vancouver Aquarium Marine Science Centre for classroom teachers to make copies for non-commercial use. This permission does not extend to copying for promotional purposes, creating new collective works, or resale.


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