Sleeping river otter
River otters are generally more active at night, so may often be found napping during the day.


What’s better than a whole day devoted to otters? A whole day PLUS a blog post to give you even more reasons to love these irresistibly charming animals! Does anyone feel a top 10 list coming?


  1. There are 13 different otter species in the world (including the northern sea otters and North American river otters that make their homes at the Seattle Aquarium). Many of them are listed as endangered on the IUCN Red List.
  2. Otters are mammals, scientific name Mustelidae, and their size varies by species. The largest species, aptly named the giant otter, can grow to be six feet long and weigh up to 75 pounds!
  3. Otters are found on every continent in the world except Antarctica and, interestingly, Australia. Maybe the kangaroos have beef with them?
  4. While there are many differences between the species, there are also a lot of similarities. Here’s one: no matter the species, otter poop is especially smelly! It’s so stinky it even has its own name: spraints.
  5. Otters are known for their dense fur. In fact, they have the densest fur of any animal in the world, with up to 1 million hairs per square inch of skin (by comparison, the average human has about 100,000 hairs TOTAL on their head).
  6. Sea otters are what’s called a keystone species, which means they hold a unique and essential place in the health and functioning of an ecosystem—and without them the ecosystem would change dramatically. TLDR: sea otters are essential for ecosystem health.
  7. What makes sea otters a keystone species? In short:
    • In the wild, sea otters eat sea urchins (among other things).
    • Sea urchins eat the holdfasts, or roots, that anchor kelp to rocks and rocky substrates.
    • Kelp forests provide homes for many, many marine species.
    • So…if the otters aren’t eating the sea urchins, more urchins are eating kelp holdfasts and there are fewer kelp forests for the animals that rely on them. See how that works?
  8. As we mentioned above, sea otters eat sea urchins—and a lot more! Sea otters need to eat 25% of their body weight EACH AND EVERY DAY to fuel their metabolism, which is extra high because, unlike marine mammals such as harbor seals, they don’t have a blubber layer to stay warm. (That’s like a 100-pound person needing to eat 100 quarter-pound cheeseburgers every single day!)
  9. How do you know if the animal you spotted was a sea otter or a river otter? The short answer is that sea otters are found in the waters of Washington’s outer coast; river otters are found in Puget Sound and often get mistaken for sea otters. Check out our cheat sheet to learn more about the differences between these two species.
  10. Drum roll please…the 10th reason sea otters are so amazing? They’re just so otterly cute! And we’re ready to prove it: check us out on Facebook, Instagram and Twitter today for an otter onslaught. Want to get to know the otters in our care? Take a deep dive into our sea otter and river otter fact sheets. And virtually visit the sea otters with our live webcams!
Sea otter floating
Sea otter Aniak lives at the Aquarium with her mom, Lootas.



Throughout our history, we’ve focused on sea otter research, husbandry and education. (Fast fact: we were the first aquarium in the world to have a sea otter conceived and born in human care—and subsequently live to adulthood.)

Our research efforts increase our knowledge of the animals in our care, contribute to conservation efforts in the wild, support public interest in research, and encourage people to learn, like you’re doing right now! We’re involved in four sea otter research studies: an annual survey, population genetics, ecology and endocrinology.


Every year the Seattle Aquarium participates in the annual Washington sea otter survey, organized and run by the United States Fish and Wildlife Service (USFWS). We’ve participated since 2001 and expanded on this important work by conducting our own sea otter foraging research, including bimonthly surveys, along Washington’s outer coast.

Our research team observes sea otter foraging behavior in the wild to better understand what the otters are eating, the energy they must expend to hunt their prey and the general health and wellbeing of the resident population. By studying our local sea otters, we’re gaining a better understanding of the overall health of the ecosystem and the population levels of other species that sea otters rely on as a source of food.

But spotting sea otters in the wild isn’t as easy as you might think! View the video below and see how many otters you can count.



So…how did you do? It takes patience and a sharp eye to get an accurate count. We have to confess: we don’t know exactly how many sea otters are in that video, either. That’s why the research team uses a variety of resources to confirm their counts. Happy World Otter Day!



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