What Otter Is This?

Otters are terribly cute little critters. There are several species worldwide, but in North America we have the river otter and the sea otter. Other than one living in a river and one living in the sea, what are the differences? If you should happen to see an otter near the coast, how do you know which one it is?

It might seem silly to not know what otter you are looking at, but coastal river otters will swim into the ocean. Now that you can’t always rely on the type of water to tell the otters apart, what do you do?

You probably won’t have the two otters side by side for a comparison, but the sea otter is much larger, twice or even three times the size of the river otter. The sea otter’s tail is shorter and flatter, while the river otter’s tail is about half the length of its body. River otters have a more rounded nose than sea otters, and the river otter’s nose farther above the mouth. The sea otter’s nose is slightly pointed at the top and the bottom comes to the mouth much like a cat’s. The sea otter has very dense fur, which is why they were hunted to near extinction. The river otter has a course fur and a layer of fat.

Sea otters at sea (Marine Mammal Commission)

River otter swimming

Movement is a good indicator of which otter you’re looking at. Sea otters swim almost exclusively on their backs, using their bellies as a dinner table. River otters swim on their bellies (riding very low in the water) and usually eat on land. On land, river otters move quite well, running with an arched back or sliding downhill on snow. Sea otters rarely come ashore, and when they do, they are clumsy critters that waddle more than they walk.

Sea otter ashore (Oregon Zoo)

River otter on land (Smithsonian National Zoo)

Hopefully you will be lucky enough to find yourself in a position that you see an otter and wonder what kind it is. Sea otters live exclusively on the West Coast and are a threatened species so you will be lucky indeed to find one. River otters have suffered in the past due to hunting and trapping pressures just as their seafaring cousins, but have had a more successful recovery thus far and enjoy no special federal protection.

So you’re far more likely to see a river otter based on population and range. Still, seeing a river otter is a special event. I’ve come across them in the wild twice, and both times it was an unexpected delight. The first otter was in my pond while I was surveying amphibian egg masses. The second was in Capitol Lake in Olympia, WA where I was joining a group for an evening bat program. Check your local waterways; you may be in for a pleasant surprise too!

This week's otter information comes from the Seattle Aquarium. Don't forget to follow Nature Minute on Facebook!