Blog Post Jennifer Errick May 26, 2021

Otterly Irresistible Park Wildlife

In honor of World Otter Day, here are 7 facts you may not know about these charismatic mammals and where you can find them in the National Park System.

1. Two distinct types of otter live in the United States.

Otters live around the world, on every continent except Antarctica and Australia. Of the 13 otter species, only two are found in the United States — the sea otter and the North American river otter. Both live in U.S. national parks, but in the different habitats their names suggest. Sea otters weigh about 45 to 100 pounds and live in the Pacific Ocean, and the considerably smaller river otters weigh 10 to 30 pounds and swim their way through a variety of freshwater habitats (including — but not exclusively — rivers).


2. Sea otters have the thickest fur of any animal, which once led to deadly consequences.

Otters lack blubber and rely on their dense coats to keep them warm. Their fur can contain up to a million individual hairs per square inch, making it luxuriously plush — and a historical target for hunters, who once killed so many of these marine mammals, they nearly went extinct. There were just a few hundred sea otters left in 1911 when an international treaty outlawed hunting them. Their populations have since rebounded, and reintroduction efforts at Glacier Bay National Park and Preserve have been an important part of their recovery.


3. Otters are voracious eaters and skilled foragers.

River otters eat roughly 15% to 20% of their total body weight in food each day, and sea otters have even higher metabolisms, eating about 25% to 30% of their weight. Fish is the most common food for both species, but these cunning predators will feed on many other kinds of animals, from crabs and crayfish to frogs and salamanders. A river otter’s pronounced whiskers help it sense prey in deep water, and it has even been known to feed on waterfowl and beavers. Sea otters, meanwhile, are one of relatively few animals that use tools — pounding on the shells of crustaceans with rocks to eat them.


4. When otters get together … it’s a romp.

Etymologists believe that the word “otter” is derived from the same root as the word “water.” The collective noun for a group of otters is a bevy, a lodge or a romp. And when they’re in the water, a group of otters is a raft.


5. A river otter once became a local celebrity at a California park — until he got lonely.

In 2012, San Franciscans went gaga over Sutro Sam, the first otter residents had seen in their city in 50 years. Sam took up residence at a freshwater pond near the Sutro Baths, the ruins of a large late-1800s-era swimming pool that is now part of Golden Gate National Recreation Area. Though the public pool is long gone, Sam happily frolicked, chomped on fish and posed for park-goers — who flocked to the park to see him. Sadly, in early 2013, Sam left as abruptly as he arrived — at the beginning of mating season — leading many to speculate that he was looking for companionship beyond what his many human fans could offer.


6. Sea otters improve their habitats.

Sea otters are a keystone species in the coastal areas where they live, meaning they have a significant effect on their environment relative to other species. One important positive effect sea otters have is to unleash their voracious appetites on sea urchins, which helps reduce the grazing and pressure on kelp forests, improving underwater health and resulting in a more diverse ecosystem overall. Kelp also helps to absorb and sequester carbon dioxide, meaning these otters even do their part, indirectly, to reduce a major contributor to climate change.


7. Otters are wild. Give them space.

Otters are so cute, it’s tempting to forget about wildlife safety when there’s one nearby, but the National Park Service rule of thumb to leave at least 25 yards between yourself and wild animals (100 yards with larger predators such as bears and bison) still applies. Otters have sharp claws and teeth, can carry diseases such as rabies, and will sometimes become territorial, especially when guarding their young. A visitor swimming in Manzanita Lake at Lassen National Park was bitten by a river otter last year when he unknowingly got too close to its three babies, and though the injuries were not thought to be life-threatening, they were significant enough to require hospitalization.


Where to see them

  • River otters live in a variety of freshwater environments throughout the United States. Yellowstone is an ideal place to spot them, though they can be found in parks as diverse as Big Thicket National Preserve in Texas, Congaree National Park in South Carolina, Isle Royale National Park in Michigan, Cuyahoga Valley National Park in Ohio, and Mississippi National River and Recreation Area in Minnesota (which even has its own Otter Cam).

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  • Sea otters only live in coastal areas of the Pacific Ocean, and their biggest populations are in Alaska at places such as Glacier Bay National Park and Preserve and Kenai Fjords National Park, though they also live farther south and can be spotted at other West Coast parks, including Channel Islands National Park in California and Olympic National Park in Washington.

About the author

  • Jennifer Errick Managing Editor of Online Communications

    Jennifer co-produces NPCA's podcast, The Secret Lives of Parks, and writes and edits a wide variety of online content. She has won multiple awards for her audio storytelling.

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