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She sees sea otters by the nearshore: Tracking sea otter populations with Dr. Shawn Larson

Seattle Aquarium Nerdy Science Series logo of an illustrated microscope.

This story is part of our Nerdy Science Series—how we’re using research and technology in service of a healthy ocean.

Guests at the Seattle Aquarium know how fun it is to watch sea otters eat and play. But for sea otter researchers, watching these adorable animals on Washington’s outer coast also provides valuable scientific information. By keeping track of wild sea otter populations through regular surveys, Dr. Shawn Larson of the Seattle Aquarium and her team hope to better understand the important role otters play in the marine ecosystem and what the future might hold for them.

Dr. Shawn Larson standing on a rocky shore and holding a small telescope.
Senior Conservation Research Manager Dr. Shawn Larson studies wild sea otter populations and diets.

Searching for sea otters on Washington’s outer coast

Each June for the past 23 years, Seattle Aquarium researchers have participated in a statewide, multiday survey of the Washington sea otter population, organized by the U.S. Fish and Wildlife Service and the Washington State Department of Fish and Wildlife.

Shawn and other Seattle Aquarium staff assist by forming ground teams at specific locations along the coast to carefully count all the otters in an area. The team usually leaves bright and early to hike to the observation point, where they set up their spotting scopes and start looking for otters.

Three researchers observing sea otters on a beach; three of the researchers are holding binoculars up to their eyes.
Researchers from the Seattle Aquarium and Oregon Coast Aquarium look for sea otters off the Washington coast.

They also record information on the otters’ ages and behaviors. During the survey, a plane circles above large groups of otters—known as rafts—to take high-quality digital photographs. Researchers count the otters in these photos later.

The otters tend to float about a kilometer (a little over half a mile) from the shore in groups of up to 1,000. It can be hard, at that distance, to distinguish rafts from clumps of kelp floating nearby. But Shawn, a seasoned otter spotter, knows to look for heads and flippers. Otters also tend to appear black, while kelp looks dark brown.

A sea otter floating on its back in the ocean.
A sea otter floating off Washington’s outer coast.

The Seattle Aquarium also does surveys of the local population monthly, documenting their numbers and diets. Like us, otters have preferred foods. If they’re available, otters will go for sea urchins, crabs and clams. When those become scarce, otters will turn to snails, mussels and sea cucumbers. Shawn has even seen otters eat a giant Pacific octopus!

“Their diet starts to diversify…and that’s when we know that their population has pretty much reached its carrying capacity—meaning the limit for that area,” Shawn says.

Happily, the sea otters in Washington are doing well. Their population is steadily growing with an increase of about 10% each year. They’re growing large and raising many pups, suggesting that these days, there’s plenty of their favorite foods on the outer coast.

Scientists still have a lot of questions about sea otters

Despite decades of research, scientists are still uncovering new information about sea otters. We know that otters eat sea urchins that would otherwise consume kelp. So, where there are otters, there are usually also healthy kelp forests, which serve as habitats for an array of nearshore marine life. However, researchers seek a deeper understanding of how sea otters impact nearshore environments.

"They're kind of a mystery in a lot of ways. There's a lot we do know about them, but there's a lot we don’t."

“We know that sea otters tend to structure the nearshore where they live, but exactly how does that work? What are the pieces of the puzzle that make it work?” Shawn says.

To unravel the mystery, the Aquarium is in the early stages of using a remotely operated vehicle, or ROV, to study otter foraging behavior in kelp forests on the outer coast. By going underwater to where the action is, the ROV will provide in-depth footage and data on sea otter foraging behavior.

A better understanding of sea otters and kelp can’t come soon enough. Kelp is highly effective at sequestering carbon, which could help offset some effects of climate change.

"I hope that we continue to do this work for decades to come… The food sea otters are able to catch really will show how they are able to adapt or not to oceanic changes."

Another question researchers are exploring is how sea otters will react to climate change.

With up to 1 million hairs per square inch, their dense coats keep them warm in the chilly waters of the Pacific. But otters have trouble expelling heat. Rising ocean temperatures could push them farther north. At the same time, otters tend to thrive in nearshore environments. Rising sea levels and melting sea ice could provide more habitat for them.

“We just don’t know. There could be dramatic negatives with climate change for sea otters and there could be dramatic positives,” Shawn says.

Two researchers stand on a beach overlooking the ocean searching for sea otters.
Researchers Katie Shelledy from the Seattle Aquarium, left, and Brittany Blades from the Oregon Coast Aquarium search for sea otters.

How to help sea otters in the wild

One thing we do know is that sea otters need a clean home. Trash that ends up in the sea can reach them via ocean currents. By properly disposing of trash, you can help keep the ocean clean for sea otters and other marine life.

Consider reducing plastic consumption and choosing reusable options when you can. Better yet, volunteer at a beach cleanup to remove plastic and other trash from our shores. You can even get your friends involved!

For more ways to help the ocean and all that depend on it (including humans!) check out our Act for the Ocean page.

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Please note: Our ticketing and membership systems will be offline for approximately two hours starting at 9pm Pacific on Tuesday, February 20. During the maintenance window, online ticketing and membership will not be available.

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Two sea otters at the Seattle Aquarium floating on the water in their habitat, holding onto each other demonstrating a rafting behavior.

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An adult sea otter at the Seattle Aquarium looking upwards with its front paws resting on its front.

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Sea otter at the Seattle Aquarium laying on its back, raising its head and front paws.

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