This story contains graphic descriptions and depictions of carnivory.
It’s a sleepy, sunny July day in the meandering wetlands of Elkhorn Slough, outside of Moss Landing in Monterey Bay, and a gaggle of eco-tourists is about to get a classic introduction to the iconic California sea otter (Enhydra lutris nereis). Captain Joey Rodrigues of Monterey Bay Eco Tours maneuvers El Cat, a 37-foot electric catamaran, to get us all a good view of these charismatic megafauna incarnate. They are, of course, furry and photogenic, with adorable mannerisms and an inspiring story of rebounding from near-extinction during the 18th and 19th century fur trade. Famously, they act as keystone species in kelp forests and wetlands, by consuming marine invertebrates like urchins and crabs. But not every sea otter has gotten that memo.
“Hey, what’s that on its belly?” someone asks.
It’s not the world’s largest clam.
“Oh wow—she’s got a bird!”
As the sea otter’s powerful clam-crushing jaws take another bite of a common loon, its fuzzy facade of cuteness is plucked away, feather by feather.
“Yep, that’s her spot,” says Rodrigues. We have just become the latest witnesses to an innovative sea otter some locals are calling “The Birderer.”
Even with decades of high-profile research into their behaviors, sea otters can still surprise us.
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This behavior isn’t totally new, though. Sea otters are mustelids—the greater weasel family—which are no strangers to murder most fowl. Among minks, ferrets, weasels, fishers, stoats, otters and kin, the trend seems to be that the more aquatic the animal, the fewer birds are on the menu. Recently, river otters in San Francisco made the news by taking down brown pelicans. In the 1980s, a string of serial birderer male sea otters chowed on surf scoters, grebes, cormorants, loons and gulls around the Monterey Peninsula. Now, some four decades later, biologists and other frequent slough-watchers say that it seems an avian foodie movement has been brewing once again in the slough.
“I have seen otters mainly interacting with seabirds—wrestling, carrying, etc—and occasionally eating them,” says Michelle Steadler, a sea otter biologist of more than 40 years, formerly with Monterey Bay Aquarium and now with UC Santa Cruz and the Wildlife Conservation Network. “It could be a learned behavior from the mother. It could be in response to resource limitation,” she says. “Or just certain individuals having a penchant for birds.”
Sofie Scanlon, a naturalist with the Elkhorn Slough Foundation and Monterey Bay Eco Tours, says she’s seen the behavior at least 10 times in the past year of weekly tours. Recalling one sighting, she says, “I watched the sea otter rolling around with this large body on its chest. Then a wing popped up.” Scanlon and her colleagues are working alongside scientists at the U.S. Fish and Wildlife Service to document this otter chaos.
Local naturalists say they started to see the behavior between 2022 and 2023. Sightings at Birderer Bend (as I’m calling it) seem to be on the rise, often involving one specific individual. By the Woodward Marine Fuel Dock, near The Sunflower Star Laboratory, another otter has been seen sampling cormorants in the past year.
She’s been dubbed “Birdadette.”
Steadler says she suspects just a few individuals are hunting birds, including one tagged adult female who has been seen opportunistically taking cormorants and one untagged subadult female (the Birderer). “I would say in general it’s rare, but there happens to be an individual otter or two that have taken an interest in birds in a high-visibility area.”
“Right now because it’s in the slough where there are daily boat tours, many, many kayaks, and scientists and volunteers all watching otters, it seems like a lot right now,” Steadler says.
Elkhorn Slough is California’s second largest estuary after San Francisco Bay, and a popular destination for watercraft and wildlife alike. Harbor seals use it as a habitual haulout and pupping ground, lining the muddy banks like so many unbothered tailgates of sea sausages. It’s also a birder’s paradise, with more than 300 species of birds taking advantage of a rare surviving wetland and its roadside services either for a migratory pit stop or as permanent residents. It’s become a sanctuary for California sea otters, with a furry flotilla of nearly 100 animals—many of them alumni or descendants of rescued and released sea otters from the Monterey Bay Aquarium’s otter rehabilitation program.
As their populations rebounded in the 1970s and 80s, their impact on the surrounding environment made them the poster child for the concept of the “keystone species.” Sea otters are the smallest marine mammal in these Pacific waters and depend on the world’s densest fur to keep warm in the absence of blubber. Their fiery internal furnace is also fed at a furious pace: Sea otters need to consume 20–25 percent of their weight in food every day, more if they are mothers. Historically, this has been observed to be largely foraged from marine invertebrates— over 100 species across their range. Because of their insatiable appetites, sea otters fundamentally restructure the biological community around them, with cascading consequences. Famously, in certain circumstances, sea otters can suppress sea urchin populations, promoting kelp forest growth.
In Elkhorn Slough, their gardener mythos has grown even greater, as the reestablished otter population has aided wetland restoration. By eating crabs, which eat sea slugs that eat algae growing on eelgrass, more otters has meant more verdant pastures for many species, including seabirds—well, minus one or two.
Just as the gasps have subsided onboard El Cat, we hear a splash, and our protagonist disappears in a ripple. Just then, a double-crested cormorant appears to dive rear-first into the slough—a first for all seabirds. Moments later, the cormorant reemerges, with fangs in its neck. The otter has gone for a second course.
As a culture, we love a good story, and our idols to follow a family-friendly script. But we know now that there are at least a couple of sea otters that are refusing to be pigeonholed.
