So she was in a box. The box was on the deck of an inflatable motorboat. She scrabbled her paws against the box floor and walls.

“We’ll see how this goes,” Karl Mayer said.

It was a late summer morning, and Mayer and his colleague Sandrine Hazan were animal care specialists with California’s Monterey Bay Aquarium, the gray structure receding in the fog as Mayer gunned the boat into deeper waters. Inside the aquarium, a crowd was already forming around the glass-walled sea otter tank; from the perspective of the tank’s residents, the human species must sometimes appear as one endless lineup of goofy smiles and raised cell phones. A couple of undulating laps, a little nose-rubbing with the paws, a quick session of Bang Plastic Ball Against Rocks—everything seems to provide extreme amusement for the bipeds on the other side of the glass. Pop a whiskery head out of the water and pick a couple of gawkers to flirt with: happy mayhem, guaranteed.

There are semi-rational explanations for people’s ardor at the sight of sea otters, and you can hear experts tick them off: 1. Sea otters are tool users; they pick up appropriately shaped stones, roll over, and position the stones on their stomachs as shellfish-smashing devices. 2. They’re among the world’s smallest marine mammals, and they swim on their backs, which is weirdly entertaining to watch. 3. Something about their faces, the fur, a furry little animal being graceful in the sea …

And here the experts tend to give up, yielding to the obvious. “When people ask me about them, I have to be very professional, with my game face on,” Hazan told me. “But when no one’s around, we definitely use the c-word.” Cute, she means. So relentless is sea otter cuteness that people who work all day with them, while not immune to it, can find it exasperating. The notion that wild sea otters hold each other’s paws, for example, to keep from drifting apart: Winsome but wrong. (Sorry.) Some years ago, two sea otters at an aquarium were photographed floating paw in paw; those images have kept up a robust internet presence, but there’s no reliable evidence that sea otters regularly do this in open water. It is true that they hug their pups while swimming on their backs. It is also true that they sometimes converge into “rafts,” giving the impression of companions gathered for a pleasant group float.

Sea otters can be ferocious, though. They’re predators: carnivorous and tough. They have jaws and teeth that crush clamshells and rip the guts out of spiky littler animals. Their near-extinction story is a brutal eco-drama that commences in the 1700s, when Russian sailors exploring the Aleutian Islands learned what Indigenous Pacific coastal people already knew: Sea otters are covered with the thickest, most luxuriant fur in the world. The coastal people also prized those pelts, but they hunted at an otter-sustaining pace; the new hunters possessed no such wisdom. By 1911, when a treaty curtailed the international seal and sea otter fur trade, a few sparse clusters were all that remained of the sea otter population that had once ringed the Pacific—between 150,000 and 300,000, from Baja California in Mexico up into the northern islands off Alaska, Russia, and Japan.

Now, in waters off the North American continent, a different kind of human intervention has been helping sea otters survive and spread once again. Are they thriving? Touchy question. Is this a happy ending? Touchier question. What about the latest ideas for hurrying that spread along—reintroducing sea otters to more places they once inhabited, like San Francisco Bay? Raise that question among debating partisans, especially people who make their living catching the shellfish that multiplied when no sea otters were around to eat them, and, well, brace yourself. It’s complicated, figuring out how tough, carnivorous predators fit into a world that changed while they were gone, and amid this collision of opinions about Enhydra lutris there was something comforting about the precision of the morning’s task: Help otter 820 get safely back to sea.

Mayer quieted the engine, studying the gray-green water. The rescue sea otters at the Monterey aquarium are numbered rather than named, to keep sentiment in check; the plan is to return them, if possible, to the wild. Otter 820 arrived at the facility’s intensive care unit—someone phoned in a beached-pup sighting; rescuers drove out to scoop her up—between otters 819 and 821. Today’s try at releasing her was a second attempt, as a few months earlier she’d failed the first: Mayer and Hazan transmitter-tracked her as she wandered about, ate too little, kept losing weight. When they finally brought her back in, she was so wasted she slumped without protest into their net.

“We restored her to normal weight and health,” Mayer said. “Now we’re trying again.” He nodded at Hazan, who pushed 820’s box to the edge of the motorboat, tipped it down, and threw open the door.

A newborn sea otter weighs about five pounds, resembles a fur pillow with eyeballs, and for the next few months needs a mother for everything—not just food but also the most basic instruction in staying alive. The adult males don’t stick around to help, and the pups don’t instinctively understand how to grab shellfish off the seabed, crack open a crab’s back, or stash smashing stones under their armpits as they swim. They have to be shown how to groom constantly, fluffing their coats and blowing air into the underfur; sea otters have no blubber, and the famous fur is a thick insulation system for keeping them warm in the water, where they spend most of their time. In the Pacific a sea otter with matted fur or skin wounds can quickly freeze to death.

The Monterey Bay Aquarium has been experimenting with sea otter recovery ever since it opened in 1984, with its focus on the region’s marine life. Some of the last surviving sea otters off California lived not far from Monterey; scientists call these southern sea otters, to distinguish them from the northerns near and above the Canadian border. Before long, reports of injured or stranded southerns set in motion a remarkable sequence of rescue and rehab at the new aquarium. In-house veterinarians performed emergency otter surgery. One area, closed to the public, became a sea otter neonatal ward.

Then, because even healthy pups still had to learn how to grow up, staff members began stepping in as substitute mothers. Mayer no longer works at the aquarium, but during his early years there as an animal scientist, his duties included some all-nighters on the aquarium’s sea otter waterbed, soothing and bottle-feeding an anxious pup. He would carry a pup into the bay with him, a weight belt over his wet suit, and demonstrate diving for shellfish while his pupil watched from above. He used his teeth to crack the shells of live crabs—more parental-style demonstration—while floating on his back. He put shells on his chest and pounded them with rocks.

“We’d essentially model what it was to be a sea otter,” Mayer says. “They’d follow you around. You couldn’t lose your sea otter pup if you wanted to.”

Trial and error taught the humans too. Wild sea otters must not associate the sight and smell of people with comfort or food, so the bottle-feeders improvised what they called Darth Vader disguises: black mask, gloves, dark poncho to alter the human shape. Eventually, to minimize even more the contact between pups and people, the aquarium’s biologists decided to try having the resident adult female sea otters take over the motherly finishing school. These were rescues that for various reasons had been declared unsuitable for release back into the wild but might still intuitively understand what to do—how to foster a pup, teach it to forage and stay warm, prepare it for meeting others in the sea.

No aquarium had ever tried such a thing. But the first of the surrogate mothers (as the biologists labeled them) inspected their new charges, clearly grasped the task at hand, and got to work. That was more than 20 years ago. The population of southern sea otters is currently estimated at about 3,000, an encouraging if still modest advance toward true recovery; they are scattered up and down the middle third of California’s coast, with 100 to 150 living in the protected Monterey Bay slough the aquarium has used as a prime release spot. Wild sea otters now share that inlet with surrogate-raised sea otters and their descendants, all of which seem to have figured out how to yank crabs and clams from the mucky bottom. Where smashing rocks are scarce, they improvise by using empty clamshells or by bashing hard-shelled prey against boat hulls and dock pilings. They’re surviving. They’re raising their young. They’re satisfying their prodigious appetites.

And here, problematically, is the 21st-century sea otter conundrum: their appetites.

Sea otters eat a lot. The daily intake of an adult sea otter can weigh about a quarter what the otter weighs; lactating mothers need even more. They eat shellfish, and the about-a-quarter calculation doesn’t include the shells. (For one 60-pound adult sea otter, picture about 15 pounds of shellfish meat.) Within their Pacific surroundings, sea otters are a keystone species, the term biologists use for animals or plants that are especially important to the ecosystems in which they live. Those giant otter appetites, plus their choice of prey, can maintain—or restore—a healthy equilibrium in their part of the sea.

Among the shellfish sea otters eat, for instance, are urchins. Urchins eat kelp, so without the otters around to hold their numbers down, grazing urchins can take down whole forests of kelp. And scientists are learning that kelp forests, along with seagrasses that flourish when sea otters are present, play their own crucial roles in marine resilience. Kelp tangles make protective nurseries for baby finfish, increasing the number and variety of adult fish. Seagrasses filter out water contaminants and lock carbon into the sediment.

“Sea otters have huge effects,” says research ecologist Tim Tinker, a University of California, Santa Cruz adjunct professor who is one of the world’s leading sea otter experts and has spent decades studying both the northern and southern populations. “That’s why understanding them is so important. When they’re removed from an ecosystem or put back into an ecosystem, everything changes. And that’s disruptive. Some people are going to like the effects they have. And some people are not.”

Case in point: commercial shellfish harvesters. “Like setting off a nuclear bomb,” a dive fisherman named Jeremy Leighton told me one afternoon in a waterfront café, describing seabeds he’s seen in the wake of hungry-sea-otter foraging. “Everything getting wiped out, in a radius, as they expand.”

Leighton lives in Ketchikan, Alaska. He was born in Alaska, as were his father and grandmother. His catch includes geoduck, a large, burrowing clam, and sea cucumber, another shellfish. His territory is Southeast Alaska, currently the global epicenter of people hostile to sea otters. It was here that I heard them described as “an infestation” (a Haida tribal leader) and “a disaster” (a commercial crabber, glaring at the water off his boat). Also this, from a man who’s fished the area for almost 40 years: “Actually one of the most destructive things on the planet.”

To be fair, that last description was prefaced by “cute and fuzzy and cuddly and all that stuff, but actually …” The speaker was Ed Hansen, who works with a group called the Southeast Alaska Fishermen’s Alliance; his wife, Kathy, is executive director. They appreciate the popular appeal, in other words. But their version of the modern sea otter story is one of good intentions gone awry—because unlike their southern relatives, northern sea otters in recent decades have multiplied prolifically in waters from which they had once vanished. A 2021 U.S. Fish and Wildlife Service–supported study put the Southeast Alaska count at more than 27,000 sea otters. Canadian scientists estimate that another 8,000 live along British Columbia’s coast.

Why the huge difference in comeback numbers, northerns versus southerns? The reasons start with human intervention more than a half century ago, when the U.S. government was holding underground nuclear tests on Amchitka Island, a thousand miles west of mainland Alaska. Amchitka is part of the Aleutians, and although that’s the very archipelago where the hunt to near extinction began, by the mid-1960s, some of the world’s remaining wild sea otters could still be found there—remnant colonies, biologists called them. After shock waves from the first test blast in 1965 killed hundreds of these otters, Alaska Department of Fish and Game officials began an extraordinary series of relocation airlifts: Over the next seven years more than 700 sea otters were pulled from the Aleutians and Prince William Sound, flown east, and lowered into the water in ancestral Pacific Northwest sea otter territory.

The otters released off Oregon didn’t make it; by 1981, they’d scattered or died. The otters put in off Washington State hung in along one stretch of coastal waters, their numbers growing steadily but slowly. In Southeast Alaska and British Columbia, though, the relocators set sea otters into the coastline’s multiple bays and inlets, which turned out to be ideal protected settings for rapid—some Alaskans would say explosive—population growth. The females had pups (seven to 10 in a lifetime is typical). The pups grew up and had pups. The expanding colonies moved into more bays and inlets, looking for food.

This means that if you’re watching sea otters eat your family’s livelihood, the MMPA says there’s nothing you can do about it, Alaska Native or not. (Canada has similar prohibitions, but with no exemptions for its Indigenous First Nations.) “The MMPA wasn’t written for ever dealing with overabundance,” says Mike Miller, a Sitka Tribal Council member who chairs Alaska’s Indigenous People’s Council for Marine Mammals. “But if you look at their overall impact on ocean health, there’s a positive side to otters too. There’s got to be something close to balance someplace.”

“Otters are smart,” Miller says. “We didn’t have to take them all out.” Tribal knowledge and scholarly research support the idea that sea otters learn to recognize and avoid danger areas and that Indigenous people may have once used site-specific sea otter hunting to protect designated shellfish areas. There’s no question that they did live amid an abundance of shellfish and sea otters—long ago, to be sure, before there was refrigerated transport plus a global appetite for the animals that sea otters eat. Now Miller is part of an ongoing meeting of Southeast Alaska “sea otter stakeholders,” as they label themselves—fish and game officials, tribal members, scientists, and commercial fishermen—all trying to work out a modern plan for sharing resources with a keystone animal that humans came so close to wiping out.

No specific proposals have emerged from the Alaska discussions, but there are people watching closely from the western edge of the lower 48, especially around San Francisco Bay and the Oregon coast. Both regions are under serious study as reintroduction sites—shellfish-rich waters that once supported thousands of sea otters and could perhaps do so again. And in both places, healthy sea otter colonies might improve the water quality and plant life while delighting tourists.

The local dive industry and crab fisheries’ wary response: We’re part of the ecosystem too. “We are not necessarily dead set against sea otter reintroduction,” says Oregon Dungeness Crab Commission executive director Tim Novotny, who has joined ongoing talks with the Elakha Alliance, a group of conservationists, scientists, coastal experts, and tribal leaders exploring another attempt at returning sea otters to the state. “The concern is, you don’t want to put a floating time bomb of furry crab-eaters in the water. Goats are cute, but nobody wants 5,000 of them in their backyard.”

Elakha is a Chinook word for “sea otter,” and the alliance’s president, a former Oregon coastal planner named Robert Bailey, says he and his colleagues are working hard to learn from the Alaska experience—to regard sea otters as “everybody’s treasures,” as he puts it, while trying to craft reintroduction proposals that might keep human shellfish harvesters from losing too much of their catch. In any case, the sea otters would have to be placed strategically, Bailey says, and their population monitored closely. “We want to minimize that impact,” he adds.

Where might these sea otter transplants come from? Among other sources, the populations that include surrogate-raised otters like 820. A carefully monitored reintroduction site could become another release spot for the Monterey Bay Aquarium’s rescue sea otters, and two other West Coast aquariums are developing Monterey-style programs to pair surrogate sea otter mothers with rescue pups. Those programs will need appropriate release spots too.

And here it would be nice to be able to report that 820 was last observed swimming serenely in Monterey Bay, smashing crabs on her stomach and so forth. Alas, that’s not what happened. In the tradition of her species, 820’s story turned into a just barely survival saga: A few weeks after that second release, she slid onto a nearby dock, wounded and emaciated. She’d been bitten by a shark. She had parasites. Rescuers scooped her up again, the vet staff nursed her back to health again, and this time 820 was formally pronounced unsuited to life in the wild. She lives these days in a rock-landscaped outdoor pool at SeaWorld San Diego, where she and her poolmates—all rescue sea otters, like 820—“hit it off,” says Shirley Hill, an animal care specialist who’s worked for decades with sea otters. “She’s just got a great disposition.”