An Accidental Science Project Reveals How Crucial Sea Otters Are to Kelp Forests

Fur traders exterminated them in Washington. A hydrogen bomb helped restore them. These events have given ecologists startling insight into the power of these kelp forest carnivores.

On a foggy day in mid-September, I go looking for a glimpse of a colossus on the outer edge of Washington State’s Olympic Peninsula, the wildest stretch of coastal wilderness in the Lower 48. Olympic National Park doesn’t much cater to the faint of heart; it’s infamous for its vertiginous headlands and remote beaches where hikers get cut off by rising tides. Fortunately for lilydippers like me, there’s a rare soft opening from Lake Ozette out to the rugged seashore at Cape Alava.

I ditch my car at the Ozette ranger station and, from a rack of pamphlets, pick up the otter equivalent of a baseball card. It profiles the North American league’s only two players—Enhydra lutris and Lontra canadensis—and right away it proves useful. Crossing the footbridge over the idle Ozette River, I flush a pair of otters resting below. They scamper into the water and streak away along the bottom, swimming facedown, paws pulling hard fore and aft, long, tapered tail streaming behind. I consult my card. Agile on land. Check. Swims facedown. Check. Paddles with webbed feet of roughly the same size. Check. Found in freshwater as well as salt. Check. This is Lontra canadensis, the river otter. Common as rain in the Pacific Northwest.

I walk on.

A boardwalk of split cedar slabs angles out to Cape Alava, through towering western hemlock and Sitka spruce, blue huckleberry, bunchberry, and salal. Three miles along it drops sharply. A silvery sea opens ahead and smacks me with its briny tang. Boardwalk gives way to red-brown duff; duff slopes down to gray-brown shingle and sand. Now cue the roar of the ocean. Cue the squeaky-hinge soprano of glaucous-winged gulls. Cue the raucous bellowing of a thousand male sea lions on the Bodelteh Islands offshore. I clamber aboard a titanic drift log and glass the kelp-ruffled slackwater.

Three adult otters loaf belly up in the kelp, riding the glittering sea. They cock their heads forward out of the water and, three feet astern, their flipperish, clown-shoe hind feet, too. Clutching their slender forepaws high on their chests, they look like pious little vicars lying in bathtubs a bit too small.

Checkmate. Here is Enhydra lutris, the sea otter, smallest of marine mammals and the most influential. This is the animal whose luxuriant fur drove Russian then British and American exploration of the Pacific Northwest, fueled the transformation of New England’s economy, and made Alaska Russia’s to sell. Whose appetite for shellfish shapes the kelp forest. Whose presence and then absence, extermination and then unlikely partial restoration to Pacific coastal habitats have given ecologists startling insight into the power of top carnivores. Whose tenuous survival may have stunning implications for the survival of wild species and habitats not only here on this remote coast but everywhere.


Though the sea otter is thought to have evolved some two million years ago, its story doesn’t really pick up until 1742—the year the shipwrecked crew of explorer Vitus Bering’s Russian expedition limped back to Kamchatka in an improvised boat. The crew had survived nine months on a barren island by eating the flesh of a winsome and gregarious little sea mammal that lived in the shallows and was clumsy as a seal ashore. When the men finally made their escape, they crammed their boat to the gunwales with its heavy pelts.

The sea otter is something of an arriviste among marine mammals. The only ocean-dwelling member of the mustelids—think saltwater weasel—it lacks blubber, the layer of specialized fat that insulates other marine mammals against the the heat-sucking properties of water. It makes do instead with its fur, the densest of any on earth. Sea otter fur packs an astounding 645,000 hairs to the square inch. Too heavy for women’s wear, the fur was fashioned into hats and trim for men’s robes. There was already a brisk Asian coastal trade in Bering’s day. But the western Pacific held few sea otters. Bering’s tattered crew brought news that a gold mine of sea otters lay just 200 miles offshore to the east. The fur rush was on.

By the time 1743 was out, legions of promyshlenniki—Siberian sable hunters—were crossing the Bering Sea in barely seaworthy boats. They soon enslaved Aleut hunters, with their nimble, skin-covered baidarka canoes, to do their sea otter hunting for them. During the next 90 years, promyshlenniki progressed slowly east across the arc of the Aleutian Islands and down the North American main, from one rocky, kelp-strewn inlet to the next, laying waste to otter and Aleut as they went.

British and American exploiters weren’t far behind. In 1778 Captain Cook touched in at Vancouver Island (not yet so named), where his sailors did a little trading. When they put in at Macao months later, they were astonished to discover that Chinese buyers would pay handsomely for the bedraggled sea otter furs they’d been sleeping on. Within a decade Americans and Englishmen were trading for sea otter furs on the Northwest Coast; trading the furs for tea, silk, and spices in China; and selling those luxury goods in the West Indies, England, and New England. The influx of new wealth from this triangular trade transformed New England’s fishing, whaling, and farming economy in the early 1800s. New England textile mills were built on sea otters’ silky backs.

The commercial sea otter trade went bust by the mid-1800s. But a velvety sea otter pelt still brought big bucks. Here on Washington beaches, sharpshooters built 60-foot derricks from which they plinked at otters far out in the kelp, letting the incoming tide float the buoyant little bodies ashore.

Finally, in 1911, an international treaty banned trade in sea otter fur. The gesture was largely moot. The animal that Bering’s naturalist, Georg Wilhelm Steller, believed “surpass all other amphibia in play and frolicsomeness” were already presumed all but extinct from Prince William Sound to Mexico.

In fact a dozen or so secretive pods hid in the wildest, most inaccessible inlets of the Aleutians and Alaska. In 1938, to the delight of Californians, locals near Bixby Creek, at Big Sur, spotted a raft of sea otters near Monterey Bay. Oregon, Washington, and British Columbia received no such happy tidings.

The Olympic Peninsula did get one lucky break that year, though, when President Franklin Roosevelt signed the act establishing Olympic National Park. And this glorious north coast where I stand got another when it escaped the mid-century mania for building scenic highways, thanks to the boot leather of William O. Douglas, Polly Dyer, and others, who hiked the long beaches in protest. Getting sea otters back would take a more dramatic intervention: a thermonuclear bomb.


Sea otters mature at three or four, then give birth to a single pup every year. They’re homebodies, too, shore huggers, averse to crossing long stretches of blue water. As a result, they expand their range extremely slowly. By the late 1950s sea otters at some Aleutian Islands had recovered in number and began to beggar their food supply. Winters brought die-offs. Given time, pioneer otters would have struck out for new habitat on their own. Instead, management-minded biologists thought to jump-start the process.

The main hitch in relocating the sea otters was the animal’s perennial challenge: its coat. Fur is a high-maintenance alternative to blubber. Sea otters’ skin hangs loosely on their bodies, and the rubbery little contortionists can pull the remotest reaches of it up to their mouth and forepaws. They’re constantly squeezing out water, scrubbing, fluffing, aligning, blowing air into the hairs, spiraling to sluice away food scraps. The air trapped in the otter’s fur provides buoyancy—it’s why they float so high—and cushions their skin from the bone-chilling water.

A caged sea otter can’t wash itself. Dump a soiled otter back into the water and it displays a disheartening tendency to become hypothermic and drown. The biologists gave up trying to transplant them.

But now a strange new bedfellow turned up in the sea otters’ Aleutian stronghold: the Atomic Energy Commission. Citing a national security provision in the law, the AEC adopted Amchitka, biggest of the Aleutian Islands, as a nuclear proving ground. In 1965 and 1969 the agency exploded underground nuclear bombs there. In 1971 it would detonate the biggest underground thermonuclear bomb in American history, 385 times as powerful as the one that destroyed Hiroshima, in a borehole a mile below Amchitka.

Biologists on Amchitka weren’t happy about the doings of the “Firecracker Boys,” as Inupiat Eskimos had memorably dubbed the atomic energy boosters. Nevertheless, they noted with interest the C130 cargo planes on Amchitka disgorging supplies and returning empty.

“How about we fly some otters out on those planes?” they asked. The Firecrackers Boys, mindful of the good publicity, agreed. In July 1969 AEC-chartered cargo planes flew 29 sea otters to Point Grenville, Washington.

It was a circus, says Karl Schneider, a biologist at the Alaska Department of Fish and Game, now retired. “Cages of frantic, filthy sea otters were opened right on the beach, surrounded by reporters and rubberneckers.” Some animals had to be prodded into the water with poles. Within two weeks 16 had washed up dead. It’s thought none survived.

Undaunted—and figuring the otters in the Aleutians were destined to get blown up anyway—the following summer biologists tried again. This time photographers were contained on a Coast Guard boat and otters were given time to acclimatize in a mesh holding pen in moving water, with a shelf where they could haul out, rest, and condition their life-giving coats. On July 21, 1970, 30 sea otters were released into Olympic National Park near La Push, where basalt reefs stripe the bottom of the protected nearshore waters.

The following year, on Amchitka, the Firecracker Boys detonated their biggest and last bomb. An estimated 1,000 to 1,500 sea otters were killed, some crushed by rockfall on shore, others dying in the water. Shock waves blew their eyeballs into their brains, Schneider says; the air in their lungs blasted through their bodies like buckshot. Waterfowl and shorebirds died, too, of course. When the bomb went off, the legs of standing harlequin ducks shot straight up through their bodies like twin spears.


When I was a kid I used to like to build bombs and blow things up,” Schneider recalls ruefully, “and those AEC guys seemed to us basically just like bigger kids with bigger bombs.” Nevertheless, he believes that more than one good thing came of it. The AEC funded not only the extraordinary otter diaspora, “it also brought all these smart graduate students together up here and fostered a lot of valuable collaboration.” One of those was Jim Estes, a lanky 25-year-old from San Diego who had just flunked his Army draft medical. Though he had studied elephants for his master’s degree, any port in a storm, he figured—even one in the Bering Sea—would do. His fieldwork on sea otters would ultimately revolutionize how ecologists understand the world. The sea otter is a god, Estes discovered—the god of the kelp forest.

Kelp are brown seaweeds. One of the biggest in the world is bull kelp, Nereocystis luetkeana, the dominant species in Washington and parts north. It consists of a rock-gripping, octopus-shaped anchor called a holdfast; a rubbery, brown bullwhip stem called a stipe; a three-quart float, which buoys the stipe; and long, translucent, amber, strap-like blades, which protrude from the float in tight clusters and form a slithery mat at water’s surface.

Kelp creates lush marine forests along rocky seashores. Sea otters raft up atop them, wrapping a frond around their abdomen as a sea anchor. In, around, and below the forest live finfish, shellfish, sea squirts, sea lions, sea eagles, gulls, and myriad other sea creatures. A discontinuous golden-brown drizzle of kelp rains food on the seafloor. Most of the kelp food web consumes this detritus, or eats other animals, and not the growing kelp itself.

Sea otters eat shellfish, and a lot of it. One 50-pound sea otter can demolish 4,500 pounds of shellfish a year. (That explains why assembled fishermen cheered when they were told that Exxon Valdez oil was killing hundreds of sea otters in Alaska’s Prince William Sound.)

When Jim Estes arrived in the Aleutians in 1970 he found himself presented with what he calls “a ready-made experiment just like a checkerboard—islands with sea otters and islands without sea otters.” He soon noticed a pattern: Islands with sea otters had kelp forests. Islands without sea otters had only pebbly green carpets of sea urchins.

Sea otters have a passion for sea urchins. Where sea otters are present, sea urchins cower in crevices eating decomposing kelp. But pluck the otters from the picture and sea urchins multiply, become emboldened, then surge en masse across the kelp forest, devouring stipes and blades, reducing the bronze jungle to a bare seafloor ecologists call an urchin barren. And that’s just the most visible effect.

Working principally in the Aleutians, Estes and a scientist named John Palmisano began to document a fascinating cascade of interactions: Barnacles and mussels grow three to four times faster in otter-inhabited kelp forests than in otter-free urchin barrens. Fish called rock greenling are 10 times more abundant if otter and kelp are present. Glaucous-winged gulls switch from a diet of 90 percent fish in otter-dominated kelp forests to about 90 percent invertebrates in urchin barrens. Bald eagles shift their diet from a roughly even mix of fish, marine mammals, and seabirds in a kelp forest to one of 70 percent seabirds, absent the otters.

Now Estes and colleagues have found that the god of the kelp forest even affects carbon sequestration. “Sea Otters Are Biocarbon Ninjas!” a recent headline proclaimed.

Researchers around the world have found that the sea otters’ story has parallels in jungles ruled by other kings. In the tropics, the loss of jaguars, cougars, and harpy eagles prompts an eruption of herbivores, which subsequently denude the habitat of understory plants. On coral reefs, fishing for sharks and other predators leads to changes in resident fish species that favor the growth of algae and limit corals. Every kind of ecosystem displays such effects. “We used to think apex carnivores were sort of icing on the cake,” Estes says. “That you could kill them off and secondary predators would take their place. That the system would keep working.” What ecologists now see is that when you take the apex carnivores out of the landscape, the landscape itself changes—“and typically becomes more impoverished,” says Estes. “Less productive, less diverse.”


The new understanding makes restoration of the otters along this Olympic coast even more important. How have they fared? That’s a question with an answer, thanks to the tenacity of a USGS biologist named Ron Jameson (now retired, though not so you’d notice) and a Washington Department of Fish and Wildlife marine mammalogist named Steve Jeffries. Jameson and Jeffries have been coming out to the coast almost every summer for 30 years to monitor sea otters.

They have witnessed a slow and steady increase in the sea otter population. The original peace dividend of 59 otters has multiplied to 1,200. Jameson hopes individuals will bust south to colonize the Oregon coast. But to do so the animals will have to navigate the minefield that is southern Washington’s Dungeness crab fishery, 10,000 crab pots strong, every pot a lethal temptation for the juvenile otters likely to form the vanguard. And then long stretches of sandy coastline, providing little shelter for sea otters, presents another obstacle in reaching the rich habitat to the south. To the north lies the Strait of Juan de Fuca, 20 miles of open water and a major shipping channel. The otters are hedged in.

Elsewhere in its range this smallest of marine mammals figures in headlines with lamentable frequency. California’s sea otters are caught in an endless wrangle with abalone fishery politics, chomped with growing frequency by great white sharks, and infected with parasites from cat feces in runoff. In southeast Alaska and British Columbia, shellfish fishermen clamor for sea otters’ blood. Lately Aleutian sea otters have suddenly all but up and disappeared. Down the gullets of killer whales, one theory has it, but no one knows for sure.

The sword that hangs over Washington’s otters is oil spills. If a ship were to strike Tatoosh Island, off Cape Flattery, Jameson says, prevailing currents could oil this whole coast. When that subject comes up among the biologists, conversation tends to taper off. What is there to say? Shipping traffic is intensifying as climate change opens the Northwest Passage. This coast already has all the protections that are available to it. Sound leadership has preserved it. Activists have battled to protect it.

Standing atop my drift log at Cape Alava, there’s not a boat as far as the eye can see. Only a passing gray whale lofting misty breaths and a pair of angular little Dall’s porpoises snipping across the waves. The otters are beginning to scull north in a lazy line. A century ago human avarice extinguished sea otters here. A fluke of international politics and public relations brought them back. That they’ve been able to thrive here is thanks to a nobler side of human nature: When sea otters were returned to these frigid waters they found that the stewards of their habitat had been able to keep this long stretch of coast essentially intact. Perhaps we will take a lesson from that.

This story originally ran in the January-February issue as “The Urchin Keepers.”