On the southeast coast of Australia, the town of Eden nestles along the shores of Twofold Bay. It was once a center of Australia’s thriving whaling industry, in part because it lies along the migration path of baleen whales swimming northward from the Antarctic. But residents say Eden’s whalers got some unusual help — from orcas, or killer whales, that patrolled offshore.

Locals such as Elsie Severs and Alice Otten who witnessed the hunts say the orcas took the lead in the hunt, herding larger migrating whales into the bay. Once the whales were confined in the bay, the orcas would then attack their quarry to the point of exhaustion. Human whalers moved in for the final kill — then shared the spoils with the orcas.

Discover this extraordinary story of interspecies cooperation on NATURE’s Killers in Eden.

To order a copy of Killers in Eden, please visit the NATURE Shop.

Online content for Killers in Eden was originally posted November 2005.

Wild dolphins face numerous threats, from hungry sharks to the entangling nets of fishing boats. But scientists have only recently begun to fully recognize another threat: chemical pollution.

Around the globe, researchers have found potentially unhealthy quantities of industrial chemicals in dolphins’ tissue and in mother dolphins’ milk. As NATURE’s The Dolphin Defender shows, one group of contaminants is of special concern: polychlorinated biphenyls, or PCBs.

More than 200 kinds of PCBs have been used as flame retardants and electrical insulators in products ranging from cereal boxes to plastics. Although they were banned in the United States and many other nations in the late 1970s, PCBs continue to leak into the oceans from river sediments and other sources. The chemicals enter into the food chain and ultimately into fish, which dolphins eat. Researchers with the National Institute of Standards and Technology in Charleston, South Carolina, say that dolphin blubber carries some of the highest PCB concentrations found in any wild animal.

Although it is difficult to link PCBs to specific health problems, dolphin researchers have found some troubling trends. One is that female dolphins with high levels of PCBs appear to have lower pregnancy rates than less-contaminated females. That may be because PCBs interfere with the reproductive process.

Another finding of concern is that heavily contaminated female dolphins that do get pregnant often lose their first calves. That may be because the mother dolphin “burns” blubber to make milk. The PCBs and other compounds stored in the blubber become part of the milk and are transferred to the calf. The chemicals may harm the baby dolphin’s immune system, making it less able to fight off infections from viruses and bacteria.

Scientists have also found that PCB-contaminated male dolphins don’t develop sexually. Even more alarming, research shows PCB similarly affects other members of the dolphin family, such as orcas. As The Dolphin Defender shows, the orca population in Puget Sound, off Seattle, Washington has dwindled in the past 20 years. The high mortality rate and undeveloped reproduction systems were attributed to the high PCB levels in the orcas’ tissues.

Researchers are still trying to verify such links. They are now conducting several long-term studies of dolphin populations around the world. PCBs aren’t the only target; pesticides and other industrial chemicals that wash into the ocean are also being measured and analyzed. Eventually, conservationists hope the studies will lead to a better understanding of this invisible threat to dolphin survival, which will then lead to possible solutions.

Two decades ago, ecologist Andrew Trites of the University of British Columbia in Vancouver started wondering why populations of northern fur seals, a once economically important marine mammal that lives in the North Pacific, were declining. That work eventually got him involved in trying to solve another major ecological mystery: Why have some populations of Steller’s sea lions declined so dramatically off the coast of Alaska over the last few decades?

Some researchers blame giant trawlers, which scoop up tons of fish, and have supported government moves to ban or limit catches in order to keep food supplies available to sea lions. Others believe that uncontrolled whaling decades ago sparked an ecological domino effect that is just now affecting the sea lions. Still others, including Trites, say many factors may be to blame including climate change, predation by killer whales, and a natural ecosystem shift that altered the nutritional quality of prey consumed by sea lions.

NATURE recently spoke with Trites, whose work is featured in NATURE’s A Mystery in Alaska, about the complexities of Alaska’s offshore ecosystems. For instance, he notes that while sea lion populations in Southeastern Alaska tend be stable or increasing, populations elsewhere have shrunk with few signs of recovery. “You can’t assume the factors that are influencing one region are the same somewhere else,” he says.

Where did you start in your own thinking about this problem?

I originally thought, as did most people, that there was probably a pretty simple cause-and-effect relationship between fisheries and sea lions. An open-and-shut case: There was a shortage of pollock because of fishing, and sea lions could not find enough to eat. But when I looked at the numbers, I couldn’t find a relationship between fish catches and sea lion populations. That led me to dig deeper.

I and other researchers started comparing different populations of sea lions (some of which are declining, some of which are stable and increasing). We wanted to know what’s different about what they eat and how long it takes them to find food. We’ve also looked at the possible effects of climate change and predation. Eventually, we concluded that no single factor can explain why the numbers have gone down, but there are some underlying factors that tie things together. For instance, the composition of the fish community has changed since the 1960s and ’70s, and is now dominated by pollock and flatfish. These species were there 25 to 50 years ago, but were not as dominant. There were more crabs and fish such as herring and sandlance. So there has been a major shift in the types of fish now available to sea lions.

Ecologist Andrew Trites believes many factors are at play in the sea lion mystery.

And you’ve found that some fish are better food for sea lions than others, right?

When we’ve done feeding experiments with trained sea lions, we’ve found that while pollock is now a major part of the sea lion’s diet, it may not be the healthiest thing for them to eat. The fattier fish such as herring that they used to eat more of, had a lot more calories than pollock. So a sea lion has to eat a lot more pollock to get enough energy to do well.

Now, an adult probably can do perfectly well on a pollock diet. But we suspect a young sea lion that needs more energy to grow doesn’t have the stomach capacity to hold all the pollock it needs to meet its daily requirements. So, while sea lions may not be starving to death, some appear to be nutritionally compromised. And that could make them more susceptible to disease, stunt their growth, or make them more vulnerable to killer whales.

Poor nutrition works in very subtle ways. It removes one animal here and there, but you don’t see massive die-offs. That’s what’s been so perplexing about getting a quick answer to why sea lions have declined.

So does that mean areas closed to pollock fishing should be reopened?

Right now, fishing is closed around the [sea lion] rookeries because there was a fear that fishing was behind the sea lion decline. But there was never any data and still isn’t any evidence that links the two. We therefore need to go the next step and re-open fishing in a few areas, but not in others, and then compare what happens. We need to think about this as a carefully controlled experiment and an opportunity to learn once and for all whether fishing has an effect on Steller’s sea lions. Just because sea lions and fisheries target the same species, doesn’t necessarily mean that they compete with each other. It is like two people who breathe the same air in a room. They do not compete with each other unless the room is sealed and their supply of oxygen is limited.

What about the role of killer whales?

From the ecological modeling we’ve done, it appears unlikely that killer whales caused the decline. But sea lion numbers are so low now that predation by killer whales could be preventing them from recovering. The sea lions may be caught in a “predator-pit.”

What have you learned from trying to tackle this mystery?

That things are not always what they first appear to be. That it takes very careful sleuthing to follow a line of evidence and not jump to conclusions without having the facts to support them. Many people jumped to the conclusion that people must be behind the sea lion decline. But research is showing that a suite of changes occurred in the North Pacific over the past 50 years including a shift in ocean climate, a flip in the dominance of key species in the ecosystem, and a corresponding change in sea lion diets and the nutritional value of their prey.

Also, you have to think about your value system when passing judgment over ecological changes. There is a lot of rhetoric about how unhealthy the Bering Sea is because some species that people value have declined. But it appears that the Bering Sea and Gulf of Alaska can exist in more than one state, and that you probably can’t have all of the species there all of the time in high numbers. If your favorite species in the world were pollock or flatfish, you’d be ecstatic right now. Our perceptions of ecosystem health tend to be based on which species we most value, which are a very small subset of the whole ecosystem.

Spanish sailors called them the “whale killers.” The Haida of British Columbia knew them as the “killing demons.” To the Japanese, they were “fish tigers.”

Whatever the name, seafarers have long been awed by the hunting prowess of the large black-and-white dolphins known as orcas, or killer whales. Among their admirers are the whalers who sailed Australia’s Twofold Bay from nearly a century ago up to the 1970s. As NATURE’s Killers in Eden shows, these human whale hunters say they formed a partnership with the orcas, which helped them herd and hunt whales.

Those stories are difficult to substantiate. But researchers say it is certainly true that orcas exhibit remarkably creative, complex, and often cooperative hunting strategies. The highly social animals, which typically travel in groups called “pods,” are known to feed on everything from fish and seabirds to seals and giant blue whales.

Orca pods living in particular waters tend to specialize in certain species. In the North Atlantic, for instance, some orcas follow schools of herring. Working together, they’ll surround a school and herd it into a tight ball — sometimes by releasing a curtain of bubbles. Then they’ll take turns slashing through the school, stunning or killing fish with a slap of their powerful tails. Finally, they eat the dazed or deceased fish one by one.

Other pods specialize in picking off seals or sea lions. Along the California coast, for instance, they’ve been seen tossing unfortunate seals high into the air, probably in an attempt to stun them. Along the coast of Argentina, mother orcas teach their young an equally impressive hunting tactic — the killer whales literally fling themselves up on beaches in pursuit of young seals, then flop back into the sea with their meal. Apparently the taste of seal is worth the risk of getting stranded.

Orcas exhibit remarkably creative, complex, and often cooperative hunting strategies.

Orcas exhibit remarkably creative, complex, and often cooperative hunting strategies. Some orcas even use bait. They’ve learned that they can lure in a flock of seagulls by regurgitating fish and letting the scraps float to the surface. When the gulls land to eat the fish, they become the orcas’ feast instead.

In polar seas, orcas have discovered another trick. When penguins or seals take refuge on a piece of floating sea ice, killer whales rock the fragile raft, trying to knock off its occupants. Or, better yet, they use their bodies and tails to stir up waves that wash their prey off the ice and into the water, where another orca waits to snap them up.

Perhaps the most spectacular — but least understood — orca feeding behavior involves great whales. The orcas, which can reach 28 feet in length, sometimes take on whales many times their size. Usually, however, they go after young whales. First they’ll try to separate the youngster from its mother by chasing it for hours or days. Then they’ll surround the young whale and try to block it from reaching the surface to breathe.

Despite their fierce reputation, orcas have little taste for one seagoing animal: humans. Researchers say there are no documented cases of a wild orca intentionally hunting a human, although there have been attacks in sea parks. And there have been several cases where an orca may have mistaken a surfer or swimmer for some other animal.

The whalers of Eden, however, say orcas were not a threat. Instead, they acted as partners, steering their boats to whales out in the bay and, helping sailors who had fallen overboard back to safety. Far from killers, the whalers of Eden say their orcas were saviors.

When Danielle Clode was a teenager, she came face to face with a killer. A killer whale, that is. Actually — the skeleton of a killer whale.

In the early 1980s, Clode — who is featured in NATURE’s Killers in Eden — was sailing along the coast of Australia with her parents. The family had entered Twofold Bay on the continent’s southeastern coast. There, in the old whaling port of Eden, Clode visited a museum that included the skeleton of an orca, or killer whale, that had become a local legend.

The orca’s name was Tom, and an elderly guide told Clode that Tom had once led a pod of killer whales that helped the town’s human whalers catch and kill their quarry. Indeed, the guide even pointed out wear marks in Tom’s jaws where, he claimed, the orca used to carry ropes while helping the humans.

“The guide was fantastic, and the story absolutely intrigued me,” Clode recalled recently. “I ended up doing a school project all about it.”

Years later, after earning an advanced degree in biology and becoming a science writer, Clode remembered the killers of Eden when she was looking for a book topic. Soon, she was scouring the scientific literature, trying to see if it could really be true that wild orcas — among the sea’s fiercest predators — would actually cooperate with human whalers. “There was a lot of skepticism about the stories,” she says.

Clode learned that since she had written her report as a teenager, scientists had made further discoveries about orca hunting behavior. They found that these whales have remarkably sophisticated hunting strategies, often cooperating to corner and then eat everything from schools of fish to large whales.

“They have a very good ability to take advantage of new situations,” Clode says. And that, she believes, is more or less what happened in Eden. Killer whales probably herded humpbacks and other large whales into the shallow waters, where they would then separate young or sick whales and kill them. Clode says the orcas would typically eat only the tongues, leaving most of the rest of the body behind.

In the 1980s, Clode visited a museum that included the skeleton of an orca, named Tom, that had become a local legend.

The orcas’ attacks were not without risk. “It’s a fairly dangerous activity — a big angry whale can damage a killer whale’s fins and body . . . they can end up pretty hurt.” So once the orcas learned that human whalers might spare them some of that risk it seems plausible that they learned to help out. “It may have been a kind of mutual exploitation arrangement,” she says. “Certainly the basic hunting strategies that are in the stories are similar to what’s been seen elsewhere.”

Those stories are remarkable, she says. For instance, locals such as Doug Ireland and Alice Otten state that when large whales arrived in nearby waters, the orcas would signal their human allies by “lobtailing,” or slapping their large flukes, or tails, against the surface of the water. The orcas would even lead the whalers out at night, showing the way to prey by slapping the water in the inky blackness. Elsie Severs, another eyewitness, recounts how on one occasion, her father, a whaler, fell in the water and Tom protected him from sharks. Other whalers who were drowning claimed to have been dragged back to the surface by the killer whales.

It may never be possible to authenticate such stories, the earliest of which was recorded in 1844. By the 1930s, whalers had destroyed many whale populations in the Southern Ocean, and the Australian whaling industry slowly ground to a halt. Legend has it that when a local resident killed a beached orca — in essence breaking the pact with the orcas — the killer whales also left the waters around Eden. Clode, however, doesn’t believe that’s the reason the orcas left. “It’s tempting to conclude that the killer whales started leaving after the death of Jackson [the beached orca]. And there was a loss of that trust that had built up between humans and killer whales. But it’s hard to exclude the fact that the food supply was declining; the number of whales being caught was declining dramatically.”

Clode says that modern science may explain some of those stories. For instance, it’s clear that orcas do use lobtailing as a form of communication. And researchers have found that when one member of a killer whale pod dies, the others may scatter and act erratically — perhaps also contributing to their disappearance from Eden.

But Clode is happy to report that orcas and other whales have since returned to the area. Indeed, Eden has become a draw for people who want to watch whales … not kill them.

The rich, shallow waters of Australia’s Twofold Bay — featured in NATURE’s Killers in Eden — are a whale’s dream. The bay, which lies along the migration path of baleen whales such as humpbacks, has plenty of food and protection from heavy coastal currents.

But a century ago, Twofold Bay was also a whale’s nightmare — the site of cooperative hunting between killer whales, or orcas, and human whalers. Orcas would station themselves in strategic places, waiting to herd young or sick baleen whales. Human whalers would then set out in small open boats from shore, armed with sharp harpoons and strong ropes.

According to historians, the earliest record of a whale being killed in Twofold Bay dates to 1791. Just a few decades later, in the 1820s, came the first formal whaling stations. Then, in the 1830s, whalers erected the first buildings at the port of Eden. Later, that station became the property of Alexander Davidson and his family. Their stories of the remarkable cooperative hunting behavior of Eden’s killer whales — and particularly a pod led by a killer whale named Old Tom — have captivated visitors, historians, and biologists ever since.

As early as 1903, a reporter from The Sydney Mail was writing about the unusual partnership. “When a whale is passing north it is driven into Twofold Bay by whales known as the killers,” he noted. “When the killers succeed in driving the whale into the bay they leave off the attack and wait for the whale boats to come. Any attempt the whale makes to go out to sea the killers resent with all energy by snapping pieces out of it … all the time the killers are at work.”

The growth of whaling in Eden was part of a national trend. In fact, commercial whaling was one of the country’s earliest and most lucrative industries. By the mid-1800s, Australia’s fleet was second only to America’s, capturing thousands of southern right, humpback, and blue whales a year. The whales provided everything from oil for lamps to bone stiffeners for corsets.

By 1900, however, the industry was in decline, as some whale populations began to dwindle toward extinction. By 1930, whaling had ended in Eden — an end punctuated by the death of the killer whale named Old Tom. Following a brief resurgence after World War II, whaling in Australia ceased for good in 1978. Today, the Australian government opposes the killing of whales for profit.

More whales are now returning to Australia’s coast, some to Twofold Bay, where whale watching is now an attraction. It seems that with the end of whaling, the bay has again become a kind of Eden for migrating whales.

PC users: Right click on the wallpaper and select “Set as Wallpaper.”

Mac users: Save the image to your desktop, then select it via the Desktop tab of your Appearance control panel.

Killers of Eden
http://www.killersofeden.com/index.htm
A detailed site devoted to the orcas and history of Twofold Bay.

Orca Fact Sheet
http://www.acsonline.org/factpack/KillerWhale.htm
Learn more about killer whales — from their mating behavior to their current population status.

Eden, New South Wales
http://www.marinews.com/fishing_details.php?recordid=388
Journalist Rod Clarke offers a comprehensive report on the bustling fishing town.

Eden Whale Festival
http://www.edenwhalefestival.com/
Celebrate the annual whale migration through Twofold Bay.

Killer Whale Museum — Eden
http://www.killerwhalemuseum.com.au/
Visit the museum that is home to Old Tom’s skeleton.

Killer Whales Hunt for Herring
http://jeb.biologists.org/cgi/content/full/208/12/2459/DC1
Watch videos of killer whales prey on herring.

Gull-trapping Killer Whales Show Learning Skills
http://www.abc.net.au/news/newsitems/200508/s1445574.htm
Killer whales are one of three known animal species to possess “cultural learning.”

Predation Behavior of Transient Killer Whales in California
http://www.montereybaywhalewatch.com/Features/KillerWhalePredation0210.htm
Find out more about the hunting techniques of killer whales in Monterey Bay.

BOOKS

Baird, Robin W. KILLER WHALES OF THE WORLD, NATURAL HISTORY AND CONSERVATION. Stillwater, MN: Voyageur Press, 2002.

Clode, Danielle. KILLERS IN EDEN. Sydney: Allen and Unwin, 2002.

Hoyt, Eric. ORCA: THE WHALE CALLED KILLER. New York: Camden House, 1990.

Mead, Tom. KILLERS OF EDEN. New York: Vantage Press, 1994.

Suzuki, David. ORCA: VISIONS OF THE KILLER WHALE. San Francisco: Greystone Books, 2004.

Produced and Written by
KLAUS TOFT

Principal Photography by
KLAUS TOFT
RORY MCGUINNESS ACS
DAVID PARER ACS

Music
RICKY EDWARDS

Editing
PAUL CANTWELL
KEN SALLOWS
KLAUS TOFT

Computer Visual Effects
GREG McKEE
ALISTER FERGUSON
DEAN ERVIK
MARK KENNEDY
MARK ROBINSON
DAN MAVRIC
NICK HILLIGOSS
JEREMY FISHER

Location Creature Effects
GREG McKEE
TIM SHEPPARD
MEL MILAMOVIC
NICK HILLIGOSS

Camera Assistant|
CAMERON DAVIES

Dive Coordinators
CHE McGUINNESS
MILES PETTY

Location Sound
KLAUS TOFT
CAMERON DAVIES
ELIZABETH PARER-COOK
ROGER PAYNE

Additional Photography
NANCY BLACK
PETER THOMPSON
GIL ARBEL
PIERRE RAKUS
MALCOLM LUDGATE
RICHARD TODD
NATURAL HISTORY
NEW ZEALAND LIMITED

“Siege Of The South”

Footage Provided By
SCREENSOUND AUSTRALIA

Additional Music
GEORGE ROYTER
BOB ROBERTS
KIM BASTON

Production Coordinators
AMANDA WRAY
ESTHER RODEWALD

Production Assistants
CAMERON DAVIES
ROBERT HAYWARD

Set Design
RUDY JOOSTEN

Studio Assistant
EDDIE STRONG

Archives
CLARE CREMIN
JENNY GIBSON
ANNETTE COOPER

Sound Mixing
MARK STREET

Sound Editing
MARK STREET
LYNNE BUTLER
IAN BATTERSBY

Colourist
JUDE FINLAYSON

On-line Editors
RONNIE OLIVER
ALAN RYAN
DAVID HUTCHINSON

Production Manager
SACHA GREGSON

With Special Thanks to:
GREG McKEE
DANIELLE CLODE
ALICE OTTEN
ELSIE SEVERS
DOUGLAS IRELAND
BILL BLAXTER
MARGARET BROOKS
JOHN POHL

Yuin Dancer
WARREN FOSTER

Thanks Also to:
Robert Hayward
Lee Cruse
Osley Harrison
Frank Davey
Christian Cole
Stuart Manson
Jim McGrath
Leon Laragy
Amanda Wray
Peter Severs
Jared & Izak Graham-Higgs
Joe Walker
Sam Foley
Andy Edwards
Rafiq Copeland
Peter Koval
Madeleine Toft
Natalie Toft
Pambula Surf Lifesaving Club
Tom & Florrie Bobbin
Rene & Fay Davidson
Sgt. James Hinkley, Eden Water Police
Ossie Cruse
Eileen & Daniel Morgan
Mary Mitchell
Tom Mead
John Bradshaw
Trevor Close
Bob Daly
Fritz and Jenny Drenkhahn
Wendy Noble
Marjorie Ireland
Jim McCormack
Michael Lucas
Kevin & Garry Warren
Simon Watt
Bruce Permezel
Soren Toft
NSW National Parks & Wildlife Service
National Library of Australia
Eden Killer Whale Museum
Edrom Lodge
State Library of NSW, Sydney
National Gallery of Australia
Museum Victoria
State Library of Victoria

Executive Producer for Granada International
MARK REYNOLDS

Executive Producer
DIONE GILMOUR

A Production of ABC Australia in association with Granada International

© 2004 Australian Broadcasting Corporation

For NATURE

Series Editor
JANET HESS

Supervising Producer
JANICE YOUNG

Producers
JILL CLARKE
PATTY JACOBSON

Associate Producers
IRENE TEJARATCHI
GIANNA SAVOIE

Production Secretary
RACHAEL TEEL

Manager
EILEEN FRAHER

Production Manager
JULIE SCHAPIRO THORMAN

On-line Editor
BRUNO PELLEGRINI

Narrated by
PAUL CHRISTIE

Sound Mixer
BRIAN BEATRICE

Series Producer
BILL MURPHY

Executive in Charge
WILLIAM GRANT

Executive Producer
FRED KAUFMAN

This program was produced by ABC Australia, which is solely responsible for its content.

© 2005 Educational Broadcasting Corporation

All Rights Reserved

Web Credits

Director of Production
DANIEL B. GREENBERG

Producer
TANNER VEA

Production Assistant
DANIEL ROSS

Writer
DAVID MALAKOFF

Designer
MICHAEL DIMAURO

Creative Director
NICK MILLER

Pagebuilding
BRIAN SANTALONE

Technical Director
BRIAN LEE

Photos for “Overview,” “Expert Hunters,” “Face to Face With a Killer,” and “Resources” © D Parer & E Parer-Cook / AUSCAPE. Photo for “Australia’s Whaling Industry” © Rene Davidson. Other photos from “Killers in Eden.”

Thirteen Online is a production of Thirteen/WNET New York’s Kravis Multimedia Education Center in New York City. Dan Goldman, Executive Director, thirteen.org. Bob Adleman, Business Manager.