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"Shark Attack!"

PBS Airdate: August 5, 1997
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ANNOUNCER: Tonight on NOVA—

ROD ORR: All I could see really was the teeth out of my left eye.

ANNOUNCER: Frightening.

KIRK JOHNSON: It folded me in half so quickly I didn't have any idea what was going on—

ANNOUNCER: Formidable.

KIRK JOHNSON: And the water was turning all dark around me with blood.

ANNOUNCER: Unforgiving.

KIRK JOHNSON: Holy smokes!

ANNOUNCER: But are sharks really man hunters? Science takes a hard look at one of our greatest fears. Shark Attack.

NOVA is funded by Prudential.

Prudential. Insurance, health care, real estate and financial services. For more than a century, bringing strength and stability to America's families.

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Merck. Pharmaceutical research, dedicated to preventing disease and improving health. Merck. Committed to bringing out the best in medicine.

The Corporation for Public Broadcasting and viewers like you.

JOE MORTON: The clear blue waters and rolling surf of the California coast are a playground in the sun. They're also the hunting ground of one of the world's most dangerous creatures: the great white shark. Encounters between sharks and surfers are rare, but unforgettable. They strike with no warning and little chance of escape.

KIRK JOHNSON: When it first hit me, it was such a hard blow. I mean it really hit hard.

JOE MORTON: Held in the jaws of a fifteen foot shark, Kirk Johnson thought it was the end. He felt his body shaken violently. But as quickly as it began, the attack was over.

KIRK JOHNSON: And the shark then just let go of me. And I came to the surface. And the water was turning all dark around me with blood.

JOE MORTON: His back torn open, Johnson was barely able to get to shore. Why did the shark attack, and then suddenly release him? Surfer John Ferrara has asked the same question. While paddling his board, Ferrara was hit by an immense force.

JOHN FERRARA: I describe it as about the size of a Volkswagen, the body of it, just the girth. And the fin of it was about three feet out of the water while it was just going past me very slowly. And you pretty much know exactly what it is, it's something wanting to eat you, you know? And you want to get the hell out of there.

JOE MORTON: But if the shark had wanted to eat John Ferrara, why didn't it? Like most surfers who are attacked, both men escaped, and returned to the water as soon as they could. Some believe surfers are tempting fate, but is the great white shark really a man hunter? The elusiveness of these sharks has shrouded them in mystery. Yet new research sheds light on why attacks happen. As science replaces sensationalism, these sharks may lose their reputation as monsters of the deep. To understand sharks, researchers must delve into their domain. The Farallon Islands lie just twenty miles off the coast of California, west of San Francisco. In Native American legend, their sinister, jagged peaks were said to be the islands of the dead. The Farallons are also a regular feeding area of the great white shark. There are few places in the world where great whites can be so closely observed in the act of killing. Their prey are usually marine mammals, like these California sea lions. Some members of this group have had narrow escapes. But they are not the only animals facing danger. In the Fall, the presence of northern elephant seals ushers in the hunting season. It's a busy time for biologists like Peter Pyle, who spends much of the year studying birds. Now he turns to pinnipeds, seals and sea lions, and the sharks that prey on them. California sea lions haul out here to rest throughout the year, safe on the shore, but often enduring plagues of flies. In the autumn, they are joined by juvenile elephant seals coming ashore for the first time in months. The seasonal concentration of young, naive seals draws white sharks like a magnet. Hauling out on this rocky ledge is a struggle, especially at high tide. Huge waves can wash the seals right back into the surf. Just a few feet off shore, the sharks are waiting for them. And Peter Pyle is waiting for the sharks.

PETER PYLE: The shark is a visual predator, the White Shark here, more than anything. It stalks in the depths, probably behind ridges, against the rocks, where the pinnipeds are going to have a harder time seeing it. And then, when the time is right, it will rush up from below and strike the pinniped at the surface.

JOE MORTON: Stealth and surprise are critical elements in a successful attack. The blood slick and agitated gulls draw the attention of the Farallon researchers waiting at a vantage point high on the island. To understand more about where and how sharks attack, the researchers need to pinpoint the location. They will later visit this site to check the water depth and clarity and whether the kill takes place over rock or a sandy bottom. But now, they want to observe the feeding while it's happening. Pyle hurries to the boat landing. There, he joins shark biologist, Scot Anderson. If it's a big seal, it may take the shark half an hour to eat it. This gives the team time to get on the water and alongside the kill. Rough seas make their job difficult; their boat is only fourteen feet long.

PETER PYLE: The first couple of times we went out in boats, we approached it very cautiously, we circled in, we kept our distance, we looked from a distance, we took pictures from a distance. And then slowly, we realized that the sharks would come up to the boat, but they didn't have any real intention on doing anything, they were more or less just checking us out.

SCOT ANDERSON: It's very exciting to see a shark in the water. These sharks are huge, you know? We're talking fifteen to eighteen feet with a weight of maybe three to four thousand pounds. And they have an amazing presence in the water. As they move through the area, they're very controlled. They know where they're going before they get there, and so you just are kind of in awe of this silent, huge predator moving through the water.

JOE MORTON: At the attack site, the two men lower underwater cameras beside the boat. Other sharks may move in to get a bite of the prey, but if the killer is a big animal, they stay away. Scars on their skin suggest great whites may at times turn on one another.

PETER PYLE: We're out there getting as much video as we can on these sharks, and a lot of them have scars of various types. Some of them look like aggressive scars where maybe one shark has come in and bitten another to kind of warn it away from the carcass. A lot of the females seem to have scars along the gills which may relate to mating scars. And these scars are pretty permanent. They look white at first, and then they turn black. And after a while, we'll mark down all the spots where these scars are, and we'll be able to use those in our individual I.D.

JOE MORTON: Scot Anderson has identified more than forty white sharks here. Many return time and again. After the initial violent attack, sharks feed in a controlled, almost calm manner, contrary to the notion of a feeding frenzy. A shark can consume a four hundred pound meal in ten immense bites of up to fifty pounds each. The Farallon researchers are accustomed to sharing these waters with feeding sharks. They witness up to seventy attacks each season. Still, working in a boat that is smaller than the sharks that surround it takes courage.

PETER PYLE: It's always a thrill when you've got white sharks circling around below you. I don't think we'll ever get over that thrill. They're looking at us, they're curious. It's interesting in that the biggest ones seem to be the smartest about it and know sooner that we're not edible and disappear quicker. It's actually the little ones that we're a little more worried about, maybe the nine to twelve footers that we see here, because they're less experienced. We don't know what they're going to do, they're less predictable, as far as I'm concerned. They're the ones that may end up getting a little excited near the boat. I think they're also the ones that might be hitting surfers more.

JOE MORTON: Surfers are more vulnerable to great white sharks than anyone else in the water. As they skim the surface of the waves, underneath them, sharks may be lurking. But their presence here may have little to do with seeking human prey. Many of the best surfing beaches are near the breeding colonies of seals and sea lions. In fifty years, there have been fewer than eighty attacks on humans in California, only seven fatal. With so many people in the water, it's surprising there haven't been more. Perhaps the attacks that do take place are cases of mistaken identity. A surfer paddling out to sea, arms waving and feet trailing, may look like a seal. But even if they look like the favorite food of great whites, surfers don't taste the same. Compared to an elephant seal, a human body must seem bony. The scars on animals here at Ano Nuevo, south of the Farallons, testify to their shark encounters. Seals and sea lions have been the prey of large sharks for some thirty-five million years. Ferocious as these male elephant seals may be, they are no match for sharks. As females look on, bulls, over three times their weight, fight for mating rights. Protection of breeding colonies, like this one, has brought seal populations back from the edge of extinction. Forty years ago, this beach was barren, now it is home to over ten thousand animals. It is literally a pup factory. But as soon as these babies are weaned, they will have to leave the beach and start to feed themselves. It will be months before they see land again. Many of those feeding contentedly at their mother's sides will find themselves in the shark-infested waters of the Farallon Islands, seeking shelter on the wave-swept rocks. It happens every Fall, and the biologists will be waiting. Scot Anderson has studied great whites for nearly ten years and has a down-to-earth view of the drama between predator and prey.

SCOT ANDERSON: The great white shark is an apex predator that feeds on marine mammals. When they're young, they feed on fish, as they grow older, they begin feeding on strictly marine mammals. And that puts them at the top of the food chain. The elephant seal is considered to be their preferred prey at the Farallons in that they're solitary animals, they're easy to capture because they're slow swimmers and they tend to be naive when they're young and they sit at the surface, which they shouldn't do.

JOE MORTON: As it patrols beneath the waves, a shark can see the silhouettes of prey above. Great whites cruise sixty to one hundred feet under water, close enough to maintain eye contact, yet far enough to ensure stealth. Sea lions are attacked far less often than elephant seals, perhaps because they travel in groups, with more pairs of eyes on the look-out for danger. These warm-blooded mammals are swift and agile, and difficult for sharks to catch. The great white's hydrodynamic design is adapted more for cruising than sustained sprints. But it is equipped for short high-speed dashes, propelled by an awesomely powerful tail. The slow-moving elephant seal doesn't stand a chance. The shark rushes up from the bottom in an ambush attack. A lethal first bite insures the seal can't fight back. The seal dies quickly from loss of blood, while the shark thrashes its head back and forth, cutting through muscle, bone and blubber. It's a bite that requires the powerful jaw of an adult great white, as biologist Ken Goldman explains.

KEN GOLDMAN: This is a jaw out of a six foot animal, definitely a juvenile white shark. And two things to really notice are the narrowness of the teeth, and nice spiky, pointy teeth, as well as at the top, the teeth are also fairly narrow, fairly strong, spiky teeth. Perfect for feeding on fish, very similar to other shark's teeth that are specifically designed to feed on fish. As they get older, and move to feeding on the seals and sea lions, the bottom teeth broaden out at the base, flatten out across here, designed more to grab a hold of the prey. And so you never want to grab a hold of anything that would be able to get out of your mouth, so the teeth are pointed back in, giving grip. The top teeth then come down and are removing that bite.

JOE MORTON: The infamous jaws of the great white shark are remarkable in other ways. Its upper jaw is not firmly joined to the skull, but can jut forward to clamp down on prey. And the shark has a seemingly endless supply of fresh, sharp teeth. When front teeth are damaged, back ones move forward to replace them. A shark may grow and discard thousands of teeth in its lifetime. Great Whites may live up to seventy years, but this, like much about the shark, is still uncertain. They have been captured, but never successfully kept in captivity. Their movement and behavior in the wild is now better understood thanks to remote tracking.

KEN GOLDMAN: Well the tracking of sharks out at the Farallons consists of feeding a shark one of these. This is a sonic transmitter, and it relays temperature and swimming depth of the animal to me. So, when a shark has attacked a seal, we'll go out in the boat and put this in the water with a small piece of seal or sea lion blubber, and when the shark ingests this, we're able to start tracking immediately. It's done within the natural predatory sequence.

JOE MORTON: Goldman finds that large individuals tend to feed in the same place each year, patrolling areas where they have been successful before. Younger, less experienced sharks, move around the islands looking for chance encounters with prey. The transmitters also show that the body temperature of great white sharks is much higher than that of the surrounding water, and, like warm-blooded mammals, the shark maintains a constant internal temperature.

KEN GOLDMAN: It's probably a very effective evolved mechanism for these animals. This is an animal that is an active hunter in very cool water conditions, and it's hunting a very swift and agile prey. So, my hypothesis is that if the animal was not regulating its body core temperature being much higher than water temperature, it would probably not be an effective hunter.

JOE MORTON: Being warm-blooded also helps the shark to digest blubber, a very rich source of energy. And no prey offers more blubber than a whale. The great whales, like these humpbacks, may have once been important to the shark's diet. Now, these whales are scarce, and to find a carcass washed up on a beach is a rare treat for a foraging shark. If there is one to be found, the shark's acute sense of smell will detect it, even from miles away. This humpback whale will provide a huge meal, hundreds of pounds of blubber. The challenge for the shark is to find the proper angle to take a bite out of the massive carcass. A meal like this can sustain a great white for over a month. But scavenging whales is not a reliable source of food. A large predator must have easy access to living prey, as the great white shark has at the Farallons. In these rough waters where seals abound, Scot Anderson has devised a way to get a whole new view of a shark attack. He attaches a video camera to a board. Research shows that this particular shape will provoke great whites. Scot and Peter Pyle motor out to a place they know is teaming with sharks and float the board in the water. Remarkably, no animal bait is needed to attract the sharks. They are drawn simply by the shape of the board, oblong and roughly six feet in length, the shape of a seal, a sea lion, or a floating surfer. Sometimes, the sharks merely investigate the board and swim by. But at other times, they stalk and attack. Following the initial strike, the sharks may hover momentarily, but they rarely return for a second bite. They know a good thing when they taste it, and this isn't it. The fierceness of this attack startles even the most unflappable scientist.

SCOT ANDERSON: Well last year I was scared by a shark that came up to investigate the board that I had out when it was really close to the boat, actually bringing it in to the boat, about a foot away, and when the shark attacked it, it went violently through the area. Incredibly quick, incredibly loud, and it really scared me. So it made me realize that there's certain times when dealing with these animals where there is some danger. But most of the time, when they're around the boat, they're very controlled, they're looking for food, and it usually is, seems pretty safe to me for the most part.

JOE MORTON: It's safe, for the most part, for other people working near the Farallons, abalone fishermen collecting highly prized shellfish. Climbing into waters inhabited by great whites may seem a questionable practice. But even here, the risk of attack is slim. Ninety percent of shark attacks take place at the surface, most others in mid-water. On the sea floor, divers are relatively safe. But diving with open wounds or holding fish and other bait is asking for trouble. The divers must keep a sharp lookout for cruising great whites, as they measure the abalone to make sure they meet legal standards. Rod Orr holds the dubious distinction of having been attacked twice in pursuit of abalone.

ROD ORR: Just at the edge of vision I saw something, but I didn't realize what it was, and then the little light dawned, and what I could see was the gills on this white shark. And the shark was like ten, eleven foot long, and it closed on me, but when I looked back at it, it had closed the distance by half, and then it started coming in fast. And I knew it was after me. But I tried to get behind this rock. And when I tried to get behind it, the shark came in on my left side, his mouth just opened up, and his jaw actually just came out of his mouth. And I had a row of teeth marks up in my scalp where he bit down. And the worst damage was probably to my nose and to my lower eye, because I had a hole through the upper eyelid and the bottom eyelid. All I could see was really, was the teeth out of my, you know, from my left eye, I could see the water down there. And I could see all the teeth on the top jaw and the bottom jaw. But I was face down in it, and it was just like, they looked huge, they looked like they were three inches long. I know they weren't that big, but they were just all white. And I could see about ten or twelve teeth. I think he realized that I wasn't a seal at that time, but why he didn't finish biting the head off me, why he didn't thrash I don't know. It's just luck of the draw.

JOE MORTON: Why did the shark release him? Most likely, a bony human didn't seem a worthwhile meal. But there are sharks in other parts of the world with less discriminating tastes. Perhaps these predators are even more to be feared. In tropical waters throughout the world, including here in Hawaii, there lives a shark responsible for more attacks on humans than even the great white. In a place of golden beaches where surfing is a way of life, more people are exposed to danger. These clear and inviting waters are also home to the tiger shark. As the largest shark on most Pacific reefs, tigers rule as apex predators, feeding on fish and lobsters, seals and turtles, rays and other sharks. They are said to eat just about anything that comes their way: floating license plates, garbage from ships, even humans. Hawaiian culture has a special word for sharks that eat people: niuhi. They are animals both feared and respected. Local surfers today reassure themselves in different ways about the dangers of shark-infested waters.

SURFER: Oh, I'm not worried about the tiger shark because I feel like that's my aumakua, which mean it's, it's a religious belief that native Hawaiians have about the sharks.

SURFER: It depends, if there's a lot of people around, I don't worry about it too much, because the odds of getting eaten is probably a little less. But when you go surfing in other secret spots and stuff, that's when you're always like looking down and checking it out.

SURFER: If you were to go surfing, go snorkeling when it's flat, you'd see a million turtles, and that's what the tiger sharks eat.

JOE MORTON: Green turtles are common in the tiger shark's diet. Whole shells have been found in their stomachs. But is it possible that tiger sharks could unintentionally attack surfers, mistaking them for turtles? David Silva thinks they might.

DAVID SILVA: We're out on the east side of the island of Kauai, on this beach called Wailua Beach. I got an attack off this point here, about seventy-five yards out from shore. To me, I think he thought that I was a turtle because my board is yellow, and with my hands paddling in the water, it makes me more look like a turtle. So I think he thought that I was a turtle, and he came for me.

JOE MORTON: David Silva was lucky. Other surfers have died in recent years from tiger shark attacks. He was badly hurt, but able to paddle his board safely to shore. For years, it was rare for a surfer to see a green turtle in the wild. Over-fishing had depleted their numbers, and their nesting beaches were destroyed by tourism. Today, surfers see turtles more often. But with some trepidation. It's widely believed that more turtles mean more shark attacks on people. The divers most accustomed to swimming with sea turtles are the marine biologists who monitor their survival in these waters. While the turtle population is rising, it is still at risk. The turtles are remarkably unwary of the scuba divers in their midst. On the sandy bottom, a mile off Honolulu, the scientists can catch the turtles by hand. The turtles are taken temporarily to a nearby boat for a physical exam. George Balazs is a research biologist with the National Marine Fisheries Service in Honolulu. He is not convinced of any link between turtles and sharks.

GEORGE BALAZS: Our research program started in 1972, twenty-two years ago. We have specifically gone to places in Hawaii that are the best sites for turtles, and in all those years of diving, we have never once, I have never once, encountered or even seen a tiger shark. One would think that if I am exposing myself to higher risk being with the turtles, that I would have at least seen one, and such has not been the case.

JOE MORTON: Balazs also doubts that tiger sharks mistake surfers for turtles.

GEORGE BALAZS: I think anybody that's in the ocean should have a healthy fear of sharks, but to think that they look like a turtle, I think there's no basis for it whatsoever. Any object in the water at or near the surface could be liable to be snapped at by a shark. You don't have to look like a turtle in order to be eaten by a predator.

JOE MORTON: So, if it's not a case of mistaken identity, are tiger sharks actively seeking human prey? The rate of attacks in Hawaii remains steady at about two per year, while the number of people in the water has sky rocketed. Biologist, Steve Kaiser believes this is proof enough.

STEVE KAISER: People aren't prey items for sharks. I mean you can look, these are what, potential victims here? No, you know, if people were being eaten by sharks all the time, if they were a natural prey item, we'd be getting ten attacks an hour. When you look at these people in the water, we are clumsy, we're awkward. Sharks are in their element and we're not. They would be taking these guys every minute of the day. I mean we are like fatted calves waiting to be slaughtered out there.

JOE MORTON: While rare, any shark attack can spur panic. In 1991, the state was shaken by the first confirmed fatality in three decades. The story led the news.

REPORTER: The waters off Olowalu, south of Lahaina, are normally calm. And forty-one-year-old, Martha Merrell, swam often near her beach front home. She had no warning that on the morning of November 26th, 1991, she would be killed by what was believed to be a fifteen foot tiger shark.

JOE MORTON: In the months that followed, there was a rash of five more attacks, two of them fatal.

REPORTER: His body board was found with a huge bite out of it—

JOE MORTON: With each attack, the outcry mounted.

REPORTER: After the attack, city and state officials closed beaches from Makawao to Makahuena until an effort can be made to find the killer shark.

JOE MORTON: Under pressure from the tourist industry, the state of Hawaii set up a task force to deal with the attacks. It went beyond closing beaches, they killed any tiger shark found in the area.

BRUCE CARLSON: Well as soon as people started, there were shark attacks that were happening and a few people were killed by sharks, there's a huge public outcry to do something about this situation.

JOE MORTON: After each attack, the state set fishing lines in the area. The goal was to hunt down the shark responsible for the terrifying incident. They carefully examined each carcass. But no human remains or other incriminating evidence were ever found.

BRUCE CARLSON: We were making a decision, if we're going to do any fishing, we're going to try and do it to make sure that we got the fish that actually was the cause of the attack. Otherwise, I don't think as biologists we'd just go out and randomly kill sharks to appease public opinion. It was our best guess that if we went within twenty-four hours, we might catch the shark that did it. We also know we need a lot more research to know about the biology of these animals to know what are the chances of actually catching that animal within twenty-four hours. Will it be there? Or won't it?

JOE MORTON: The State of Hawaii caught and killed eleven tiger sharks in all. Private fishermen thought it wasn't enough. They killed forty-four in a single year.

PERRY DANE: Every time there's an attack, the state takes out one or two sharks and they call it quits. So I want to just keep a consistent basis of bringing out sharks. If I can make a few bucks on it, hey. If fishing's slow, catch sharks, why not? If I'm not going to do it, who's going to do it?

JOE MORTON: The hunts calmed the public, but they also stirred controversy. Was the slaughter of these animals necessary? How many sharks would have to die to protect the beaches of Hawaii? To answer these questions, the state funded new research on tiger sharks. The principle investigator is Dr. Kim Holland of the Hawaii Institute of Marine Biology.

KIM HOLLAND: We don't know if the same fish come back to the same area day after day. We don't know if they have a home range that they patrol on a daily basis, or a weekly basis. We don't know if, what the size of that home range is, if there is one. We don't know if in fact there's just a continuous stream of new sharks coming past any given point on the shore line. And until you know those kinds of things about their movement patterns, any control mechanisms, or any control programs you might want to put in place, won't have any scientific direction to them.

JOE MORTON: This female tiger shark has been hooked on a line designed to inflict little injury. She is alive and well. But in a natural trance-like state. Merely flipping the shark on her back has induced this state, commonly called animal hypnosis. The shark makes no movement as Holland performs minor surgery, inserting a seven inch sonic transmitter into her belly. The transmitter has been coated with natural waxes to prevent an immune response. As soon as she is turned over, the shark snaps back to life, thrashing and struggling to break free. But first, someone has to take the hook out of her mouth.

KIM HOLLAND: One of the things we're finding is that these sharks have no qualms about going off-shore into deep blue water. One of the preconceptions was that these animals were coastal. This isn't the case at all.

JOE MORTON: This study is the first to track tiger sharks in the wild. The scientists drop an underwater antenna to listen for signals from the transmitter. It picks up signals from up to a mile away. The ship will stay on the trail for as long as the fuel, and the team's stamina, hold out, usually for forty-eight hours.

KIM HOLLAND: Well, as often is the case when you finally get the chance to see an animal or observe an animal in its own environment, you get surprises, things you didn't anticipate.

JOE MORTON: The common notion that tiger sharks patrol a small coastal area, that each shark has its own personal territory, is soon overturned. Instead, the researchers find the sharks travel great distances from island to island and dive as deep as a thousand feet.

KIM HOLLAND: We had no idea that these fish had this ability to go so deep so easily without apparently any restrictions on their movement patterns. So again, these are the kind of things that you can't find out without observing the animal in its own environment. And this is the first chance that we've had to do that with tiger sharks.

JOE MORTON: So far, Holland and his team have tagged over eighty tigers, from thousand-pound adults to sixty pound juveniles. Their work is the most extensive to date on the movement patterns of any large shark. Sometimes the researchers encounter and follow the same shark weeks or months after the initial track. The sonic transmitters last for about a year, which allows the team to look at whether tiger sharks return time and again to a specific location. At the spot where a tiger shark is originally caught, an underwater instrument is moored to the ocean floor. It serves as a listening post and records when and how often sharks revisit the site of their capture. Divers later retrieve the information which shows that sharks do return, and suggests that they may have home ranges. But the time between visits extends anywhere from a few weeks to a few months. Holland's tiger shark research, together with the countless hours he has spent with these animals, convince him that the sharks may have more to fear from human hunters than humans have to fear from them.

KIM HOLLAND: Well, one of the things we are finding in our research is it's not hard to catch tiger sharks. There's a lot of tiger sharks out there and there always has been. There also is a lot of people in the water in Hawaii, and they're very close together spatially. But we have very, very few shark attacks, maybe less than two per year, state wide. These sharks are not careless about what they do. People are not a normal part of their diet, even if they were just biting anything that was more or less in the right place at the right time, we would have dozens of attacks on people in a month. But we don't. And this indicates to me that these sharks are not careless. They are very specific about what they eat and people are not one of those things.

JOE MORTON: In the effort to prevent shark attacks, Holland's work holds an important lesson. Attempts to hunt down specific killer sharks may be in vain, because tiger sharks range so widely. The shark responsible is likely long gone and any sharks killed will probably be replaced by others. A single hunting shark can cover a huge area, from Oahu, for example, to a group of sand atolls five hundred miles away. This pristine underwater wilderness is rich with marine life, the area, part of the northwestern islands of Hawaii, is a wildlife preserve where commercial fishing is outlawed. Surrounded by shallow water teaming with fish, the islands are ideal for seabirds. More than fourteen million birds of fifteen different species migrate here to nest. And tiger sharks come the same time each year to prey on the offspring. Albatross chicks are the primary target. These babies will grow rapidly on a diet of regurgitated fish. By mid-June, they will be fed less and less often. Soon, their parents will leave the island, and the chicks will be on their own. Each morning, when the wind rises, they face into it and exercise their flying muscles. There is one last feeding and then the fledglings will have to find their own fish. They make their way into the water and face the dangers that await them. All around them, dark shadows move beneath the surface. Catching winged prey is a test of a great hunter's prowess. The first fledglings to venture from their nests stay close to the shore. The sharks are hungry, but they must maneuver in water only a few feet deep. Over the first few days, the sharks find it difficult to come to grips with their prey. They're out of practice. They haven't tried to catch albatross chicks since this time last year. The chick fights back, pecking at its tormentor, instinctively aiming for the shark's most vulnerable spot, its eyes. The tiger has a natural defense, a lower eye lid that closes as the shark lunges forward toward its prey. During these first few critical days, some chicks learn to fly in time to escape. But the tiger sharks cruising these waters have other options. The northwestern islands are the breeding ground of the Hawaiian monk seal, an endangered species rare around the main islands. There are only about fourteen hundred of them. For tigers, as for great whites, marine mammals are a source of energy-rich blubber. Some of these seals have bite scars and missing flippers and keep a sharp look out for sharks. But at this time of year, the tigers may be less interested in seals than usual. For days on end, albatross chicks have been testing their skills on the open beach where the breeze is strongest. Once on the wing, they might not return to the islands for three years, if they survive that long. The sharks have also been practicing. They now know that they must reach high out of the water to be sure of catching the bird. If it misses on the first strike, the shark turns and follows the chick upwind. Eventually, the young muscles tire, and the bird is trapped. About one in ten chicks falls victim to sharks each year. More die of starvation or drown in the surf. In a matter of weeks, the birds are gone, and the tiger sharks swim off as well to seek better hunting grounds elsewhere. Legend says it is folly to play in the surf around sunrise or sunset, that this is the time when sharks come to feed. Like other folklore, this belief is being overturned. Tiger sharks may be in these waters at all times, but they are not here to hunt humans. If sharks were man-hunters, surfing would be suicide. These animals are powerful, adaptable hunters, occupying their rightful place in the ocean. It is up to us to stay out of their way.

JOE MORTON: Shark bites don't hurt if they're digital. Dive into NOVA's web site for a virtual swim with these master predators of the deep at pbs.org. To order this show for $19.95 plus shipping and handling, call 1-800-949-8670. And, to learn more about how science can solve the mysteries of our world, ask about our many other NOVA videos.

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