- 5/18/2025
Strong and deadly, silent and swift, insatiable in its hunger for flesh – there is no more powerful image in nature than that of the shark. And chief among these emblems of terror are the Great White and the Tiger Shark. We will explore the behavior of these great killing machines of the seas and the attitudes of people towards them – from those who would see all sharks wiped out, to those others whose fear is tempered with awe, and even religious respect. Shot at exotic locations in California, Hawaii and Australia, the film looks at the dramatic increase in shark attacks on humans in the last few years. Is there a reason surfers are particularly vulnerable? We investigate the occurrence of attacks and the reason for their increase – with spectacular footage of sharks in action.
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TVTranscript
00:00Tonight on NOVA, all I could see really was the teeth out of my left eye.
00:06Frightening.
00:07Folded me in half so quickly I didn't have any idea what was going on.
00:11Formidable.
00:12And the water was turning all dark around me with blood.
00:17Unforgiving.
00:18Holy smokes.
00:19But are sharks really man hunters?
00:21Science takes a hard look at one of our greatest fears.
00:58The clear blue waters and rolling surf of the California coast are a playground in the sun.
01:13They are also the hunting ground of one of the world's most dangerous creatures.
01:19The great white shark.
01:24Encounters between sharks and surfers are rare, but unforgettable.
01:36They strike with no warning, and little chance of escape.
01:42When it first hit me it was such a hard blow, I mean it really hit hard.
01:54Held in the jaws of a 15 foot shark, Kirk Johnson thought it was the end.
02:02He felt his body shaking violently.
02:07But as quickly as it began, the attack was over.
02:13And the shark, it just let go of me.
02:15And I came to the surface, and the water was turning all dark around me with blood.
02:23His back torn open, Johnson was barely able to get to shore.
02:30Why did the shark attack, and then suddenly release him?
02:40Surfer John Ferrara has asked the same question.
02:46While paddling his board, Ferrara was hit by an immense force.
02:52I describe it as about the size of a Volkswagen, the body of it, just the girth.
02:58The fin of it was about three feet out of the water while it was just going past me very slowly.
03:04And you pretty much know exactly what it is.
03:07It's something wanting to eat you, you know, and you want to get the hell out of there.
03:14But if the shark had wanted to eat John Ferrara, why didn't it?
03:21Like surfers who are attacked, both men escaped and returned to the water as soon as they could.
03:31Some believe surfers are tempting fate.
03:36But is the great white shark really a manhunter?
03:44The elusiveness of these sharks has shrouded them in mystery.
03:48Yet new research sheds light on why attacks happen.
03:53As science replaces sensationalism, these sharks may lose their reputation as monsters of the deep.
04:07To understand sharks, researchers must delve into their domain.
04:14The Farallon Islands lie just 20 miles off the coast of California, west of San Francisco.
04:24In Native American legend, their sinister, jagged peaks were said to be the islands of the dead.
04:34The Farallons are also a regular feeding area of the great white shark.
04:44There are few places in the world where great whites can be so closely observed in the act of killing.
04:59Their prey are usually marine mammals, like these California sea lions.
05:06Some members of this group have had narrow escapes.
05:15But they are not the only animals facing danger.
05:19In the fall, the presence of northern elephant seals ushers in the hunting season.
05:26It's a busy time for biologists like Peter Pyle, who spends much of the year studying birds.
05:33Now he turns to pinnipeds, seals and sea lions, and the sharks that prey on them.
05:46California sea lions haul out here to rest throughout the year.
05:52Safe on the shore, but often enduring plagues of flies.
06:03In the autumn, they are joined by juvenile elephant seals coming ashore for the first time in months.
06:13The seasonal concentration of young, naive seals draws white sharks.
06:22Like a magnet.
06:30Hauling out on this rocky ledge is a struggle, especially at high tide.
06:36Huge waves can wash the seals right back into the surf.
06:44Just a few feet offshore, the sharks are waiting for them.
06:50And Peter Pyle is waiting for the sharks.
06:56Shark is a visual predator, white shark here, more than anything.
07:00It stalks in the depths, probably behind ridges, against the rocks, where the pinnipeds are going to have a harder time seeing it.
07:07And then when the time's right, it'll rush up from below and strike the pinniped at the surface.
07:19Stealth and surprise are critical elements in a successful attack.
07:50The blood slick and agitated sea lions are ready to strike.
07:56They're ready to strike.
08:00They're ready to strike.
08:04They're ready to strike.
08:08They're ready to strike.
08:12They're ready to strike.
08:17The blood slick and agitated gulls draw the attention of the Farallon researchers, waiting at a vantage point high on the island.
08:29To understand more about where and how sharks attack, the researchers need to pinpoint the location.
08:36They will later visit this site to check the water depth and clarity, and whether the kill takes place over rock or a sandy bottom.
08:48But now, they want to observe the feeding while it's happening.
08:53Pyle hurries to the boat landing.
08:58There he joins shark biologist Scott Anderson.
09:07If it's a big seal, it may take the shark half an hour to eat it.
09:11This gives the team time to get on the water and alongside the kill.
09:17Rough seas make their job more difficult.
09:21Their boat is only 14 feet long.
09:25The first couple of times we went out in boats, we approached it very cautiously.
09:30We circled in, we kept our distance, we looked from a distance, we took pictures from a distance.
09:35And then slowly we realized that the sharks would come up to the boat, but they didn't have any real intention on doing anything.
09:42They were more or less just checking us out.
09:45It's very exciting to see a shark in the water.
09:48These sharks are huge, you know, we're talking 15 to 18 feet, with a weight of maybe 3 to 4,000 pounds.
09:55And they have an amazing presence in the water.
09:58As they move through the area, they're very controlled.
10:01They know where they're going before they get there.
10:03And so you just are kind of in awe of this silent, huge predator moving through the water.
10:13At the attack site, the two men lower underwater cameras beside the boat.
10:20Other sharks may move in to get a bite of the prey.
10:23But if the killer is a big animal, they stay away.
10:31Scars on their skin suggest great whites may at times turn on one another.
10:41We're out there getting as much video as we can on these sharks.
10:45And a lot of them have scars of various types.
10:48Some 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.
10:55A lot of the females seem to have scars along the gills, which may relate to mating scars.
11:00And these scars are pretty permanent.
11:03They look white at first, and then they turn black.
11:05And after a while, we'll mark down all the spots where these scars are.
11:09And we'll be able to use those in our individual ID.
11:15Scott Anderson has identified more than 40 white sharks here.
11:22Many return, time and again.
11:31After the initial violent attack, sharks feed in a controlled, almost calm manner, contrary to the notion of a feeding frenzy.
11:44A shark can consume a 400-pound meal in 10 immense bites of up to 50 pounds each.
11:53The Farallon researchers are accustomed to sharing these waters with feeding sharks.
11:58They witness up to 70 attacks each season.
12:05Still, working in a boat that is smaller than the sharks that surround it takes courage.
12:13It's always a thrill when you've got white sharks circling around below you.
12:18I don't think we'll ever get over that thrill.
12:21They're looking at us. They're curious.
12:23It's interesting in that the biggest ones seem to be the smartest about it
12:27and know sooner that we're not edible and disappear quicker.
12:32It's actually the little ones that we're a little more worried about,
12:35maybe the 9 to 12-footers that we see here, because they're less experienced.
12:39We don't know what they're going to do.
12:41They're less predictable, as far as I'm concerned.
12:43They're the ones that may be the most vulnerable.
12:46As far as I'm concerned, they're the ones that may end up getting a little excited near the boat.
12:50I think they're also the ones that might be hitting surfers more.
12:58Surfers are more vulnerable to great white sharks than anyone else in the water.
13:08As they skim the surface of the waves, underneath them, sharks may be lurking.
13:17But their presence here may have little to do with seeking human prey.
13:25Many of the best surfing beaches are near the breeding colonies of seals and sea lions.
13:32In 50 years, there have been fewer than 80 attacks on humans in California, only 7 fatal.
13:41With so many people in the water, it's surprising there haven't been more.
13:50Perhaps the attacks that do take place are cases of mistaken identity.
13:58A surfer paddling out to sea, arms waving and feet trailing, may look like a seal.
14:07But even if they look like the favorite food of great whites, surfers don't taste the same.
14:17Compared to an elephant seal, a human body must seem bony.
14:24The scars on animals here at Ananuevo, south of the Farallones, testify to their shark encounters.
14:42Seals and sea lions have been the prey of large sharks for some 35 million years.
14:54Ferocious as these male elephant seals may be, they are no match for sharks.
15:02As females look on, bulls, over three times their weight, fight for mating rights.
15:12Protection of breeding colonies like this one has brought seal populations back from the edge of extinction.
15:24Forty years ago, this beach was barren. Now, it is home to over 10,000 animals.
15:33It is literally a pup factory.
15:54But as soon as these babies are weaned, they will have to leave the beach and start to feed themselves.
16:04It will be months before they see land again.
16:10Many of those feeding contentedly at their mother's sides,
16:14will find themselves in the shark-infested waters of the Farallone Islands, seeking shelter on the wave-swept rocks.
16:30It happens every fall, and the biologists will be waiting.
16:37Scott Anderson has studied great whites for nearly 10 years,
16:41and has a down-to-earth view of the drama between predator and prey.
16:47The great white shark is an apex predator that feeds on marine mammals.
16:52When they're young, they feed on fish. As they grow older, they begin feeding on strictly marine mammals.
16:57And that puts them at the top of the food chain.
17:01The elephant seals are considered to be the preferred prey at the Farallones,
17:06in that they're solitary animals, they're easy to capture because they're slow swimmers,
17:11and they tend to be naive when they're young, and they sit at the surface, which they shouldn't do.
17:23As it patrols beneath the waves, the shark can see the silhouettes of prey above.
17:31Great whites cruise 60 to 100 feet underwater,
17:36close enough to maintain eye contact, yet far enough to ensure stealth.
17:45Sea lions are attacked far less often than elephant seals, perhaps because they travel in groups,
17:51with more pairs of eyes on the lookout for danger.
17:57These warm-blooded mammals are swift and agile, and difficult for sharks to catch.
18:07The great white's hydrodynamic design is adapted more for cruising than sustained sprints.
18:14But it is equipped for short, high-speed dashes, propelled by an awesomely powerful tail.
18:23The slow-moving elephant seal doesn't stand a chance.
18:34The shark rushes up from the bottom in an ambush attack.
18:40A lethal first bite ensures the seal can't fight back.
18:58The seal dies quickly, but it's not the end of the story.
19:09The great white dies quickly from loss of blood,
19:14while the shark thrashes its head back and forth, cutting through muscle, bone and blubber.
19:29It's a bite that requires the powerful jaw of an adult great white, as biologist Ken Goldman explains.
19:39It's a bite that requires the powerful jaw of an adult great white, as biologist Ken Goldman explains.
20:10The teeth are pointed back in, giving grip. The top teeth then come down and are removing that bite.
20:21The infamous jaws of the great white shark are remarkable in other ways.
20:27Its upper jaw is not firmly joined to the skull, but can jut forward to clamp down on prey.
20:34And the shark has a seemingly endless supply of fresh, sharp teeth.
20:40When front teeth are damaged, back ones move forward to replace them.
20:46A shark may grow and discard thousands of teeth in its lifetime.
20:55Great whites may live up to 70 years, but this, like much about the shark,
21:01is still uncertain.
21:06They have been captured, but never successfully kept in captivity.
21:12Their movement and behavior in the wild is now better understood thanks to remote tracking.
21:18The tracking of sharks out at the Farallones consists of feeding a shark one of these.
21:24This is a sonic transmitter, and it relays temperature and swimming depth of the animal to me.
21:30This seal will go out in the boat and put this in the water with a small piece of seal or sea lion blubber.
21:36And the shark ingests this, we're able to start tracking immediately.
21:40It's done within the natural predatory sequence.
21:48Goldman finds that large individuals tend to feed in the same place each year,
21:54patrolling areas where they have been successful before.
22:01Younger, less experienced sharks move around the islands looking for chance encounters with prey.
22:11The transmitters also show that the body temperature of great white sharks
22:16is much higher than that of the surrounding water.
22:20And, like warm-blooded mammals, the shark maintains a constant internal temperature.
22:26It's probably a very effective, evolved mechanism for these animals.
22:29This is an animal that is an active hunter in very cool water conditions,
22:33and it's hunting a very swift and agile prey.
22:35So, my hypothesis is that if the animal was not regulating its body core temperature,
22:39being much higher than water temperature, it would probably not be an effective hunter.
22:46Being warm-blooded also helps the shark to digest blubber, a very rich source of energy.
22:53And no prey offers more blubber than a whale.
23:03The great whales, like these humpbacks, may have once been important to the shark's diet.
23:10Now, these whales are scarce.
23:14And to find a carcass washed up on a beach is a rare treat for a foraging shark.
23:23If there is one to be found, the shark's acute sense of smell will detect it even from miles away.
23:30If there is one to be found, the shark's acute sense of smell will detect it even from miles away.
23:39This humpback whale will provide a huge meal, hundreds of pounds of blubber.
23:48The challenge for the shark is to find the proper angle to take a bite out of the massive carcass.
24:00A meal like this can sustain a great white for over a month.
24:08But scavenging whales is not a reliable source of food.
24:13A large predator must have easy access to living prey, as the great white shark has at the Farallones.
24:22In these rough waters, where seals abound, Scott Anderson has devised a way to get a whole new view of a shark attack.
24:31He attaches a video camera to a board.
24:34Research shows that this particular shape will provoke great whites.
24:43Scott and Peter Pyle motor out to a place they know is teeming with sharks.
24:48Remarkably, no animal bait is needed to attract the sharks.
24:52They are drawn simply by the shape of the board, oblong and roughly six feet in length,
24:58the shape of a seal, a sea lion, or a floating surfer.
25:03Sometimes, the sharks merely investigate the board and swim by.
25:10But at other times, they stalk and attack.
25:18In this particular video, Scott and Peter Pyle take a closer look at the shark.
25:24Following the initial strike, the sharks may hover momentarily,
25:28but they rarely return to the surface.
25:32Following the initial strike, the sharks may hover momentarily, but they rarely return
25:53for a second bite.
25:56They know a good thing when they taste it, and this isn't it.
26:04The fierceness of this attack startles even the most unflappable scientist.
26:10Last year I was scared by a shark that came up to investigate the board that I had out
26:16when it was really close to the boat, actually bringing it into the boat about a foot away.
26:20When the shark attacked it, it went violently through the area, incredibly quick, incredibly
26:26loud, and it really scared me.
26:28So it made me realize that there are certain times when dealing with these animals where
26:32there is some danger.
26:33But most of the time when they're around the boat, they're very controlled, they're looking
26:36for food, and it usually seems pretty safe to me for the most part.
26:42It's safe, for the most part, for other people working at the Farallones.
26:47Many fishermen collecting highly prized shellfish.
26:57Climbing into waters inhabited by great whites may seem a questionable practice, but even
27:05here the risk of attack is slim.
27:11Ninety percent of shark attacks take place at the surface, most others in midwater.
27:20On the seafloor, divers are relatively safe.
27:31But diving with open wounds, or holding fish and other bait, is asking for trouble.
27:49The divers must keep a sharp lookout for cruising great whites, as they measure the abalone
27:54to make sure they meet legal standards.
28:02Rod Orr holds the dubious distinction of having been attacked twice in pursuit of abalone.
28:09Just at the edge of vision, I saw something, but I didn't realize what it was, and then
28:13the little light dawned, and all I could see was the gills on this white shark, and the
28:18shark was like 10, 11 foot long, and it closed on me, and when I looked back at it, it closed
28:23the distance by half, and then it started coming in fast, and I knew it was after me,
28:28but I tried to get behind this rock, and when I tried to get behind it, the shark came in
28:32on my left side, his mouth just opened up, and his jaw actually just came out of his
28:37mouth, and I had a roll of teeth marks up in my scalp where he bit down, and the worst
28:42damage was probably to my nose and to my lower eye, because I had a hole through the upper
28:46eyelid and the bottom eyelid.
28:48All I could see was really was the teeth out of my, you know, from my left eye, I could
28:53see the water down there, and I could see all the teeth in the top jaw and the bottom
28:57jaw, but I was face down in it, and it was just like, they looked huge, they looked like
29:02they were three inches long, I know they weren't that big, but they were just all white, and
29:05I could see about, I could see about 10 or 12 teeth.
29:09I think he realized that I wasn't a seal at that time, but why he didn't finish biting
29:13the head off, and why he didn't thrash, I don't know, just luck of the draw.
29:20Why did the shark release him?
29:22Most likely, a bony human didn't seem a worthwhile meal.
29:27But there are sharks in other parts of the world with less discriminating tastes.
29:34Perhaps these predators are even more to be feared.
29:43In tropical waters throughout the world, including here in Hawaii, there lives a shark responsible
29:49for more attacks on humans than even the great white.
29:57In a place of golden beaches, where surfing is a way of life, more people are exposed
30:03to danger.
30:07These clear and inviting waters are also home to the tiger shark.
30:14As the largest shark on most Pacific reefs, tigers rule as apex predators, feeding on
30:22fish and lobsters, seals and turtles, rays and other sharks.
30:29They are said to eat just about anything that comes their way, floating license plates,
30:36garbage from ships, even humans.
30:45Hawaiian culture has a special word for sharks that eat people, ni'ui.
30:51They are animals both feared and respected.
30:56Local surfers today reassure themselves in different ways about the dangers of shark-infested
31:02waters.
31:03I'm not worried about the tiger shark because I feel like that's my alma cua, which means
31:09it's a religious belief that native Hawaiians have about the sharks.
31:14It depends. If there's a lot of people around, I don't worry about it too much because the
31:19odds of getting eaten is probably a little less, but when you go surfing other secret
31:24spots and stuff, that's when you're always looking down, checking it out.
31:28If you were to go surfing, go snorkeling when it's flat, you'd see a million turtles, and
31:32that's what the tiger sharks eat.
31:35Marine turtles are common in the tiger shark's diet.
31:39Whole shells have been found in their stomachs.
31:43But is it possible that tiger sharks could unintentionally attack surfers, mistaking
31:50them for turtles?
31:53David Silva thinks they might.
31:58We're at, on the east side, on the island of Kauai, at this beach called Wailua Beach.
32:03I got attacked off this point here, about 75 yards out from shore.
32:08To me, I think he thought that I was a turtle because my board is yellow, and with my hands
32:13paddling in the water, it makes me more look like a turtle.
32:17So I think he thought that I was a turtle and he came for me.
32:24David Silva was lucky.
32:26Other surfers have died in recent years from tiger shark attacks.
32:31He was badly hurt, but able to paddle his board safely to shore.
32:47For years, it was rare for a surfer to see a green turtle in the wild.
32:53Overfishing had depleted their numbers, and their nesting beaches were destroyed by tourism.
33:07Today, surfers see turtles more often, but with some trepidation.
33:13It's widely believed that more turtles mean more shark attacks on people.
33:23The divers most accustomed to swimming with sea turtles are the marine biologists who
33:29monitor their survival in these waters.
33:35While the turtle population is rising, it is still at risk.
33:43The turtles are remarkably unwary of the scurrying waves.
33:49The turtles are remarkably unwary of the scuba divers in their midst.
34:01On the sandy bottom, a mile off Honolulu, the scientists can catch the turtles by hand.
34:09The turtles are taken temporarily to a nearby boat for a physical exam.
34:27George Ballas is a research biologist with the National Marine Fisheries Service in Honolulu.
34:33He is not convinced of any link between turtles and sharks.
34:40Our research program started in 1972, 22 years ago.
34:45We have specifically gone to places in Hawaii that are the best sites for turtles.
34:51And in all those years of diving, I have never once encountered or even seen a tiger shark.
34:57One would think that if I'm exposing myself to higher risk, being with the turtles,
35:02that I would have at least seen one, and such has not been the case.
35:07Ballas also doubts that tiger sharks mistake surfers for turtles.
35:12I think anybody in the ocean should have a helping fear of sharks,
35:17but to think that they look like a turtle, I think, is no basis for it whatsoever.
35:22Any object in the water, at or near the surface, could be liable to be snapped at by a shark.
35:27You don't have to look like a turtle in order to be eaten by a predator.
35:31So, if it's not a case of mistaken identity, are tiger sharks actively seeking human prey?
35:41The rate of attacks in Hawaii remains steady at about two per year,
35:46while the number of people in the water has skyrocketed.
35:51Biologist Steve Kaiser believes this is proof enough.
35:56People aren't prey items for sharks.
35:59I mean, look, these are, what, potential victims here?
36:03No, you know, if people were being eaten by sharks all the time,
36:08if they were our natural prey items, we'd be getting ten attacks an hour.
36:12When you look at these people in the water, we are clumsy, we're awkward.
36:17Sharks are in their element, and we're not.
36:20They would be taking these guys every minute of the day.
36:24I mean, we are like fatted calves waiting to be slaughtered out there.
36:31While rare, any shark attack can spur panic.
36:35In 1991, the state was shaken by the first confirmed phenomenon.
36:40The state was shaken by the first confirmed fatality in three decades.
36:44The story led the news.
36:48The waters off Olawalo, south of Lahaina, are normally calm,
36:52and 41-year-old Martha Morrell swam off and near her beachfront home.
36:55She had no warning that on the morning of November 26, 1991,
36:59she would be killed by what was believed to be a 15-foot tiger shark.
37:05In the months that followed, there was a rash of five more attacks.
37:10But two of them fatal.
37:12His body board was found with a huge bite out of it.
37:14With each attack, the outcry mounted.
37:17After the attack, city and state officials closed beaches from Makaha to Makua
37:21until an effort could be made to find the killer shark.
37:26Under pressure from the tourist industry,
37:29the state of Hawaii set up a task force to deal with the attacks.
37:35Kaiser is the same man who just two weeks ago...
37:37Beyond closing beaches, they killed any tiger shark found in the area.
37:41Kaiser said the drill is the same this time around.
37:44Well, as soon as people started...
37:46There were shark attacks that were happening,
37:48and a few people were killed by sharks.
37:50There's a huge public outcry to do something about this situation.
37:55After each attack, the state set fishing lines in the area.
37:59The goal was to hunt down the shark responsible for the terrifying incident.
38:08They carefully examined each carcass.
38:11But no human remains or other incriminating evidence were ever found.
38:17We were making a decision, if we're going to do any fishing,
38:20we're going to try and do it to make sure that we got the fish
38:23that actually was the cause of the attack.
38:25Otherwise, I don't think as biologists,
38:27we'd just go out and randomly kill sharks to appease public opinion.
38:30It was our best guess that if we went within 24 hours,
38:33we might catch the shark that did it.
38:35We also know we need a lot more research to know about the biology of these animals
38:39to know what are the chances of actually catching that animal within 24 hours.
38:43Will it be there or won't it?
38:47The state of Hawaii caught and killed 11 tiger sharks in all.
38:52Private fishermen thought it wasn't enough.
38:55They killed 44 in a single year.
38:59Every time there's an attack,
39:01the state takes out one or two sharks and they call it quits.
39:04So I want to just keep a consistent basis of bringing out sharks.
39:08If I can make a few bucks on it,
39:10just fishing slow, get sharks, why not?
39:13If I'm not going to do it, who's going to do it?
39:18The hunts calmed the public, but they also stirred controversy.
39:24Was the slaughter of these animals necessary?
39:28How many sharks would have to die to protect the beaches of Hawaii?
39:35To answer these questions,
39:37the state funded new research on tiger sharks.
39:40The principal investigator is Dr. Kim Holland
39:44of the Hawaii Institute of Marine Biology.
39:48We don't know if the same fish come back to the same area day after day.
39:52We don't know if they have a home range that they patrol
39:55on a daily basis or a weekly basis.
39:57We don't know what the size of that home range is, if there is one.
40:01We don't know if, in fact, there's just a continual stream of new sharks
40:05coming past any given point on the shoreline.
40:08Until you know those kinds of things about their movement patterns,
40:11any control mechanisms or any control programs you might want to put in place
40:16won't have any scientific direction.
40:18This female tiger shark has been hooked on a line
40:22designed to inflict little injury.
40:24She is alive and well, but in a natural trance-like state.
40:31Merely flipping the shark on her back has induced this state,
40:35commonly called animal hypnosis.
40:42The shark makes no movement as Holland performs minor surgery,
40:46inserting a 7-inch sonic transmitter into her belly.
40:50The transmitter has been coated with natural waxes
40:53to prevent an immune response.
40:57As soon as she is turned over, the shark snaps back to life,
41:02thrashing and struggling to break free.
41:06But first, someone has to take the hook out of her mouth.
41:19One of the things we're finding is that these sharks have no qualms
41:22about going offshore into deep blue water.
41:25One of the preconceptions was that these animals were coastal.
41:28This isn't the case at all.
41:34This study is the first to track tiger sharks in the wild.
41:43The scientists drop an underwater antenna
41:46to listen for signals from the transmitter.
41:50It picks up signals from up to a mile away.
41:54The ship will stay on the trail for as long as the fuel
41:57and the team's stamina hold out,
42:00usually for 48 hours.
42:09Well, as often is the case, when you finally get a chance to see an animal
42:13or observe an animal in its own environment,
42:15usually we get surprises, things we didn't anticipate.
42:18The common notion that tiger sharks patrol a small coastal area,
42:22that each shark has its own personal territory,
42:25is soon overturned.
42:28Instead, the researchers find the sharks travel great distances
42:32from island to island and dive as deep as 1,000 feet.
42:37We had no idea that these fish had this ability to go so deep so easily
42:41without apparently any restrictions on their movement patterns.
42:44So, again, these are the kind of things that you can't find out
42:47without observing the animal in its own environment,
42:50and this is the first chance that we've had to do that with tiger sharks.
42:59So far, Holland and his team have tagged over 80 tigers,
43:07from 1,000-pound adults to 60-pound juveniles.
43:14Their work is the most extensive to date
43:16on the movement patterns of any large shark.
43:22Sometimes the researchers encounter and follow the same shark
43:25weeks or months after the initial track.
43:32The sonic transmitters last for about a year,
43:35which allows the team to look at whether tiger sharks return
43:39time and again to a specific location.
43:47At the spot where a tiger shark is originally caught,
43:50an underwater instrument is moored to the ocean floor.
43:55It serves as a listening post
43:58and records when and how often sharks revisit the site of their capture.
44:05Divers later retrieve the information,
44:08which shows that sharks do return
44:11and suggest that they may have home ranges.
44:15But the time between visits extends anywhere
44:18from a few weeks to a few months.
44:23Holland's tiger shark research,
44:26together with the countless hours he has spent with these animals,
44:30convince him that the sharks may have more to fear from human hunters
44:34than humans have to fear from them.
44:38One of the things we're finding in our research
44:40is it's not hard to catch tiger sharks.
44:42There's a lot of tiger sharks out there, and there always has been.
44:45There also is a lot of people in the water in Hawaii,
44:48and they're very close together spatially.
44:50But we have very, very few shark attacks,
44:52maybe less than two per year statewide.
44:55These sharks are not careless about what they do.
44:58People are not a normal part of their diet.
45:00Even if they were just biting anything
45:02that was more or less in the right place at the right time,
45:05we have dozens of attacks on people in a month, but we don't.
45:09And this indicates to me that these sharks are not careless.
45:12They're very specific about what they eat,
45:14and people are not one of those things.
45:18In the effort to prevent shark attacks,
45:21Holland's work holds an important lesson.
45:27Attempts to hunt down specific killer sharks may be in vain
45:32because tiger sharks range so widely.
45:36The shark responsible is likely long gone,
45:39and any sharks killed will probably be replaced by others.
45:45A single hunting shark can cover a huge area,
45:49from Oahu, for example,
45:51to a group of sandy atolls 500 miles away.
46:00This pristine underwater wilderness is rich with marine life.
46:05The area, part of the northwestern islands of Hawaii,
46:09is a wildlife preserve where commercial fishing is outlawed.
46:18Surrounded by shallow water teeming with fish,
46:22the islands are ideal for seabirds.
46:29More than 14 million birds of 15 different species
46:33migrate here to nest.
46:42And tiger sharks come the same time each year
46:46to prey on the offspring.
46:54Albatross chicks are the primary target.
46:58These babies will grow rapidly on a diet of regurgitated fish.
47:05By mid-June they will be fed less and less often.
47:10Soon their parents will leave the island
47:13and the chicks will be on their own.
47:19Each morning, when the wind rises,
47:21they face into it and exercise their flying muscles.
47:28There's one last feeding,
47:30and then the fledglings will have to find their own fish.
47:38They make their way into the water
47:40and face the dangers that await them.
47:51All around them, dark shadows move beneath the surface.
47:57They can't see.
48:17Catching winged prey is a test of a great hunter's prowess.
48:28The first fledglings to venture from their nests
48:31stay close to the shore.
48:35The sharks are hungry,
48:37but they must maneuver in water only a few feet deep.
48:43Over the first few days,
48:45the sharks find it difficult to come to grips with their prey.
48:52They're out of practice.
48:55They haven't tried to catch albatross chicks
48:58since this time last year.
49:05The chick fights back, pecking at its tormentor,
49:09instinctively aiming for the shark's most vulnerable spot,
49:13its eyes.
49:18The tiger has a natural defense,
49:21a lower eyelid that closes as the shark lunges forward toward its prey.
49:32During these first few critical days,
49:35some chicks learn to fly in time to escape.
49:42But the tiger sharks cruising these waters have other options.
49:48The northwestern islands are the breeding ground of the Hawaiian monk seal,
49:53an endangered species rare around the main islands.
49:58There are only about 1,400 of them.
50:04For tigers, as for great whites,
50:07marine mammals are a source of energy-rich blubber.
50:11Some of these seals have bite scars and missing flippers
50:14and keep a sharp lookout for sharks.
50:18But at this time of year,
50:20the tigers may be less interested in seals than usual.
50:27For days on end,
50:29albatross chicks have been testing their skills on the open beach
50:33where the breeze is strongest.
50:35Once on the wing, they might not return to the islands for three years,
50:39if they survive that long.
50:42The sharks have also been practicing.
51:06They now know that they must reach high out of the water
51:10to be sure of catching the bird.
51:28If it misses on the first strike,
51:31the shark turns and follows the chick upwind.
51:46Eventually, the young muscles tire and the bird is trapped.
52:02About one in ten chicks falls victim to sharks each year.
52:08More die of starvation or drown in the surf.
52:14In a matter of weeks, the birds are gone
52:17and the tiger sharks swim off as well
52:20to seek better hunting grounds elsewhere.
52:32Legend says it is folly to play in the surf around sunrise or sunset,
52:37that this is the time when sharks come to feed.
52:41Like other folklore, this belief is being overturned.
52:46Tiger sharks may be in these waters at all times,
52:50but they are not here to hunt humans.
52:53If sharks were man hunters, surfing would be suicide.
53:00These animals are powerful, adaptable hunters
53:04occupying their rightful place in the ocean.
53:10It is up to us to stay out of their way.
53:23Shark Bites
53:47Shark Bites don't hurt if they're digital.
53:50Dive into NOBA's website for a virtual swim
53:53with these master predators of the deep
53:56at pbs.org
54:12To order this show for $19.95 plus shipping and handling
54:16call 1-800-255-9424
54:21And to learn more about how science can reveal the truth
54:24and solve the mysteries of our world
54:27ask about our many other NOVA videos.
54:33Next time on NOVA
54:35Breakthrough microphotography reveals the exquisite diversity of life on Earth
54:40and the surprising threads that connect us to a common ancestry.
54:45From the photographer who first captured the miracle of life
54:48a three part special, Odyssey of Life.
55:02NOVA is a production of WGBH Boston.
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