The Strange Behavior Of The World's Biggest Shark

This is the biggest fish in the planet's oceans and also our greatest shark. Yet it's an enigma. Much of its life cycle still remains a mystery to science and a recently discovered relationship with man has only heightened the intriguing puzzles researchers are attempting to unravel. Cenderawasi Bay in the Indonesian province of Papua on the island of New Guinea. One of the planet's final frontiers. Something strange and wondrous is happening here that occurs nowhere else. On a lonely fishing pontoon in one of the remotest bays in the ocean, a unique bond has evolved between the sea's greatest fish and a group of simple Indonesian fishermen. Every day the fishermen haul nets full of silver bait fish. Those they don't need are discarded but by throwing the excess overboard the fishermen discovered a new customer. One that has become their friend, a good omen and sometimes their playmate. Every day the giant shark queue up to share the catch. Hanging vertically in the water, they suck fish from the nets. Far from regarding them as a nuisance, the fishermen believe the shark bring luck and feed them morsels to encourage them to stay around. I think of the whale shark as a friend. We cooperate with them. If we don't bother them, they don't bother us. This relationship between giant shark and Papuan fishermen has only just been discovered and is yet another piece in the confusing jigsaw puzzle of our knowledge of them. Because so much of the whale shark's life remains a mystery, an enigma to science. We've no idea where they mate, where the females give birth and where the newborn sharks spend the first years of life. Though they grow as long as a school bus and can weigh even more, much of the life cycle of the planet's greatest fish is shrouded in mystery. Tracking the shark has disclosed that they make seemingly inexplicable ocean journeys. Why? And now this apparent aberration in the behaviour of these giant shark has been discovered that turns on its head all we thought we knew and understood about them. Half a world away from the tranquility of Papua lies Isla Mujeres, a small island off Mexico's Yucatan Peninsula. Busy and built up, a tourist Mecca, Isla Mujeres is also home to an incredible natural phenomenon. It's an area of strong offshore currents and upwellings from the deep, created by the meeting of the waters of the Gulf of Mexico and the Caribbean Sea. And between May and September each year, it's home to what's believed to be the largest feeding aggregation of whale sharks in the world. Around 1,500 and maybe even more gather here to take advantage of a natural rather than a man-made feeding opportunity. And there's plenty to feed on. Every year, snappers spawn in their millions off the coast of Mexico and every year the whale shark aggregate to feed on the eggs drifting in the plankton. Because despite their immense size, whale shark feed only on the tiniest creatures in the ocean. Unlike the whale shark in Papua, these are behaving in a more expected and natural way. Cruising with their mouths wide open, the shark strain plankton and small fish from the water. But intriguingly, these are all young shark. Why are the adults not here to join in this feeding bonanza? Indeed, where are those adults? Except when we see them in mass aggregations like this, little is known of the remainder of their lives. The ocean's vast and even such huge creatures can disappear from our radar. Seychelles. A lonely archipelago of islands. A thousand kilometers from anywhere, huge granite mountains rise from the Indian Ocean. Shrouded in cloud forest, insectivorous plants colonized and endemic species thrived. While in the surrounding seas, dugongs once bred and crocodiles battled with huge primeval sharks. The dugongs and crocodiles have long since disappeared. But one giant shark is still found around these mid-oceanic outcrops. Whale shark aggregate here every year from September to November. Like in Mexico, they're all young adults. However, unlike Mexico, where the population is a mixture of both sexes, these are not only all young, but they're all immature males. And this is a pattern that's been observed in other places where whale shark aggregates. Why? Since the mid-90s, a research project has been based here, trying to unravel some of the mysteries surrounding the whale shark. Maybe tracking where they go when they leave Seychelles waters will provide answers to some of the questions, and perhaps lead to the bigger fish. Dr David Rowat established the research project and has made it his life's work to discover their secrets. The island of Mahe sits on this big, shallow continental plateau, and that tends to generate a lot of plankton. And it's the plankton that attracts the sharks in. So when we've got lots of plankton, the sharks will come in, and then when the plankton tends to disappear, then we tend to lose the sharks. So what we try and do is to track the sharks using various types of tag. The Seychelles team are making the most of every weapon in their armory. Using the microlight, they've been studying the shark for many years, trying to discover where do the shark go when they leave Seychelles. Whale sharks are found in the warmer waters of oceans around the world. With such a wide distribution, aerial spotting is by far the best way to locate the fish. These gentle giants grow to 15 meters long and can weigh up to 12,500 kilos. But despite their great size, finding such a huge fish in the vast expanse of the ocean isn't easy. The pilots can be in the air for several hours every day. When the microlight finds the shark, the pilot radios into the team on the boat. Then the real work begins. Seventy years ago, the region around Papua New Guinea became, for a time, the focus of the Battle of the Pacific. War raged around the planet. Not even the remotest bays and villages escaped the destruction. And wreckage from the conflict can still be found. In shallow waters, this small inshore Japanese coaster has become encrusted with corals and surrounded by fish. A weapon of war, now become an undersea garden, a shelter for the creatures of the reef. Deeper and more mysterious, the eerie wreck of a larger Japanese freighter is virtually intact. Few corals grow at this depth and few fish inhabit the wreck. Part of its cargo still remains. Sake bottles, once destined to keep troop morale high, now litter one of the ship's holds. The wooden cases containing them having long since rotted away. The fathers and grandfathers of local fishermen still tell tales of those days. But today another legend has been born in the region. That of the giants of Chenderawasi Bay. Bagans of fishing pontoons moored several kilometers offshore. It's a new type of fishing in the area. The fishermen coming from the distant island of Sulawesi. The fishermen catch huge quantities of small silver fish, known as puri. Most of this they dry in the sun for sale to local towns and villages. And some they share with the giant visitors that cruise from bagan to bagan in search of a meal. The whale shark have learned that by sucking on the nets, they can extract the smallest of fish. And also the mashed up scraps from the bottom of the nets. Hanging vertically in the water, each mouthful is a nutritious soup. It's an aberration in behavior in these giant sharks that's seen nowhere else. When they tire of maintaining this position, or are pushed out of the way by a competitor, they circle below the bagan before returning for another try. The fishermen have come to regard them not as a nuisance, but as a good omen. I like whale shark because when they're here, they bring lots of fish with them. So we always hope that the whale shark will come. Seeing how keen the shark were to hoover up scraps, the fishermen started feeding them. And an unlikely relationship has grown between these Indonesian fishermen and the giant shark. Day and night, the whale shark patrol the bagans. If the catches pour on one, they move on to another where the fishing is better. While for most people seeing a whale shark is a lifetime dream, here they're just part of the scenery. Time can pass slowly on the bagans. Fishermen can be on board for several days at a time. So the whale shark has become a welcome distraction. I enjoy playing with the whale shark. Sometimes I jump in the water with them. Their skin has a rough texture, but I really like swimming with them. And in this remote region, where folklore and traditions are still more powerful than the written word, legends have grown up around the shark. There is a story in my family. One of my ancestors, a long time ago, was married to a Chinese woman. And they were sailing from Manakwari on their way here. They were caught in a big storm and the boat sank. The whale shark and the dolphin came and helped to bring them back to Kuatasuri. It's a story that's been passed down from generation to generation. Isla Mujeres translates as the island of women. Legend states it was used by the Mayan people as a sanctuary dedicated to their goddess of love and fertility. Others say the name goes back to Spanish buccaneers, who kept their lovers isolated here, while they plundered galleons and pillaged cities on the Mexican mainland. Today, Isla Mujeres is known for other reasons. The arrival of the whale shark marks the start of a tourism frenzy, as visitors from around the world gather to swim with the giant fish. Every morning, the boats head out to locate the shark, which may be 30 kilometers or more off the island, depending on sea conditions and currents. Though the reason for the shark aggregating here is to feed on the snapper eggs, the composition of the gathering is a mystery. All are juveniles and immature adults. So where are the fully grown adults? Why don't they come to join in the feeding frenzy? And where are the very young? Why are they not here? These are questions that science has not yet answered. Whale shark aggregations are not uncommon. There are a number of other hot spots around the ocean, where they gather at specific times of year. And researchers at many of these report similar compositions of juvenile shark with adults significantly absent. The Seychelles research team have made a fascinating discovery. Not only are the shark aggregating around the islands every year all juvenile, but it's also a single sex gathering. The shark are all juvenile males, and this discovery is being reflected at many other whale shark hot spots. In many creatures, the purpose of aggregation is to mate, but clearly this can't be so in the whale shark. But they must mate somewhere, and this can't be left to random chance meetings of mature adults in the vast oceans. So where do they mate? No one has ever witnessed this. And another mystery. The shark give birth to live young of around a metre long. So where are these whale shark pups? And where do the adult females give birth to their live young? In the whole history of research into these giants, less than a dozen pups have ever been found. So where are the adult shark, both male and female? Dr David Rowat hopes that by tracking the shark on their oceanic wanderings, he might find some answers. To do this, he's applying cutting-edge satellite technology. And this is called a pop-up archival tag. It's a pop-up because there is a little wire, magnesium wire in here, that the tag will send an electrical current to on a set date. And that electrical current causes this little wire to melt, and then the tag breaks free, and then the antenna breaks the surface. And once the antenna breaks the surface, the tag will try and transmit the data that it's been storing from the shark. And what data is it? Well, basically three types of data. It's storing information on depth, temperature and light intensity. From this data, scientists can calculate the position and track of the shark. And the research has come up with unexpected and intriguing results. The crew on the Papuan Bagans have no knowledge of the science. Like fishermen everywhere, much of their time is spent waiting. Just a couple of metres below the card game, the whale shark continue their relentless patrol. Intriguingly, as in Seychelles, all these shark are male, and all, despite their often massive size, are still not fully grown. During the day, fishermen pass their time hoping for bigger catches than the night-time puri. Reef fish, like the Papuan Bagans, are not the only fish to be caught. Or perhaps a passing tuna. But their main work takes place during the hours of darkness. Dusk approaches and the fishermen start releasing the net. As the net's dropped, the leftovers spill into the water. A thick soup. It's a moment the shark have been waiting for. There's a sudden feeding frenzy. As the camera and cameraman are thrown about, you remember that these are sharks. Huge creatures, weighing many tons, and in their own environment. As quickly as it started, the frenzy is over. The nets drop to around 10 to 15 metres under the bagan. And as night falls, they power up their banks of lights. Small fish are drawn in by the lights. On a good night's fishing, the crew may haul the net several times. The whale shark also know that the lights attract puri. Huge shadows emerging from the inky black of the night-time sea. Briefly silhouetted by the bagan lights, before disappearing again into the night on their relentless patrolling. The shark know that this night-time concentration of puri, under the lights of the bagan, is the easiest of meals. The fishermen do all the work, and the shark just take their pickings. Though the fishermen regard the sharks as a lucky omen, they can sometimes be a problem. I like the whale shark, because when they're here, it means they bring lots of fish around the bagan. But sometimes they bring bad luck, because during the night, when we lower the net, the whale shark is also under the bagan. So we cannot lift up the nets. The haul at daybreak shows that puri are not the only catch of the night. In fact, there's a larger and a far more valuable fish in the net. Photographer and environmental campaigner Michael Orr was one of the first to document the whale shark in Chenderawasi Bay, and has become one of the most passionate advocates for protection of the sharks. He's genuinely worried that this accidental bycatch of the shark could lead to the extermination of this unique population. A whale shark fin is the most prized fin in the world, especially in China, the Chinese and Hong Kong market. Because unlike any other sharks, only half or quarter of the fin can be used. A whale shark fin is tender and soft. They can use the entire fin, the entire dorsal fin, the entire pectoral fin. It's so large, the pectoral fin and the tail. To give you an idea of the dorsal fin alone in Hong Kong, at trade price, a dorsal fin is worth between $1,005 to $3,005 US dollars. For one fin, that's lots of money. So for someone, for them to sell, to harvest a whale shark, each of the fin, you're talking about $1,000 at least to sell it off. So it's very valuable, especially they can feed the entire village with one whale shark. And that's very real. The research in seychelles into where the shark go when they leave the islands has posed more questions than provided explanations. Data from tagged sharks shows unexpected results. So this is the first one. And this shark was tagged here in the Seychelles. And you can see it left the Seychelles plateau quite quickly and was in deep water. And then it moved across to the top of the Mozambique Channel before going due north and carrying on towards the coast of Somalia. And this was our second one. And he pretty much did the same as the first. Again, came to the south of the Seychelles plateau, hung around the edge of the drop-off, and then started to move across towards the east coast of Africa. But the third shark, tagged on the same day as the second, just a couple of hundred metres away, did exactly the opposite. He went to the north of the Seychelles plateau. And then we didn't hear anything from the tag for seven weeks. And then we got the first signal here. And then, in fact, we started to build up a whole chain of signals from here down to here. And that's where the tag detached. It was due south of Sri Lanka, just south of the equator. So that was some 3,600 kilometres away. So when they leave Seychelles, they starburst inexplicably. What might have been expected as a migration route, being followed by the shark tracking food, turns out to be far from that. Another mystery in the lives of these ocean giants. Over 30 kilometres off Isla Mujeres, the surface of the ocean is bubbling with sharks. Below the surface, visibility is reduced by the density of the snapper spawn. Sharks are on a feeding mission and seem oblivious to the humans in their path. There are layers of shark wherever the camera's pointed. Research off Isla Mujeres has shown shark hair disperses widely, and apparently as randomly, as in Seychelles. Some scatter through the Gulf of Mexico. Some head to the Florida Straits. And still others travel even further. A tagged pregnant eight metre long female travelled nearly 8,000 kilometres over 150 days. From the Yucatan Peninsula, through the Caribbean Sea, to south of the equator. Ending up roughly halfway between Brazil and Africa. No one's certain where whale sharks breed or give birth. But as a result of the information provided by this tag, researchers believe that this area may be one of their elusive pupping grounds. Other information from tagging has provided new pieces in the jigsaw of the whale shark's life. One tagged shark dived 1,500 metres, a kilometre and a half. And another tag has recorded a dive to almost two kilometres. Despite many theories, that they do this to rest, to cool off, to get rid of parasites, scientists actually don't really know why the animals go so deep. In Chendrawassi Bay, after a long night's work, the Papuan fishermen have to deal with the problem of a whale shark in the net. It's a catch that could be worth thousands of dollars on the Asian markets. A fortune to men whose income is just a few dollars a week. But despite the value of the catch, their priority is not to butcher the shark, but to free it before damage is caused to the net. Not an easy job when several tons of fish is thrashing around. I wish I could talk to the whale shark and say, please, can you go away at night and then come back during the day and then we will feed you during the day and don't disturb us during the night when we are fishing. This shark is incredibly fortunate. The fishermen let it go free. Michael Orr is pessimistic as to how long this will continue. So why do they release such a potentially valuable catch? The whale sharks bring in the puri, the bait fish, and sort of co-exist in a sense that when they see a whale shark, they have a better catch of bait fish. And also I think that there's no demand has yet come to this part of the world, very remote part of the world, for whale sharks, for fins. So there's no reason for them to harvest the shark because there's no demand. Nobody come here and ask them to harvest the fins. But it will change. I think it will change because as the world knows about this location now, you just take the traders to move in here and offer them money for the fins and why not? It's a depressing thought because these shark of Chendrawasih Bay gives a unique chance to study their lives. Little research has been carried out to date. In this remote region of Papua, the behaviour was only discovered a few years ago. But initial tagging results suggest that the shark do leave the bay, travelling up to a thousand kilometres away. And then they return. Almost half of those photographed on Michael's annual expeditions are being identified as shark that were there in previous years. It's a happy sign because we're seeing the same animal again and again in the same area. Which raises the question, how do they know to return to the Bagans, which move from place to place wherever the fishing's best? How do whale shark travel thousands of kilometres away and then locate a small man-made structure in a huge ocean? The whale shark's brain clearly holds mysteries we do not yet understand. A similar question has been taxing Dr David Roat and his Seychelles team. Are they seeing different shark every year or are the same shark returning? Indeed, how do you tell if it's the same shark? One of the earliest methods was to attach a tag to the shark. So if it's seen again, the number clearly identifies it. Like a number plate on a car. Attaching tags is hit and miss. A far easier and more effective method has evolved. Photo identification. Scientists have discovered that the area behind the fifth gill slit, which is just here, is unique to every individual shark and both the left and the right side are different. So just like our fingerprints, the sharks have different patterns on both of their sides. So all you need to do is click on the spots to plot them for the animal. So now that you've created a fingerprint, you can now search within the database, which we have hundreds and hundreds of photos in, to see if it matches anyone we've seen in the Seychelles before or whether they're new to us this year. So once we click search, it will come up with our search results. So I'll double click on our first result and it comes up with a comparison window. I can tell you this is the same shark. Key things I would look for are these lines that run along here, right at the bottom of its fifth gill slit and also the circles that sit around our spots here. You can see that they match on both of the pictures. And this shark is just one of many returning. Around half the whale shark encountered in any one year in Seychelles. Have been observed here in previous years. So though they scatter in seemingly random directions, something draws these juvenile male shark back from all corners of the ocean. Satellite tags show us where the shark have gone. Photo identification tells us if the same shark are returning year after year. Now scientists have a new tool to build a picture of the day-to-day life of the shark. These are the new generation of behavioral tags. It's called a DD or a daily diary. And the tag does all of the normal things that a PAT tag does. But in addition, it has sensors that tell it in which direction it's facing and at what angle tag is, whether it's tilted, inclined. And up in the top here, if I can take this out, there is a little impeller that spins around and it gives the flow how fast through the water that this is being moved. And it's based upon a system that was used from the very earliest days of flying, which is called dead reckoning. Using the information from these tags, both in terms of how fast it's been going and what direction it was heading, we can then build up a three-dimensional plot of what this animal was doing. Although Isla Mujeres has been a popular tourist destination for many years, the island's whale shark ecotourism has only recently exploded. The local government have restricted tourists to snorkeling only, no scuba diving is allowed. All boat owners must have a permit. And there are other regulations, such as no touching the shark, no flash photography and only the use of biodegradable sunblock. But despite the best of intentions, with around 100 licensed boats, plus unlicensed operators, the reality is chaos. There can be hundreds of people in the water at any one time. In strong currents and choppy seas, with boats everywhere, the skipper's priority is trying to keep an eye on their own snorkelers in the water. And the sharks seem oblivious to the danger. With dozens of propellers churning the water, it's hard to find a shark that hasn't been cut up in some way by a boat. The majority have got clear stripes from a propeller across their back. Others have had their dorsal fins sliced. Lots are missing chunks of tail. It's rare to see a shark with all its fins intact. How long can this frenzied level of tourism be sustained? Scientists fear that the long-term effects may ultimately drive the shark from these seasonal feeding grounds. In many regions, whale shark are still targeted by fisheries as a valuable prize, particularly in Southeast Asia. Even if some countries introduce conservation measures, with these giant fish migrating such massive distances, it's little help if they're only protected in certain parts of their ocean wanderings, only to be slaughtered elsewhere. And those in Chendrawasi Bay are in very real danger. Protection's fragile. No pack of creatures could be more vulnerable. Conditioned to remaining around the Bagans, they could be targeted at any time by commercial shark finning. Innocent trust in humans could result in a harpoon. And the cruel sawing off of the fins while the shark still struggled. In a morning's fishing, the giants of Chendrawasi Bay could be no more. Our planet's greatest fish is extremely vulnerable. Fisheries targeting them have collapsed as populations of the shark have simply disappeared. Research is essential to ensure that these ocean giants don't simply fade into extinction. Scientists' results are producing more questions than answers. Where they mate and give birth, and where the pups live, still remain mysteries. And only if the roots of their oceanic journeys are known and understood, can conservation measures be put in place. The answers to so many questions are still elusive. The world's largest shark still remains an enigma. Maybe the unique bond between the shark and the fishermen of Chendrawasi Bay will provide the key to unlock the global whale shark mystery.