The World Of Spinner Dolphins
The following is the final narration script for our film Ocean Acrobats: The World of the Spinner Dolphin. It has lots of information about spinners in Hawaii and Tahiti and the problems spinners still face from the tuna Fishery.
In the tropical oceans of the world lives a species of dolphin unlike any other. . . small... energetic. . . intensely athletic. . . Herman Melville called them the "lads that always live before the wind" ... who swim "in hilarious shoals, which keep tossing themselves to heaven like caps in a fourth-of-july crowd. . . "
Today we know them as spinner dolphins. And they are among the best-studied marine mammals on earth. . . . . . studies that are now revealing just how it is that spinner dolphins face the challenges of the sea -- with their own unique brand of invention, energy, and joy.
Narration script, 1.7.98
Although many spinner dolphins live their entire lives in the deep water far offshore, some schools seek shelter near volcanic islands. This morning, off the big island of hawaii. . . a group of spinners heads into shore. All night they've hunted in the abyss. Now, well-fed, they're ready to rest inside the protective arms of the land. They arrive at the island energized and in high spirits. Only slowly will the excitement of the night wear off enough for them to sleep.
Of approximately 80 species of whales and dolphins worldwide, spinners are the most accomplished aerialists of all. Many other dolphins -- like this rough-tooth dolphin -- leap. . . and the great whales breach... but only the spinners spin-- --up to seven-and-a-half revolutions in the 1.25 seconds they're in the air. Spinning is the defining art of this species.
Even infant dolphins practice the rudiments of spinning. . . almost from the moment of birth. . . Only now, are scientists beginning to decipher the mysterious language of spinning. But with each answer come new questions. How does spinning enable the school as a whole to function as a cooperative society of friends? And how does this help the dolphins to survive?
This morning -- with the winds out of the northeast -- the spinners head to the lee side of the big island of hawaii. The windward side is far too turbulent for them to rest in safety. But on the southwestern shore, in a protected bay called Ke-ah-lah-kekua, they find the ideal conditions for their midday sleep. A calm surface and clear water have attracted 100 dolphins to Ke-ah-lah-kekua this morning.
The spinners have chosen this bay because of its sandy bottom -- against which they can visually detect the approach of a predator. Sharks are a major concern -- and a serious threat to dolphins of all kinds. Many smaller cetaceans -- like this spotted dolphin -- bear the scars of shark bites they survived... in this case, a missing front flipper.
But most such encounters -- such as this with a dolphin recently attacked by a shark -- are surely fatal. Against a sandy bottom, dolphins can see sharks and drive them away. This morning, as the dolphins arrive at Ke-ah-lah-kekua Bay, there are no sharks to be seen.
Slowly, the school winds down from its energetic behavior of the night. Over the next two hours -- as the dolphins enter into what scientists refer to as the "restless" state -- the school tightens up, synchronizes its breathing, and begins to prepare for sleep. The subgroups of the school move closer together. Coalitions of adult and sub-adult males move alongside groups of females and small calves.
Males are distinguished from females by the keels under their tailstocks . . . and by the triangular-shaped dorsal fins on their backs. Juvenile dolphins within the school continue to play. . . but only within the borders of the "playpen" -- an area contained by the larger group. Much affectionate touching and rubbing occurs at this time. . . some dolphins engage in games of patty-cakes. . . one swimming underneath another while scissoring their pectoral fins back and forth. Others "hold hands. . . " Some caress each other with their tail flukes. . .
Receptive females are accompanied by small groups of males who take turns mating with them. . . Periodically the members of the school come together in group caressing bouts. As numerous dolphins twist and turn together, their flashing white bellies attract even more individuals into the swarm. These displays of mass affection may serve to bond the members of the school tightly together.
Spinner schools are believed to be made up of a society of friends... individuals not necessarily related by blood, but instead drawn closely together for mutual aid in defense and hunting. One remarkable aspect of their defensive strategy has been observed by Suchi Sa-ra-kuss, Field Research Manager for the conservation organization Earthtrust
One morning I went out and I saw a group of 30 animals. And it appeared that they were predominantly male. They were lined up side-to-side, diving and surfacing synchronously. Furthermore, they were swimming quite slowly. And all of a sudden, it was like someone had said "on your mark, get set, go," you could see they erupted into a frenzy of activity.
Suddenly the dolphins split into two groups, and began to skirmish. . . . Operating in perfect synchrony, each group tried to break-up the tight formation of the other...
And then just as suddenly it stopped, and they went back into this what I call a drill formation. Psarakos: While the dolphins were swimming slowly there was no sound, it was completely silent. . . When they went into these frenzied outbursts there was a lot of squawking, and whistling and clicking and just a huge frenzy of sound that would stop, just as quickly.
Time and again, the two groups played out their scrimmage. . . The defending team frequently swimming upside down above the attacking team. . . The same posture they would use to defend themselves against predators.
I had the distinct impression as i followed along that i was watching some sort of drill practice. Perhaps in this case it's something like a shark srill. Perhaps in this case it's something like a shark drill. Perhaps these are males who are usually in protector positions, and they need to practice to make sure that they can at a moment's notice protect the rest of the pod.
A hundred miles from ke ah luh kekua bay, the rugged, southern shore of the island of lanai also provides sandy bays where the spinners can rest. By midday, the dolphins at Manele Bay are deep in sleep. Grouped together in tight formations, they sink to the sandy bottom, where they remain submerged for four to five minutes at a time.
This period of rest does not resemble sleep as we know it. The dolphins are not actually unconscious -- as only parts of their brains are asleep at any one time. Most striking now is their silence.
There you can hear these click-whistles. And these whistles have been studied. . .
Dr. Ken Marten, director of research for earthtrust, studies the vocalizations of spinner dolphins. His office is alongside the bottlenose dolphin pool at sea life park, near honolulu. Marten analyzes the sound from videotapes of wild spinner dolphins.
...that's one of the whistles there. . . . Now there's a nice whistle. . . So what the scientist does it look at the course of the whistle through time. time is this way, on the x-axis. On the y-axis is frequency. And on the z-axis, in other words, intensity, the whiteness shows the intensity of the sound at that frequency.
Actually most of the sounds that we get from them are pulse sounds -- "nyyea, nyyea" -- things like that. And of course the pulse sounds go right up into the ultrasonic range. The pulse sounds are very difficult to study in that functionally they are a mixture of echolocation and communication. And who knows, maybe sometimes they serve both functions at once.
Echolocation sounds enable dolphins to track objects in dim or dark water... to in effect "see" much further than their eyes alone will allow. Their complex array of whistle sounds are the way that dolphins talk to one another. . . The spinners can even identify themselves with sounds they make while trailing bubbles from their blowholes -- sounds called signature whistles.
This afternoon at lanai, the spinners have turned their sound systems off -- allowing critically important areas of their brains to sleep. Now, without sound, they rely heavily on sight. And this is why clear water and white-sand bays are so important to them. During the period of rest, they must group tightly together, combining their eyes into a super-organ upon which they all rely.
For the next several hours, the dolphins maintain this semi-conscious patrol. . . rising and falling in tandem. . . drifting ghost-like through the shallows.
. . . animals at 8 o'clock. . .
On the other side of the equator, Dr. Michael Poole has been studying the spinner dolphins of french polynesia for more than ten years.
Poole: ...vertical spin falling horizontal, 12 o'clock...
Like the hawaiian spinners, these tahitian dolphins also use volcanic islands as daytime resting sites. The french polynesian island of moorea is surrounded by a barrier reef. Inside the reef is a shallow, turquoise-blue lagoon -- completely sheltered from the mid-ocean waves that pound the outer reef. Twelve passes through the reef allow the flow of water between the lagoon and the open sea. Spinner dolphins use these passes as doorways into the lagoon.
Poole: Activity at 1 o'clock. . . Forward slapping at 2 o'clock also, much closer. Forward slapping again, 2 o'clock. Forward slapping again. Side slap. Side Slap.
Michael Poole has extensively documented the dolphins' use of the passes at Moorea. Although on any given day the spinners have a dozen passes through which to enter the lagoon, prevailing weather will generally reduce this number to only three or four.
Poole: This is one of the three bays that the dolphins use here on the east coast. It's also one of the bays from which they've been displaced, or at least been displaced to certain regions of the bay. Poole has discovered that some of the critical resting sites for the spinners are now limited by a variety of manmade causes.
Poole: The animals have been moved from some areas into others because of the amount of boat traffic and jet ski traffic that we have here. There's been an incredible increase in the past 5-7 years in the numbers of jet skis. Because they're going so fast they often don't see the dolphin school ahead of them and end up going right over it.
Today, ferries, speedboats and jet skis frequently drive the dolphins from the passes into the more shallow -- and less favored -- water further inside the bays. But these upper bays are also impacted -- this time by human activities on the land. . .
Pineapples have become a major commodity in french polynesia. Yet many of these plantations have been poorly laid out. With each rain, tons of topsoil wash from the slopes and into the same white-sand bays where the dolphins come to rest.
Unfortunately due to the increased erosion due to agricultural practices, primarily pineapple plantations, we're getting the white-sand bottoms of these areas covered with terrestrial sediments. The animals prefer to rest over white sand areas, so they're now leaving areas, being forced out of areas because of this increased erosion.
Besieged on all sides, these spinner dolphins may one day find themselves without any haven at all on the island of moorea. But this afternoon, as the sun begins to drop, the dolphins slowly awaken from rest. From the surface, the first sign is an increase of aerial displays.
Scientists studying spinner dolphins have catalogued seven types of aerial behaviors. Simplest of all are the nose outs . . .as the beak is thrust from the surface. . . this is often one of the first signs of a school coming out of the rest period. The spinners use tail slaps as acoustic signals-- giving cues about danger. . . or a signal to dive. They can also be performed upside-down. Head slaps . . . side slaps. . . and back slaps are most frequently seen as the school begins to pick up speed. . . Spinner dolphins also perform a series of leaps, including arcuate leaps. . .salmon leaps. . .and tail-over-head leaps. . .
Last -- and most spectacular -- are the spins themselves. Many animals spin repeatedly. . . with each spin tending to get smaller and Smaller . . finally finishing up with an emphatic side slap.
The power of the spin comes from the tremendous acceleration under the water. . . And the torque of the tail as the dolphin breaks the surface. The aftermath of the spin -- the sound of the slap. . . the splash on the surface . . . and the dense bubble cloud underwater, which even distant dolphins can pick up through their echolocation. . . may be the real purpose of the spin.
Spinner dolphins maximize the effect of this splash by twisting around to land in a belly-flop, or back-flop. Spins are most frequently performed while the school is spread out across the water. A spinning dolphin may be signaling to the others: "here I am. . . . here is where I am going. . . " The effect of many dolphins spinning and leaping at once, defines what scientists call the envelope of the school -- that is, its size, direction, and speed of travel.
This afternoon in moorea, as the spinners awaken from their afternoon rest, some members begin to spin, urging the school to move out of the lagoon. . . . But other members are reluctant to leave just yet, and slowly nudge the school back into the bay, and into resting behavior. For the next hour or more, the spinners perform this zig-zag pattern. . . going airborne, moving out. . . . then quieting down, and drifting back toward shore...
Because there is no hierarchy in spinner society, movement and change are decided by group consensus. Only when all the members of the school are ready to make the move into the open sea will the charge begin. . . . Suddenly, the vocalizations of the school burst forth. . . . The sound is a cacophony of squawks, blats, barks, whistles, and clicks -- as all the members of the school literally shout at once.
For the dolphins, this uniquely noisy display now signals that they are indeed ready to move into the open sea. But to clear the lagoon, they must exit through one of the passes. The spinners will not travel through the surf itself, as the crashing waves create a barrier of bubbles which their sonar cannot penetrate.
Dr. Michael Poole recalls the day when the weather changed suddenly, the waves building so high that they closed out the dolphins' only exit.
Poole: The waves were so much larger even than they are today, that the entire pass was closing out. We stayed inshore and on my boat -- we had two teams working simultaneously -- watching these dolphins the entire day. At sunset, around 6:00 or 6:15, the animals were still here.
Never before had the dolphins stayed inside the lagoon until sunset . . . but with several newborn calves and enormous waves blocking their route, the school could not leave. . . The dolphins were hungry -- especially the females with young. As night fell, the waves grew even larger.
Finally, nearly 30 hours after entering the lagoon, the dolphins' doorway opened once again.
Poole: As the swell dropped back down they then went out into the open ocean and left. I believe that they'd been stuck here through that night and through that day because they'd been unable to go out with their small calves. But this afternoon, the pass is wide open, and the dolphins swim through easily on their way out to the open sea.
Once outside the reef, conditions change immediately. Ocean swells build all around. The school picks up speed. . . Spreading out across the water. . . signaling to each other through aerial displays. . . As the spinners turn the northwest corner of moorea, their keen hearing picks up powerfully resonant sounds. . . ..
The songs of humpbacks are punctuated by their own brand of aerial behavior. . . Two 50-ton males slash their tails and breach. . . They are competing for a female, who tries to elude them.
A pod of pilot whales join the pursuit. As does a school of rizzo's dolphins -- all seemingly drawn by curiosity to the mating of the giants. Dolphins and pilot whales dive across the bows of the great whales. . . surfing them as they would a ship. The humpbacks seem oblivious to the smaller cetaceans. . . absorbed, as they are, in their own graceful and powerful ritual. . . as one male struggles to shoulder aside the other, in pursuit of the female.
But this spectacle -- however compelling -- does not divert the spinner dolphins from their agenda, as they head out to sea. Spinners rarely deviate from their daily schedule, no matter what goes on around them. Interactions between different species of whales and dolphins are rarely observed in the wild, let alone understood. But one of the most intriguing cases of a relationship between species can be found 300 miles north of moorea, on a coral atoll known as rangiroa.
Millions of years ago, rangiroa was also a massive island. Today its volcanoes are long extinct, eroded and subsided entirely back into the sea. Only two passes remain into rangiroa's lagoon. . . and with each change of the tides, huge flows of water rip through the passes. . . sweeping nutrients in and out, a fluid pendulum of the sea. These passes have become a gathering place for an astonishing variety of marine life. . . . Including hundreds -- perhaps thousands -- of sharks. . .
Because of the sharks, and the rip tides, the spinner dolphins of rangiroa never enter this lagoon. . . Instead, resting offshore each afternoon. But a school of bottlenose dolphins -- much larger and stronger than the spinners -- have chosen to live in these passes year-round. And twice a day, when the tides change, the 10-foot high standing waves of the rip tide become the bottlenose dolphin's playground. . . ..
For human swimmers, the whirlpools and undertows created by this rip tide would prove fatal... Dragging them hundreds of feet deep and sweeping them far out to sea. But for the dolphins, these challenging conditions are nothing short of exhilarating.
Year after year, the bottlenose of rangiroa have enjoyed this twice-daily recreation, passing the surfing art on from one generation to the next. But several years ago, observers here noticed something new. . . . a dolphin acting quite differently in the waves than the others. . . . .a much smaller dolphin. . . spinning. At that time, for reasons we can only guess, this pod of bottlenose dolphins adopted an infant spinner dolphin.
With their short rounded beaks, the bottlenose are twice the length and ten times the weight of the spinner. Yet despite these differences, the young spinner has lived among these bottlenose. . . doing everything just as the larger dolphins do. . . including entering the standing waves twice a day. But when the bottlenose leap, the spinner spins. . . .
In addition to surfing the pass, these dolphins have another kind of thrill to look forward to. . . . Once a week a cruise ship visits Rangiroa. Expertly using the pressure wave off the bow, the dolphins get the effortless ride of a lifetime. . . surfing sideways and even upside-down in the flow. . .
At day's end, as the bottlenose and their adopted spinner surf the waves, a large school of spinner dolphins further offshore makes haste for their feeding grounds. . . Now all the collective energy of the school comes together as the dolphins approach the most thrilling and dangerous part of their lives.
Scientists have likened the dash to the deep -- and all its accompanying aerial displays -- as akin to a football team psyching itself before a game. This communal pep rally serves yet again to synchronize the dolphins' intentions, and perhaps to overcome their fears. For as night falls, a change takes place in the deep water far below.
A community of marine life, known as the deep scattering layer -- which spends the daylight hours at depths of up to 3,000 feet Ñ now begins to migrate upward. As these riches come within reach, many surface dwellers -- including the spinner dolphins -- begin to hunt. Small subgroups spread out across the sea.
Despite being separated by several miles of water, the school still coordinates its activities through sound -- -and through spinning -- which reaches an explosive crescendo in the darkness of night . . . Time after time, the dolphins dive . . . down into the utter darkness at 800 feet, or more.
Schools of squid rise with the deep scattering layer. Jet-propelled, they are among the most elusive of prey.
Yet dolphins of many kinds are adept at catching them. For all the spinners' skill and agility in this eerie world, they are wary of predators. Many sharks live in the deep scattering layer . . .
Using their echolocation, the spinners scan the darkness. . . then using their whistles, they call members of the school back together. and unite for their defense . . . And so most nights, the collective defenses of the dolphin school protect each member from harm. By dawn, the spinners regroup. Well-fed, they move once again towards the shelter of the islands.
Millions of years of natural selection have made spinner dolphins supremely adapted to the paradoxical worlds they inhabit . . one in the darkness of the abyss . . the other in the sunlit shallows. But nothing in their evolutionary past has prepared these dolphins for the onslaughts of the modern age. In the open sea, spinner dolphins and spotted dolphins frequently swim above large schools of yellowfin tuna. Fishermen in the eastern tropical pacific use dolphins to locate the tuna. . . Then set their nets around the dolphins.
Setting nets on dolphins to catch tuna kills them in large numbers. There's no way to avoid that. And really what the public ought to understand is that the problem is not solved. Dr. Ken Marten was an official observer aboard u.s. tuna boats for two years. His job was to count and report the number of dolphins killed.
The mother boat launches 4 to 6 speedboats which chase the dolphins for an hour or more at high speed until the dolphins are exhausted. The mother boat approaches and sets the long purse seine net around the dolphins.
Any place the net is still open, the speedboats are sent and now they have a new function -- to drop bombs into the water, that explode, and prevent the dolphins from escaping out of the net. And the rationale behind that is that if the dolphins ever escape out of the net, the tuna escape with them.
The nature of such a huge net around dolphins for such a long period of time, is that dolphins can get caught in folds of the net and drown. And it can happen to all of the dolphins in the net. And the number of dolphins in the net may be 3 or 4,000. These aggregations of spinner and spotted dolphins in the deep eastern tropical pacific are almost like little cities of dolphins. And the entire city can be wiped out.
The spinners' brilliant defensive systems. . . group loyalty . . . sonar . . . speed and agility . . offer them no protection here -- and may even work against their survival in the chaos of the nets.
Many of the dolphins who do escape may die soon afterward . . . as they are now completely deafened by the bomb explosions underwater. Tragically for a dolphin being deaf is equivalent to being blind.
I can state this on my own experience, because when the tuna fishermen used to throw the bombs at me, as an observer, to keep me from reporting large kills, those bombs made me deaf for about a day. Nor do the "dolphin-safe" labels appearing on some cans of tuna offer absolute guarantees that no dolphins were killed . . . Meanwhile, the effect of tuna fishing on dolphins has been catastrophic. Today, more than 60 percent of the population of spinner dolphins in the Eastern tropical pacific has been wiped out in the tuna nets.
This morning, after a successful night of hunting, the spinner dolphins of Kealakekua Bay are returning to shore. Mornings are a time of celebration -- as the members of the school meet, and play together. Youngsters practice their lessons. Little by little, the warm, clear waters entice them to rest . . . the dolphins draw closer. Together they rise and fall from the surface . . . until each spinner slips into sleep, safe inside a cocoon of friends.
In the 30 years that spinner dolphins have been studied, much has been Deciphered of their lives in the wild. Yet most of their world remains -- and may always remain -- completely mysterious. They thrive in what is essentially a different universe . . and yet, we feel close to them.
Perhaps the attraction lies in a sense of kindred spirit . . .
For although we understand something now of the complex and serious business of their lives. . . . we can also feel their unique and joyful energy. . . . . that moment of flight . . . that instant when the burdens of life are cast away.