A fin and a prayer
With their large brains, considerable capacity to learn, and propensity for interacting with humans, dolphins are undoubtedly among the most intelligent—and fascinating— of animals. Yet, given their nomadic lives in the ocean, they are difficult subjects to get to know. The bottlenose dolphins of Fiordland’s Doubtful Sound, however, are a resident population, much studied by biologists from the University of Otago, who are starting to piece together the outlines of their mysterious lives.
Long before sunrise, the alarm wakes us and we stumble into the shadow land of a Doubtful Sound morning. Mystery hangs in the air. Not the mystery of something unusual or awry, but of something awaiting discovery. At the water’s edge in Deep Cove the murmur of distant voices and the hum of a generator are the only human sounds. Old wooden fishing boats painted in red, blue and white float immobile atop their perfect reflections. A light mist winds its way through the forest and rolls silently on to the fiord, adding a chill to the air and clearing drowsiness from the mind.
The heavy mooring rope slaps the water as we haul Wilma Jane, our research runabout, into the beach. After bailing bilge and rainwater, we start the engine and speed off into the oily blackness of the sea.
Our search for dolphins starts in Hall Arm, the innermost of Doubtful Sound’s many limbs. All eyes search for small patches of white water and puffs of spray. In Crooked Arm a thick bank of fog turns us back, past the shores of Secretary Island and into the mouth of Bradshaw and Thompson Sounds.
Before arriving here, I had asked David Lusseau, the University of Otago marine biologist who is my host, how long it normally took to find the dolphins, and how close I could expect to get.
“We will find them quickly,” Lusseau had replied. “The dolphins come very close to the boat. Sometimes they compete with each other to see who gets the best place on Wilma Jane’s bow. We spend several hours a day with them, and you will see many different things.”
We have been an hour and a half on the water, and have yet to see a dolphin.”In other pods I have worked with,” says Lusseau, “you can spend all day looking for the dolphins, and still not find them. This is very unusual for Doubtful Sound.”At 9:30 a voice crackles over the VHF radio. “Wilma Jane, this is Commander Peak. Do you copy, David?” Commander Peak is Fiordland Travel’s main tourist boat operating on Doubtful Sound. Lusseau responds in his rich French accent.
“Commander Peak, this is Wilma Jane, go ahead.”
“G’day, David. Any luck this morning?”
“No sign yet, Frank. Crooked Arm is really foggy. We couldn’t see anything, so we turned around. We are on our way up Bradshaw.””We saw a small pod at Elizabeth Island. Probably a nursery group.”
“Thanks. We’ll go and check them out.”Twenty minutes later, Lusseau points to a dark stretch of shore on the western side of Elizabeth Island.
“There. Do you see them?”
Initially I see nothing, but then I pick up a small break in the calm surface. When we get closer I see a boiling rush of air bubbling to the surface. A dolphin breaks the surface, empties her lungs in a cloud of spray, sucks in a gasp of fresh air, then re-submerges.
“When they make a lot of turbulence like this,” explains Lusseau, ” they have been on a deep dive—probably feeding. That explains why we missed them earlier. In the fiords, bottlenose dolphins have been timed spending up to seven minutes on a dive—some of the longest dives recorded anywhere. These ones are calves and juveniles. They are not as strong as the adults, and they return to the surface before the older females.”
Over the next minute all of the nursery pod returns to the surface. Each dolphin follows the same pattern of bursting through the bubbles, clearing their breathing hole and grabbing a lung-full of air. Many swim up to the boat, as if to say their good mornings to Lusseau. They seem totally relaxed about our presence. After a short recovery period of three to four minutes on the surface, they regroup and dive again. “When they are going on a deep dive they always arch their backs,” Lusseau comments. I watch as one lifts its head out of the water, breathes in, doubles over, forces its head down, lifts its tail and makes a near-vertical descent.
Charts show the depth here as close to 300 m. Little is known about the types of fish that live in the sound, but it is thought they live along shallow ledges or right down on the bottom. “In Milford Sound I saw a dolphin bring a hagfish to the surface. Hagfish are bottom feeders, and the water was 400 m deep—as deep as a bottlenose dolphin has been known to dive,” says Lusseau.
We spend a couple of hours with the nursery pod, observing and recording the typical daily activities: travelling, diving and feeding. Then their behaviour changes. The group spreads out and we see much less diving and a lot of milling around. This is thought to be the time they sleep. Dolphin breathing is not under autonomic control, as it needs to be synchronised with surfacing. For this reason dolphins cannot sleep for extended periods. There are two theories about how they solve this problem. A Russian research group has proposed that they “close down” one hemisphere of their brain at a time, leaving the other to control essential activities, such as breathing. Other researchers believe that dolphins just take micro-naps, during which their brain activity resembles ours when we are in REM sleep.
Lusseau pulls back and gives the group a little peace and quiet. Later in the day we find another pod in Crooked Ann. A young female swims under the boat and performs a few underwater fly-bys, then begins bow-riding. Swimming on her side, she looks me straight in the eye, but I hold her interest only momentarily. With a flick of her tail and a fine adjustment to her pectoral fin she rights herself, breaks the surface, clears her blowhole and soaks me with a fine spray. She fills her lungs, then dives back onto the bow wave. Laughing, Lusseau introduces me to this dolphin. “This is Siren. She was born while Karsten was studying here. She has been brought up with Wilma Jane, and often comes to play with the boat.” With this comment comes a thud of affirmation as Siren crashes into the hull.
Karsten Schneider was the first biologist to study systematically the Doubtful Sound dolphins. He started his work in 1994, soon after it was discovered that the dolphins were permanent residents who apparently never ventured into the turbulent seas outside. This unusual state of affairs meant it was possible to find and observe the same dolphins on a daily basis. Schneider was able to follow the same individuals for several hours a day and habituate them to the presence of the boat. He spent 353 days over three years observing the dolphins, and in this time was able to construct a detailed model of their society. Never before had this sort of work been possible; it had always been deemed impractical to observe the same dolphins on a day-to-day basis. In the early 1970s, Jane Goodall used a very similar technique—following habituated chimpanzees—to revolutionise the study of primates.
On my third day in Doubtful Sound the overnight drizzle turns into steady rain. The sounds of water are everywhere: the boom of water being jettisoned over a cliff, the slap of wavelets against the gunwales of Wilma Jane, the peaceful patter of a million raindrops on the sea surface. During such quiet times I can see how accustomed the dolphins have become to the boat, and how little heed they give us. Schneider, who now works with Natural History New Zealand, the Dunedin documentary film company, says it took a long time to build up this level of acceptance on the part of the dolphins. “My method of observation involved spending up to 10 hours a day with the dolphins,” he says. “I tried to minimise my impact by developing a code of practice. If I was following a group of dolphins and they began changing direction away from the boat, or if individuals performed tail-slaps in front of the boat, I interpreted this as a sign of disturbance and would back off. After an hour I would make another approach. Often their mood had changed and my presence was accepted. If this was not the case, I would pull back again or move on to another group.
“When I was less than 50 m from the dolphins, the boat was kept at idling speed or just fast enough to maintain distance on a parallel course. If I decided to speed up I would signal this by pressing the trim/tilt switch on the outboard motor, to give the dolphins an acoustic warning to stay clear of the propeller. This signaling was soon recognised by the dolphins and obviously understood, because it often led to individuals approaching the bow of the boat in anticipation of bow-riding.”
After a few hours, the dolphins we are following indicate their frustration by repeatedly changing direction away from the boat. Adhering to Schneider’s code of conduct, Lusseau pulls back and decides to look for another group.
We spend a frustrating three hours zig-zagging the outer reaches of Doubtful Sound, catching sight of the dolphins then losing them again amid the chop that often comes up in the afternoons. Despite the difficulties, we stay with the dolphins for most of the afternoon and are rewarded with the very rare sight of a dolphin with a fish in its mouth. This is only the second time Lusseau has seen a Doubtful dolphin with a fish, but we are unable to identify the species.
Very little is known about the diet of the Doubtful Sound dolphins. Schneider explains why: “While bottlenose dolphins frequently feed at the surface in other habitats, we have not seen this in almost a decade of research in Doubtful Sound. Feeding at depth is much more difficult to observe. We think they are non-specialist feeders, and we have anecdotal evidence to support this. Several times I came across fish lost or left by a dolphin. There was a wide variety, including spotties, rattail, hold and a perch.”
When feeding, a group of dolphins will usually dive together, which suggests that they may be hunting cooperatively. There is an unproved theory that dolphins use reflected sound to build up a three-dimensional picture of their prey. Lusseau explains: “Dolphins eavesdrop on the echolocation sounds of other dolphins to interpret what is around. For example, you may have one dolphin echolocating on a fish or a rock wall, and the sound is going to be reflecting off that object. Most of the signal will return to the original dolphin, but you will also get some scattering. A neighbouring dolphin can use this sound to ‘see’ what is there without having to echolocate. The idea is that if one dolphin echolocates from one direction and another dolphin does it from another angle then they get a much better picture of the prey.”
The Doubtful Sound population is thought to be the world’s southernmost resident pod of bottlenose dolphins. Although most bottlenoses are found in warmer, shallower, more open waters, they seem to be highly adaptable, and occur as far north as the Moray of Firth in Scotland and as far south as Stewart Island. Warm-blooded animals living in cold water tend to be big and rotund (so minimising surface area with respect to volume), and this is true of the bottlenoses that live in cooler latitudes. Some of the Doubtful dolphins are 3.5 m—almost as long as the Wilma Jane. Bottlenose dolphins in the tropics usually grow to only 2.5 m.
Appendages such as flippers and fins are smaller in the Doubtful Sound dolphins relative to those from warmer areas—another measure to reduce heat loss. The surface water in sheltered parts of Doubtful Sound may freeze in winter, and, conversely, may reach 25° C in summer.
Paralleling human communities, bottlenose dolphins differ in their daily routines and customs according to the seasonal environment. Newborn dolphins have a high surface area-to-volume ratio, making them more susceptible to the cold than adults are. Whereas bottlenose dolphins in warm waters breed year-round, the Doubtful pod has a seasonal breeding pattern in which births occur in summer. Because the gestation period in bottlenose dolphins is 12 months, conception also occurs in summer, and during January, February and March Crooked Arm becomes a cross between a baby’s cradle, a sporting arena and a bordello.
Courtship and mate selection also seems to differ in the Doubtful pod, in that dolphins establish long-term cross-gender associations—what might be described anthropomorphically as “relationships.” Warm-water populations of bottlenose dolphins, by contrast, tend to be promiscuous. Males band together to separate a single female from her group, and then mate with her.
In Doubtful Sound, males are thought to compete for the attentions of a female by seeking to jump higher than their comrades. Other less flamboyant displays are also thought to impress females, such as males carrying pieces of seaweed on their beaks.
Until recently, flying head butts and other aerial displays were thought to be competitive sparring displays performed by males to show their sexual prowess to nearby females. However, new work shows that younger sub-adult and juvenile males perform most of the leaping and head-butting during summer. These males are unlikely to be sexually active, so the aerial activity may be associated with establishing rank in the male hierarchy. Perhaps such displays can be compared with pre-season trials for a school’s first-15 rugby team as opposed to similar trials for a senior club side. You can guarantee there will be more interest shown by schoolgirls in the selection of the school team than those older (though undoubtedly stronger and faster) men who play for a club. This is because the school team falls inside the female students’ peer group. The boys’ displays may be the first step to impressing a female of similar age and a way of beginning a longer-term relationship.
I first visited Doubtful Sound at the end of summer, when the juvenile males were still frisky. Once, during our daily search for dolphins, Lusseau spotted a group of juvenile males head-butting and crashing into each other. Even from a distance it was obvious that each jump was an expression of youthful physicality and confidence.
Five or six young males were playing some sort of game, the rules and purpose of which were hard to fathom. It seemed to be a hybrid between boxing and ballet. One minute they were swimming in synchrony, the next they were flying full tilt at each another. Occasionally the timing was such that they would avoid a mid-air collision. Other times a bone-crushing thud echoed across the water.
The relevance of the visible above-water part of these displays is difficult to interpret with accuracy because little is known about what happens under water afterwards. Visibility in the dark water is often less than five metres.
There are plans to test the importance of male-female associations using DNA studies to establish the paternity of calves. Once the fathers are known, researchers will be able to reanalyse behavioural data and gain greater understanding about the roles of friendship and display.In addidtion to differences in size and reproductive behaviour, the Doubtful Sound dolphins have quite different social structures from those of other pods.
Elsewhere in the world, bottlenose dolphins operate within a social structure known as a fission-fusion society. A major feature of these societies is that larger groups disperse into small groups—normally with 10-15 members—and recongregate later in the day. Associations are based on age and sex, with females living in natal bands and males roaming between groups. The Doubtful Sound dolphins present a different structure. They form The Doubtful Sound dolphins present a different structure. They form larger groups with an average of 26 members, and the sub-groups have a mix of all ages and both sexes.
Generally animals congregate into large groups for two reasons: to improve success during cooperative hunting and to confuse predators. Although no one has ever seen a shark attack dolphins in Doubtful Sound, they are thought to be the dolphins’ only predators. During a dive, Schneider found the corpse of a sub-adult male, which appeared to be the victim of a shark attack. “NIM23 was a seven-year-old male,” says Schneider. “When I found him he had big bites taken out of his side. Around the time of his death we actually found a dead shark in a tree, shredded to bits. So who knows what kind of drama occurred.” Despite the presence of sharks, their impact appears to be minimal; in fact, the low predator threat is probably one of the main attractions of Doubtful Sound.
Having spent so much time with the dolphins, Schneider is convinced that they have individual personalities. “There is just something in the way they swim. MiVI23 was subdued and quiet. Then there was one I called Thumper. He got this mad look in his eye before going under the boat, and then he would start slapping the hull with his tail fluke. Sure, they have personalities. Getting to know them gave me a real kick.”
Personalities apart, the most significant part of Schneider’s study involved uncovering the social dynamics of the dolphins. He found that nursery pods usually consist of a group of females at various stages of maturity, including mothers with their calves. Juvenile females are sometimes given the role of baby sitter, but it is grandmothers that play the pivotal role.
Over the three years of Schneider’s study, five dolphins occupied the central position within the pod. Four were confirmed to be female, and the fifth was not sexed. “Two of the popular dolphins slowly moved to the edge of the pod and were replaced in my study,” says Schneider. “Each of them was replaced by another large and probably old female. The analysis of associations led me to believe that the community is matrifocal.”
Some researchers believe that grandmother dolphins are responsible for passing on important “cultural” knowledge, while mothers teach socially acceptable behaviour. While I was with the nursery pod a mother brought her infant to the surface and turned it upside down and lifted it out of the water on her beak. The calf flapped away and seemed very disturbed. When Lusseau saw this he shouted excitedly, “Look! She is schooling her calf.”
“Schooling?” I asked.
“This is not a scientific term. When the Mafia punish someone they call it `schooling.’ When a mother lifts her calf out of the water she is chastising it. The calf was jumping in the path of other dolphins.” This is apparently unacceptable behaviour for calves in dolphin society. In captivity, mothers have been seen punishing their calves in three ways: by holding them above water, by holding them on the bottom or by giving them a sonic burst.
The next day I was treated to more displays of dolphin exuberance. Close to Secretary Island I saw four dolphins playing with a buoy. Crayfish potting is the only form of commercial fishing in Doubtful Sound, and the position of each pot is marked by a bright buoy. As I was watching the dolphins, one of the buoys began bouncing up and down as if something were tugging on it. Eventually the buoy disappeared under water. A couple of seconds later it bobbed back to the surface, then a moment later a dolphin leapt into the air, completing a forward summersault only a couple of metres away from it.
This happened maybe a dozen times. The buoy would disappear, resurface, then, with an explosion of water, a dolphin would leap skyward. I could not see what was happening below the surface, nor could I see how deep they were, but it seemed that the object of the game was
On a separate occasion when we were following a group, three dolphins broke away and went to one of the few shallow bays in Doubtful Sound. They swam so close to the shore that they nearly stranded themselves. Half of their bodies exposed, they thrashed around for a few seconds. Lusseau explained that they were rubbing themselves on the pebbly surface to scratch off loose skin or to remove parasites. Then the actions changed from a thrashing action to a more focused rub. One dolphin lifted its beak out of the water and rolled slightly to one side. To me it looked like it had found the itchy spot it wanted scratched—and did I just imagine the look of intense satisfaction on its face?
New Zealand legislation protects the complete landmass of Fiordland National Park but leaves most of the fiords unprotected. Dolphins, like all cetaceans in New Zealand, are protected, but this is not the case for their environment or the prey they feed on. Karsten Schneider harbours particular concerns about the growth in dolphin tourism, and the potential for disturbance of the Doubtful pod. “Since I started my work a lot has changed. There are more tourist operators and many more private boaties going fishing.”Schneider thinks recreational fishers may compete directly with the dolphins for scarce resources. “Fiords are a very low-productivity ecosystem,” Schneider explains. “There is probably enough food for a pod of maybe 80 dolphins. At present, dolphins are the major predators in Doubtful Sound, and if they face increased competition for limited prey resources, then they will have to look elsewhere for food.”
Among the recreational activities that are increasing in Doubtful Sound is sea kayaking, which Lusseau suspects is not a dolphin-friendly activity. “Studies on the impact of tourism on seals have shown that sea kayaks cause more stress to the animals than other vessels do,” says Lusseau, “It is known that seals can hear boats with engines coming from a distance, but kayaks move silently through the water and often surprise and stress them. Dolphins may react in the same way.”
Early findings in Lusseau’s work show that there are noticeable changes in the dolphins’ jumping when boats are around. “Last summer in Milford Sound lots of boats had been with the dolphins, and we started to see adults jumping up to three body lengths in height. In some of the bigger dolphins this is up to 12 m. It was a pretty impressive sight. I have never seen dolphins jumping that high in Doubtful Sound. After this display, the dolphins headed out of the sound—which is most uncharacteristic.
“In Doubtful Sound we have a really special population, even for Fiordland, and I think we have to protect it. We have to make sure they do not start leaving the fiord. We have already had several occasions when there has been some unusual movement of the population that has not been seen before. They just break off from their normal activity and head to the mouth of the fiord. Is this just a freak occurrence, or an early warning? I think we have to take a cautionary approach.”
It would certainly be a tragedy if this pod were to be broken up, or lost altogether, as a result of human interference. My last few hours with the dolphins were particularly memorable. We were completing a final sweep of Thompson Sound, the sun falling below Mt Grono ridge. I’d had a frustrating afternoon, with the Wilma Jane being tossed around by strong winds and a steep swell. We were about to head home when Lusseau sighted a small group frolicking in the upper, sheltered reaches of the sound, where the waters were glassy and the reflections superb. We followed the dolphins as they darted in and out of sight beneath our bow.
As we travelled, the group we were following met up with other sub-groups. Suddenly we had all the dolphins of Doubtful Sound socialising, chasing each other and jumping in front of the boat. After a few minutes, they all turned back down the sound as one body. It seemed as if a race had begun.
The sky reddened and the mountaintops glowed auburn with the last of the day’s light. Sixty dolphins were charging down Thompson Sound, leaping and celebrating. Several took turns on the bow of Wilma Jane. Through the purple-black water I again saw the smiling beak and inquisitive eye of a dolphin looking up at me. It’s hard not to interpret such an encounter on human terms, and it seemed to me at that moment that there was nothing this animal expected of me. He had not been trained to depend on me for food. He had no expectation of affection, no desire to point me down the path to enlightenment; nor did he appear to have any wish to communicate. He came to the boat solely to satisfy his own inquisitiveness. He was totally confident. Contented. At home and, for now, without threat.