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Why Did These Sperm Whales Adopt a Disfigured Dolphin?

This story was originally published in our Sept/Oct 2022 issue as “A Pod’s Bond.” Click here to subscribe to read more stories like this one.


Legs trailing in the water, I gripped the side of the boat, alert for my cue. As we rose to the top of a swell, the skipper spotted something in the distance and killed the engine. “Go, go, go!”

I dropped with my buddy into the Atlantic Ocean, its floor thousands of feet below us. A moment later, the boat was gone. We were alone. The water was as clear as the air above us; I felt a sense of vertigo as I floated above the abyss. All I could do was wait and hope. Then a huge shape appeared on the edge of my vision against the blue, and another, and another. Gradually the shapes became more distinct as they headed straight at me. I hung in the water, electrified by the sight — the largest predators on the planet, the fearsome protagonist of perhaps the most famous seafaring novel of literary history, Moby Dick.

I was face to face with sperm whales. I was in the Azores to study the social behavior of whales and had gone there with some trepidation. Although this group of mid-Atlantic islands has a resident population of sperm whales, making it one of the best places in the world for biologists to study them, the Azorean relationship with whales has not always been a harmonious one. Whaling was for many years an important part of the culture here, continuing until 1984. Although 27 years had passed since the end of whaling in the Azores, it was likely that adult sperm whales in the region would have experience of humans as hunters. Reason enough, I supposed, for these intelligent beasts to be cautious, or even aggressive, when encountering us in the water.

Over the past half-century, there has been a sea change in the way we appreciate whales — as well as their fellow cetaceans, dolphins and porpoises. Although our historical relationship as predators and prey is regrettably continuing in some parts of the globe, most people now have some understanding of how complex and fascinating these creatures are, and know they are imbued with an intelligence that overreaches that of almost every other species on the planet. In their societies, we see compelling and enduring relationships, sophisticated interactions, and strong evidence of an animal culture.

(Credit: Illustrations by Discover/Kellie Jaeger)

Diving Deeper

When our team of four headed out from the Port of Madalena for the first time, however, we had only the most tantalizing glimpses of the whales as they disappeared into the blue. The small boat we were using was maneuverable, but it didn’t cope well with the large swells, and finding whales is challenging in rough seas. Each day of that initial period was a carbon copy of the last, washing up and down the Atlantic rollers, eyes peeled on the horizon, the only soundtrack my companion Romain’s periodic, heartfelt retching.

Our prospecting was aided by the gimlet eyes of an ancient mariner, Joao, employed as a lookout and ensconced in a hut halfway up the volcano that originally gave birth to Pico Island. Strange to think that Joao had learned his trade and sharpened his skills by being the spotter for whalers years before. Times had changed, even if his job hadn’t. But for four days, even the experienced Joao struggled to spot any whales in the surging sea. The telltale sign of the whales is their spout, the steamy exhalation of air and bits of other, less agreeable things that are fired out of its blowhole at the end of a dive. A decent-sized whale might launch its gust of moist air above the surface, but amid rough seas, you still need good luck to detect it.

Far below the waves, the whales were feeding. They’re prodigious divers, capable of descending more than a mile into the darkness of the midnight zone for more than an hour at a time. Generally, however, they don’t need to push themselves so hard — it all depends on where they can find their food.

To tip the balance in their favor, especially when hunting larger and more elusive prey, sperm whales coordinate and cooperate. They descend to their feeding grounds in pairs or small groups to form a search cordon, a line of whales spaced over half a mile of ocean, a smart solution for locating clusters of prey. Finding a dense patch of squid is only part of the battle, however. Traces taken from underwater GPS devices mounted on the whales show that they divide to conquer — one whale dives below the squid to cut off their escape to deeper water, allowing the other whales to attack the flanks of the prey group. Nonetheless, our understanding of their hunting, like so many aspects of sperm whale behavior, is in its infancy.

Finally, on the fifth day of our trip, the waves relented. At last, we had a chance. Sure enough, it wasn’t long before we heard the radio crackle into life and an excited voice reeling off directions in Portuguese. The skipper shifted course and told us that a pod of sperm whales lay just over a mile to the northwest. If the whales decided to change course, or to dive, then that was just bad luck. If there were to be encounters, these would be entirely on the whales’ terms. So we expected, at best, a few precious seconds with the whales as they passed — enough, if we were really lucky, to notice a few things, such as identifying marks or scars.

But it wasn’t only the ocean swell that had calmed; the whales, too, seemed in less of a hurry. Rather than cruising past, they lingered, and suddenly we found ourselves at the center of a family frolic. It was a phenomenal experience, greater by far than I’d dared to dream of. I couldn’t simply hang at the water’s surface and enjoy it passively, though; the cavorting whales kept coming perilously close, forcing me to scoot out of their way each time a mighty tail threatened to knock me spinning. The pod was made up of four whales: a huge matriarch more than 30 feet long, a slightly smaller individual about three-quarters her size, and two calves. Wonderful as all this was on its own, there was a cherry on our cetacean cake — with the pod was an adult bottlenose dolphin.

The two species are tolerant of one another, but their different lifestyles and prey preferences mean that they seldom associate. What might have decided the issue was that the dolphin had a pronounced curvature of the spine, twisting its body just behind the dorsal fin. It didn’t look like an injury (there was no scarring), but rather something the dolphin had carried since birth. Nonetheless, it had survived, against the odds, to reach adulthood. It’s possible that the condition hampered its ability to swim at the relentless pace at which bottlenoses typically travel. If so, it would be isolated from the intensely social life of its own kind, and perhaps, as a surrogate, it had joined the whale society.

For the next 20 minutes, the whales kept up a constant dialogue with one another, making their ethereal creaking, knocking, and clicking sounds, while periodically the higher-pitched call of the dolphin could be heard. The whales rolled around in the waves at the surface, the smaller members of the pod circling the huge matriarch. Then, even more astonishingly, the whales began some strange kind of game. The matriarch would open her oarlike lower jaw, and one of the smaller whales would swim into her mouth, its head protruding from one side and its tail sticking out the other. The matriarch would then seem to very gently nibble the smaller whale for a second or two. The nibbled whale would swim clear and circle around to join the back of the queue, and another would maneuver into place for a little of the same treatment.

The bottlenose joined in the fun as well, swimming into the matriarch’s open jaws for its turn and receiving a toothy squeeze. I remained mesmerized by the encounter long after I’d left the whales to their play; it was an incredible privilege to get a close-up perspective of the remarkable social behavior of this little-understood animal.

(Credit: Illustrations by Discover/Kellie Jaeger)

Forming bonds

Back on land, I pondered what it meant for the whales to be held in the matriarch’s mouth for a moment. Maybe there was some parallel with the grooming behavior of primates. While the immediate role of grooming might be to keep the fur glossy and bug-free, more important is what underlies it, the act of building and securing relationships. Lacking dexterous limbs, of course, the whales can’t do this. Perhaps this was their creative way of physically expressing themselves.

Sperm whales live in matrilineal social groups, the core of which is formed by related females, often comprising a grandmother, her daughter, and their offspring. Sons, on the other hand, live in these groups only as juveniles. As they approach sexual maturity, the males break from their social group and adopt a more solitary existence — although it’s not unusual for males to form into loose bachelor groups with one or more other males.

The group we saw that day was a fairly typical example of sperm whale society, so it could be that what I’d witnessed was some maternal attention being paid to the family in the form of a strange cetacean embrace. That the dolphin joined in suggested that it understood no threat was involved, while the fact that the matriarch lavished some attention on the dolphin suggests it was an accepted, though perhaps temporary, member of the group.

Social structures

In many ways, this unusual partnership raised more questions than it answered. For example, how did the dolphin manage to forage, encumbered as it was by its scoliotic spine? Based on its appearance, it was certainly well fed. It couldn’t be foraging alongside the whales, because the dolphin couldn’t match its adopted family’s prodigious dives. Was it catching its own food? Or were the whales providing for it in some way? Sometimes, sperm whales bring their squid prey to the surface with them. Perhaps the dolphin was able to help itself to morsels. This seems a stretch, but however it was nourishing itself, the dolphin appeared to be an accepted member of the group.

It’s a demonstration of the unusual structure of sperm whale society that this could happen. Among many similar mammal groups, to be accepted into the fold you have to be a blood relation. While kinship is important to sperm whales, it’s not the sole determinant of their associations. Genetic examinations of their social bonds reveal that they form long-term relationships with both family members and outsiders. Although the dolphin might have been taking this to an extreme, it suggested a remarkable flexibility on the part of both species.

On the final day of the trip we made one last sortie to the whales. Luck was on our side — it had been four days since we’d first met the sperm whale group with the dolphin, and here they were again, the dolphin still very much part of their scene. Weeks later, after we had left this maritime paradise, we heard that our guides had again seen this group, complete with dolphin. This was a longer-term arrangement than I’d imagined; the dolphin was interacting with the whale social group to a surprising degree. If nothing else, it gave us some idea of the extent of the social tendency of both species, the deep-seated drive to seek and remain in company.



Excerpted from The Social Lives of Animals by Ashley Ward. Copyright © 2022. Available from Basic Books, an imprint of Hachette Book Group, Inc.


Ashley Ward is a professor and director of the Animal Behavior Lab at the University of Sydney, where he researches social behavior, learning, and communication across the animal kingdom. His work has been published in top journals including PNAS, Biological Reviews, and Current Biology.


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