Signature Dolphin Sounds Show Advanced Communication

by Belinda Recio

Scientists have recently made exciting progress in starting a conversation with dolphins
Humankind has always had a soft spot for dolphins, no doubt because these sleek, athletic marine mammals are social, playful and seem to genuinely like people. And then there are the stories about dolphins guiding ships to safety, assisting fishermen, playing with children and saving people from drowning.
In the 1950s, dolphins began to capture the human imagination for new reasons: their ability to use echolocation to find and assess objects, their intelligence and the possibility of interspecies communication with them. In the 60 years since dolphins leapt into the limelight, scientists have learned a lot about these charismatic animals.
To start with, dolphins appear to have self-awareness based on their response to the mirror test—an assessment that measures whether an animal can recognize its own reflection. They are also altruistic (they tend to the ill and injured), cooperative (they divide labor), promiscuous (they engage in sex frequently, and not just for mating), and capable of aggression (males will bully and worse). Dolphins enjoy games, such as creating and manipulating underwater bubble rings, and playing “keep away” with strands of seaweed. They also participate in interspecies play with whales, dogs and humans.
In captivity, dolphins can learn complicated tricks and long strings of commands. In the wild, they engage in tool-using behaviors, such as wrapping bits of sponge around their beaks—as protection from rocks and broken coral—when foraging on the sea floor. Researchers even observed mother dolphins teaching the sponge technique to their young, suggesting that dolphins pass down knowledge. And, based on preliminary observations of dolphins using a complex echolocation technique, it looks like they might be capable of addition, subtraction, multiplication and ratio comparisons.
Science has learned all this and more about dolphins, yet they still haven’t figured out a way to communicate with them. But just as a journey of a thousand miles begins with a single step, a conversation often begins with the exchange of names, and this is where scientists have recently made some exciting progress. Recent research into signature dolphin sounds has revealed a complicated communication process.
When a bottlenose dolphin is just a few months old, he develops a unique pattern of notes that becomes his “signature whistle,” and no two signature whistles are alike. It appears that juveniles develop their signature whistles by listening to, learning from and modifying the calls of other dolphins, usually family members. Dolphins mostly vocalize their own whistle, but sometimes mimic one another’s whistles.

In a recent study, researchers found it seemed like dolphins were calling out their signature whistles in the same way that humans use names.

Marine biologists Stephanie L. King and Vincent M. Janik, from the University of St. Andrews in Scotland, were curious about whether the signature whistles might be functioning as “names” that dolphins use to announce themselves and address one another, so they and their colleagues embarked on two studies.
In their first study, the researchers recorded the whistles of captive and wild dolphins in Florida. They discovered that only dolphins with close social bonds mimicked each other’s signature whistles, and that the mimicking tended to occur when the bonded dolphins were separated. It seemed like the dolphins were calling out their signature whistles in the same way that humans use names.
In their second study, the researchers followed different groups of wild dolphins off the coast of Scotland for more than four months. They identified and recorded each individual’s signature whistle. Using software, they then created synthetic versions of the whistles, in order to remove the specific vocal qualities that might identify the dolphin that vocalized.
For example, imagine a recording of your mother’s voice saying your name. Your response would likely be a reaction to recognizing your mother’s voice as well as to hearing your name. Now imagine a “robot” voice saying your name. Your response would be only to hearing your name, not a specific human voice. By neutralizing the vocal tones, the researchers could be certain that when the dolphins heard the recordings, they would hear the “message” and not the “speaker.”
King and Janik observed the dolphins’ responses to three kinds of synthetic signature whistles: their own signature whistle, the whistles of dolphin “friends” and the whistles of dolphin “strangers.” When a dolphin heard its own signature whistle—its “name”—it whistled back. The other two synthetic whistles—those of friends and strangers—didn’t elicit much of a response. Some dolphins, after hearing their own signature whistle, even approached the research boat, as if to say, “You called?”
The researchers speculate that signature whistles are used in the same way that we use names: to initiate contact (“My name is Jack, what’s your name?”), to help lost dolphins reunite (“Hey Jack, where are you?”) and to help calves recognize their mothers (“Mom, is that you?”). As to whether two or more dolphins might use signature whistles to refer to non-present dolphins (“Did you hear about Jack?”), more research is needed. Although researchers are still far from being able to have conversations with dolphins, at least now they will be able to start a conversation by greeting them by name.

Belinda Recio, recipient of the Humane Society’s Award for Innovation in the Study of Animals, owns True North Gallery  in Hamilton, MA, where she exhibits art that connects people with animals and the natural world.

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