Do Dolphins Have Names? How Signature Whistles Work

Bottlenose dolphins do have something very close to names. Each dolphin develops its own "signature whistle", a sound pattern that identifies it, and other dolphins sometimes copy that whistle when they want to reach that particular individual. Research from the University of St Andrews, published in 2013, showed that these copies are made mostly by close companions, and a follow-up study found that wild dolphins answer when they hear their own whistle played back to them.

That does not mean dolphins chat like people. But it does make them one of very few animals known to use learned sounds to label one another. Here is how signature whistles work, what the key studies found, and where the comparison with human names holds up.

What a signature whistle is

Dolphins make several kinds of sounds. Rapid clicks are used for echolocation, the natural sonar that lets them "see" objects and prey with sound. Burst pulses and squeaks carry social meaning. Whistles, the long tonal sounds we usually picture, are where identity comes in.

A signature whistle is a whistle type with its own distinctive rise-and-fall frequency pattern, or contour, that dominates one animal's repertoire. Calves usually settle on their signature within their first year, shaping it from the sounds around them. Some male calves model theirs on their mother's, but most end up clearly different from their close companions, which makes sense if the goal is to be recognised.

Once formed, a signature whistle can stay stable for at least 12 years. Dolphins have even recognised the whistles of former companions after more than 20 years apart, which is among the longest social memories recorded in any animal other than humans.

Importantly, identity is carried by the shape of the whistle, not by the tone of the voice. That is different from most animals, which recognise each other by voice quality, much as we recognise a friend on the phone. A dolphin's whistle is closer to a word: it still means "this individual" even when another animal produces it.

The 2013 copying study: who calls whom

The first study behind the "dolphins call each other by name" headlines was led by Stephanie King of the Sea Mammal Research Unit at St Andrews, working with Vincent Janik and US colleagues including Laela Sayigh and Randall Wells. It was published in Proceedings of the Royal Society B in 2013.

The team used more than 200 hours of recordings made between 1984 and 2009 of wild dolphins in Sarasota Bay, Florida. The animals were held briefly, in separate spots, during health checks by a long-running research programme, so they could often hear one another but not see each other. The researchers also recorded four adult males at an aquarium in Florida.

Copying turned out to be rare. It showed up in 10 of 179 pairs of animals, mostly between mothers and calves and between males in alliances, the close partnerships that adult males form. Copiers were strongly associated with the animal they copied. The copies kept the overall shape of the original but differed in some details, so they did not pass as the real thing. That suggests copying was not used to deceive or to threaten.

King summarised the meaning in the press coverage: animals made copies when separated from a close associate, which supports the idea that a dolphin copies another's signature whistle when it wants to reunite with that specific individual.

The playback experiment: dolphins answer to their "name"

Copying alone does not prove that the target understands it is being called. So King and Janik ran a second study with wild bottlenose dolphins off the east coast of Scotland, published in PNAS later in 2013.

They identified each animal's signature whistle and then played back one of three sounds through an underwater speaker: a computer-generated version of the dolphin's own whistle, the whistle of a familiar animal from the same population, or one from an unfamiliar population. The dolphins responded, often by whistling back, only to the synthetic copy of their own signature. Because the copy was made by a computer, it was the pattern, not a familiar voice, that they reacted to.

Janik described the result as "the first case of naming in mammals, providing a clear parallel between dolphin and human communication."

Why dolphins need names at all

Bottlenose dolphins live in what biologists call fission-fusion societies. Groups of around 15 are typical, but they constantly split and merge, sometimes with pods of a hundred or more coming together for a while. Mothers and calves, and allied males, can be separated in murky water where sight is little use.

In that world, a sound that says "it's me" and another that says "I'm looking for you" are extremely useful. Wild dolphins use their signature whistles mainly when they are apart from their group, and mothers even shift their whistle to a higher pitch when their calf is near, a little like the sing-song voice people use with babies.

Sound also travels well underwater. Whistles have been estimated to be audible to other dolphins over many kilometres in good conditions; earlier reports put the maximum at around 20 km, although the real range depends heavily on depth, background noise and frequency, and is usually far shorter.

How far the "name" comparison goes

It is fair to call signature whistles names in a functional sense: a learned sound, unique to one individual, which others can use to address that individual. Very few animals are known to do this. Some parrots and, according to more recent research, elephants and marmosets may use comparable labels, but the dolphin evidence is among the strongest.

What the studies do not show is a full language. There is no evidence that dolphins combine names with other learned "words" into sentences, or talk about absent individuals. Captive dolphins have learned artificial signals for objects in experiments, which shows the capacity to attach sounds to things, but that is a laboratory skill rather than proof of wild conversation.

The research also has a practical side. Signature whistles let scientists count and track individuals with underwater microphones, and noise from ships and construction can mask exactly these calls, making it harder for mothers and calves to find each other.

Key points to remember

• Each bottlenose dolphin develops a unique signature whistle, usually in its first year.
• Close companions sometimes copy each other's whistles, especially when separated.
• Wild dolphins respond to synthetic versions of their own whistle, but not to other whistles.
• This is naming in a functional sense, not evidence of human-style language.

This page first shared the news in 2013 via the tech blog Wordless Tech, which summarised a Discovery News report on King's study; neither original page is still online.

Sources: King, Sayigh, Wells, Fellner and Janik (2013), Vocal copying of individually distinctive signature whistles in bottlenose dolphins, Proceedings of the Royal Society B; University of St Andrews: Dolphins respond to individual names; Wikipedia: Signature whistle; Wikipedia: Common bottlenose dolphin.

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