We humans love to call each other names. We have our given names, of course, along with nicknames, pet names, and even some nasty, insulting names. Up until very recently, scientists thought that we were the only animals that actually gave names to ourselves or other members of our species. But a new study published today in PNAS shows that bottlenose dolphins are the first animals known to assign names to individuals in the wild.
Although humans start naming things almost as a matter of course during early development, the process of creating and using a name is actually quite complex. Scientists refer to names as learned vocal labels, meaning vocalizations that refer to specific objects. Both parrots and dolphins have used learned vocal labels while in captivity, and researchers had no reason to believe that the animals couldn’t do the same in their natural environments. Now biologists Stephanie King and Vincent Janik from the University of Aberdeen have found that, indeed, wild dolphins use the equivalent of a human name to address each other.
A variety of vocalizations
Dolphins in particular have an unusual array of vocalizations that researchers have recorded in wild populations. A key part of a dolphin’s vocal repertoire is the signature whistle, which are distinctive whistles unique to a particular dolphin. Recordings of wild dolphin pods indicate that these signature whistles comprise up to two-thirds of a dolphin’s vocalizations.
To create these unique calls, dolphins vary the frequency of the sound waves they produce, similar to the creation of an FM radio signal. Previous work found that dolphins, like humans, need to learn how to produce their vocalizations. Typically, a dolphin creates its own signature whistle by combining and rearranging components of other dolphins’ whistles and calls.
Dolphins called by name
The unique nature of the signature whistle hinted that they could be used as a way for dolphins to recognize each other, but the idea had never been formally tested. In the waters off of eastern Scotland, King and Janik recorded the signature whistles of 12 dolphins. Shortly after they recorded the whistle, the played it back to the same dolphin and recorded its response. They also recorded the response of the dolphin to the signature whistles from other dolphins in the pod and from dolphins in different pods.
When the dolphins heard their own signature whistle, 8 of the 12 dolphins called back with various vocalizations. However, only two of the 12 dolphins also replied to the signature whistle of their fellow pod members, while the signature whistle of unfamiliar dolphins elicited no reply. The researchers believe the reply vocalizations may have been responses by the dolphin to hearing its “name” used by its close companions. King and Janik also couldn’t rule out the responses of other podmates to hearing a familiar signature whistle.
Together, these results indicate that a dolphin’s signature whistle may provide a way for dolphins to communicate with a specific individual. In this sense, the signature whistle seems to function in a similar manner to a human name. Still, it’s thought to be pretty rare that dolphins copy another individual’s whistle under natural circumstances. Thus it seems dolphin names are used primarily by their owners as a way to self-identify, rather than by their companions.
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