Signature Whistles in Bottlenose Dolphins

Bottlenose_Dolphin-030513New findings published in the Proceedings of the Royal Society B suggest that bottlenose dolphins use “signature whistles” to identify themselves and are able to learn and recognize the “names” of other dolphins. This cognitive ability, known as “referential communication with learned signals,” was always thought to be unique to humans.

In an ongoing study that originated in 2006, a team of scientists reviewed the results of research originally done by the Sarasota Dolphin Research Program (SDRP) from 1984-2009, in which wild dolphins were temporarily captured and then held separately. The dolphins were confined in a manner that allowed them to hear, but not see, one another. The original study also used four already captive dolphins in addition to the ones they captured.

The audio recordings revealed the frantic calls of the trapped dolphins. Some of the vocalizations were copies of their pod mates’ signature whistles, and were an apparent effort to stay in contact with each other throughout their stressful capture.

dolphin-signature- calls-020513
Spectrograms showing three examples each of the (i) signature whistle of the animal being copied, (ii) signature whistle copies and (iii) the signature whistle of the copier.

In the original study done at SDRP, most of the dolphins were separated mothers and calves. The male dolphins studied also mimicked signature whistles from animals who were known to be close associates. This suggests, the new study asserts, that these calls were not made in an aggressive manner (a la bird chatter) but were more akin to calling out for a missing child or lost friend.

However, the dolphins did not precisely replicate each other’s signature whistles. The new research reveals, "fine-scale differences in some acoustic parameters" were added as variations to the original.

According to the research team, these new findings seem to suggest evidence of a dolphin dialogue. They are cautious about calling it a “language”, and say that further studies are needed in both dolphins and other species:

"It is possible that signature whistle copying represents a rare case of referential communication with learned signals in a communication system other than human language. Future studies should look closely at the exact context, flexibility and role of copying in a wider selection of species to assess its significance as a potential stepping stone toward referential communication."

Note: The Nonhuman Rights Project does not endorse experimentation on captive animals. However, we do quote the results of these experiments when they help make the case that the animals have a level of sentience, self-awareness, and, in some cases, theory of mind, that demonstrates they should not be being kept in captivity in the first place.

Leave A Comment