We’ve known for a while that dolphins use signature whistles to introduce and identify themselves to each other.
But new research from a team at the University of St. Andrews Sea Mammal Research Unit suggests that when pods of bottlenose dolphins meet in the ocean, they exchange whistles in what is, even by human standards, a very complex and sophisticated communication system.
Vincent Janik, an expert in nonhuman animal communication, said that this exchange is about saying more than simply “I’m so-and-so and this is my group.” Rather, it communicates who I am and that “I’m interested in making contact in a friendly way.”
“It’s really the first time that we can pinpoint down two individual groups and how they interact in a vocal domain, which is really cool.”
Dr. Janik and his colleague Nicola Quick studied how bottlenose dolphins off the coast of northeast Scotland, communicate with each other. They followed the wild dolphins and recorded their vocalizations. The recordings showed that the dolphins usually swam together in a group moving slowly and relatively quietly. Then, when another group approached, one or more of the dolphins would start to produce their signature whistles.
“We then hear dolphins from the other group calling back with their own signatures,” Janik said. “And after or during this counter-calling the animals get together as one group and continue swimming together. Shortly after the union of the groups, they become much more quiet again.”
Sometimes, when two pods met up, there would be no whistling, no greetings, in which case, the two groups would simply swim past each other. Because of their ocean environment and the fact that they travel hundreds of miles in search of food, dolphins don’t have the same territorial issues that many land animals have.
No one knows exactly what these exchanges are all about, let alone what the whistles mean. But Janik believes they are a greeting, rather than a warning, since a) dolphins are not territorial and b) any merging of pods that the team observed was friendly, rather than aggressive.
Janik noted that the whistles are almost certainly just a small part of the communication that takes place between the groups. They would also be able to glean extra information about the identity of the approaching pod by using their inbuilt sonar.
“We don’t know whether echolocation works in this way, but it seems like a viable hypothesis,” he said. “In that case, the whistle exchange is more of a greeting ceremony that communicates a friendly intention and is perhaps not needed to identify the group after the first introduction.”
The team also noted that it was usually just one dolphin from each group making the whistle introduction before the other members of the two groups would begin to interact and merge. Janik suggested that one of the dolphins “speaks” on behalf of the whole group. (And this would be by a general group choice since, as far as we know, dolphins don’t have formal social hierarchies.)
Dolphins rely on sound and echolocation more than on sight, in part because the waters they travel are often quite murky. And while they can sometimes only see a few feet in front of them, their whistles, and possibly their echolocations, can be heard or felt over about six miles.
While there have been many studies of communication and language with dolphins in captivity, these are inevitably artificial. They can demonstrate that dolphins understand human language, but give little insight into dolphin language.
“Dolphins are comparable to great apes in their cognitive skills, but all we know is what they do in a lab,” Janik explains. “We wanted to understand how dolphins use their intelligence outside of the tasks that humans set for them.”
(Janik is leery of using the word “language” at all, since it implies a very human communication system, which may be entirely different from the system dolphins have developed.) The new study gives more insight than ever into communication among dolphins in the wild.
“These are wild groups that are just doing whatever they’re doing,” Janik said. “It’s really the first time that we can pinpoint down two individual groups and how they interact in a vocal domain, which is really cool.”
The results of the study are reported in the Proceedings of the Royal Society B.