Two dolphins have been recorded having a conversation for the first time, and scientists are comparing it to conversation between two people.
Researchers have known for many years that dolphins have a high level of intelligence and can communicate within a pack, but a new study, published in the St Petersburg Polytechnical University Journal: Physics and Mathematics, has suggested that dolphins are capable of "highly developed spoken language".
Researchers at the Karadag Nature Reserve, Feodosia, Russia, recorded two Black Sea bottlenose dolphins (Tursіps truncatus) called Yasha and Yana talking to each other in a pool.
They believe dolphins use clicks, whistles and pulses to form 'words' which they string together into sentences in much the same way that humans do.
They also found that each dolphin would listen to a sentence of up to five of these 'words' without interruption, before replying.
"Essentially, this exchange resembles a conversation between two people," the lead researcher, Dr Vyacheslav Ryabov, wrote in the study.
“Each pulse that is produced by dolphins is different from another by its appearance in the time domain and by the set of spectral components in the frequency domain. In this regard, we can assume that each pulse represents a phoneme or a word of the dolphin's spoken language.
“This language exhibits all the design features present in the human spoken language, this indicates a high level of intelligence and consciousness in dolphins, and their language can be ostensibly considered a highly developed spoken language, akin to the human language."
Dr Ryabov says the findings of the study should encourage further research into how we can communicate directly with dolphins.
Professor Gisela Kaplan, an expert in animal behaviour from the University of New England in Armidale, tells SBS Science the study offers a greater understanding of the complex and meaningful vocal communication used by dolphins and may offer new ways to communicate with them.
"I'm impressed by the abstraction and signal quality analysis they have done, and I'm not surprised that they have found so many signals," says Kaplan.
"They've obviously got very good equipment which works under the surface of water and goes up to 100kHz, which is enormous - the limit of human hearing is 20kHz - and they managed to get a range of signals from a pair that communicates closely with each other, that differ in quality and length and structure, and were able to analyse the entire sequence.
"Now that we know how to tune in under water and at a level not audible to human ears, I think communication using basic signals would be possible in their own signals, but I don't think we know enough of it yet."
Professor Kaplan said the results of the study highlight the need to address underwater noise pollution, which is inaudible to humans, but may adversely affect dolphins.
"With all the noises we put in the ocean, some of them, particularly these large engines, produce sounds that are in the ulstrasonic range, and they may distress dolphins and be extremely destructive for dolphin societies," she says.
"Now in wildlife areas and marine parks around Australia [we have] engines designed to be particularly low in noise levels for that reason. So I would hope [more of] that follows."