Dolphins can Talk like Humans

While it was always believed that dolphins communicate with each other by whistling, a new study suggests that the whistle like sound made by dolphins is closer to the way humans ‘talk’. The research team from Aarhus University says that the whistle sound produced by dolphins originates in much the same way as human sounds are produced by the vocal chords.

Peter Madsen, a researcher at Department of Biological Sciences at Aarhus University  and his team found that the dolphin sounds are produced by tissue vibrations just as the vibration of vocal chords results in sounds in humans and other land animals.

To understand the difference, the researchers noted first how whistle sounds are produced.

“When we or animals are whistling, the tune is defined by the resonance frequency of some air cavity,” said Peter Madsen.”The problem is that when dolphins dive, their air cavities are compressed due to the increasing ambient pressure, which means that they would produce a higher and higher pitch the deeper they dive if they actually whistle.”

They then digitized and reanalyzed recordings made in 1977 of a 12-year-old male bottlenose dolphin. The dolphin breathed in a ‘heliox’ mixture which is 80 percent helium and 20 percent oxygen. In humans this mixture results in producing ‘Donald duck’ like sounds as the mixture has a sound speed 1.74 times higher than normal air. If someone whistles in the heliox air the pitch of the whistle would therefore be much higher than normal air.

But the researchers interestingly found that the dolphin’s whistle pitch did not change. This helped them conclude that the dolphins do not whistle rather they talk using the connective tissues in the nose to vibrate.

“We found that the dolphin does not change pitch when it is producing sound in heliox, which means that its pitch is not defined by the size of its nasal air cavities, and hence that it is not whistling,” Madsen said. “Rather, it makes sound by making connective tissue in the nose vibrate at the frequency it wishes to produce by adjusting the muscular tension and air flow over the tissue.”

“That is the same way that we humans make sound with our vocal cords to speak,” he added.

The researchers also add that the same is true in the case of toothed whales as well as they too have the problem of communication when they are diving.

On what they might be communicating about, the researchers feel it may be giving their identity and helping stay connected in while travelling in large groups in water.

Acoustics engineer John Stuart Reid and Jack Kassewitz of the organization Speak Dolphin have created an instrument called CymaScope that helps to study dolphin sounds using pictures.  This can be used to decipher the exact meaning of the different sounds made by dolphins including the series of chips and click trains produced by them.

“There is strong evidence that dolphins are able to ‘see’ with sound, much like humans use ultrasound to see an unborn child in the mother’s womb,” Kassewitz  said. “The CymaScope provides our first glimpse into what the dolphins might be ‘seeing’ with their sounds.”

He added, “I believe that people around the world would love the opportunity to speak with a dolphin. And I feel certain that dolphins would love the chance to speak with us — if for no other reason than self-preservation.”

Madsen and his team also say in their research that animals can evolve a trait, lose it and then learn it again because the land based ancestors of dolphins did communicate with each other. When they became marine animals they forgot the way to communicate but re-learned a more advanced form.

The researcher also says that dolphins can be made to learn whistling but they will not usually use it to communicate with other dolphins in the wild. For that communication they will prefer the much more effective way to make sound that they have evolved.