Researchers in the US have been shocked to discover a beluga whale whose vocalisations were remarkably close to human speech.
While dolphins have been taught to mimic the pattern and durations of sounds in human speech, no animal has spontaneously tried such mimicry.
But researchers heard a nine-year-old whale named NOC make sounds octaves below normal, in clipped bursts.
The researchers outline in Current Biology just how NOC did it.
But the first mystery was figuring out where the sound was coming from. The whales are known as “canaries of the sea" for their high-pitched chirps, and while a number of anecdotal reports of whales making human-like speech, none had ever been recorded.
When a diver at the National Marine Mammal Foundation in California surfaced saying, “Who told me to get out?" the researchers there knew they had another example on their hands.
Once they identified NOC as the culprit, they made the first-ever recordings of the behaviour.
They found that vocal bursts averaged about three per second, with pauses reminiscent of human speech. Analysis of the recordings showed that the frequencies within them were spread out into “harmonics" in a way very unlike whales’ normal vocalisations and more like those of humans.
They then rewarded NOC for the speech-like sounds to teach him to make them on command and fitted him with a pressure transducer within his nasal cavity, where sounds are produced, to monitor just what was going on.
They found that he was able to rapidly change the pressure within his nasal cavity to produce the sounds.
To amplify the comparatively low-frequency parts of the vocalisations, he over-inflated what is known at the vestibular sac in his blowhole – which normally acts to stop water entering the lungs.
In short, the mimicry was no easy task for NOC.
“Our observations suggest that the whale had to modify its vocal mechanics in order to make the speech-like sounds," said Sam Ridgway, president of the National Marine Mammal Foundation and lead author on the paper.
“The sounds we heard were clearly an example of vocal learning by the white whale."
AFP – US marine biologists puzzled by human-like sounds coming from the whale and dolphin tank of an aquarium concluded they were actually coming from a whale.
Anecdotal reports of whales sounding like people are not new. But in this case in San Diego, California, scientists for the first time recorded the utterances, did an acoustic analysis and were surprised to find a rhythm similar to that of human speech, Sam Ridgway of the National Marine Mammal Foundation reported Monday.
The sounds marked quite a feat: whales make sounds via their nasal tract, unlike people, who use their larynx. So this particular white whale had to make some tricky muscular and blowhole adjustments.
“Such obvious effort suggests motivation for contact," said Ridgway, the main author of a study featured in the journal Current Biology. “The sounds we heard were clearly an example of vocal learning by the white whale."
The whale, named NOC, died five years ago.
Ridgway says that back in 1984, he and others started hearing sounds near the whale and dolphin enclosure that recalled two people speaking in the distance, too far away to be understood.
The sounds were later traced to one particular white whale when a diver in its tank came to the surface because he thought he heard colleagues tell him to do so.
NOC had lived among dolphins and other white whales and had often been in the presence of humans.
The whale made human-like sounds for around four years until it reached the age of sexual maturity, Ridgway said.