A recording of human-like sounds made by a whale almost 20 years ago may have been an example of vocal learning, according to a paper published this week in a science journal by a US marine research foundation.
In 1984, handlers at the National Marine Mammal Foundation in San Diego, California, heard mumbling coming from a tank containing whales and dolphins that sounded like two people chatting far away.
Researchers realised the source of the sound after a diver surfaced from the tank and asked: "Who told me to get out?" The garble came from a captive male Beluga whale named Noc.
"The whale's vocalisations often sounded as if two people were conversing in the distance," said Dr Sam Ridgway, president of the National Marine Mammal Foundation.
For several years, the foundation recorded its spontaneous sounds while it was underwater and when it surfaced.
An acoustic analysis revealed the human-like sounds were several octaves lower than typical whale calls. The research paper has been published in the science journal Current Biology.
"When Noc matured, we no longer heard speech-like sounds, but he did remain quite vocal," Dr Ridgway said.
Scientists think the whale’s close proximity to people allowed it to listen to and mimic human conversation. It did so by changing the pressure in its nasal cavities. After four years of copying people, it went back to sounding like a whale, emitting high-pitched noises. It died five years ago.
“While it’s been a number of years since we first encountered this spontaneous mimicry, it’s our hope that publishing our observations now will lead to further discoveries about marine mammal learning and vocalization. How this unique ‘mind’ interacts with other animals, humans and the ocean environment is a major challenge of our time,” Dr Ridgeway said.
Dolphins and parrots have been taught to mimic the patterns of human speech, but it is rare for an animal to do it spontaneously.
The study is not the first time a whale has sounded human.
Scientists who have studied sounds of white whales in the wild sometimes heard what sounded like shouting children. Caretakers at the Vancouver Aquarium in Canada previously said they heard one of the white whales say its name.
Additional reporting: AP