WASHINGTON — You know instantly when someone is speaking to an infant or small child. It turns out that dolphin mothers also use a kind of high-pitched baby talk.
A study published Monday found that female bottlenose dolphins change their tone when addressing their calves. Researchers recorded the signature whistles of 19 mother dolphins in Florida, when accompanied by their young offspring and when swimming alone or with other adults.
The dolphin whistle is a unique signal, similar to calling their name.
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“They use these whistles to keep track of each other. The birds are saying “I’m Here, I’m Here” repeatedly, according to Laela Sighy, Woods Hole Oceanographic Institution’s marine biologist.
The mother’s pitch and range are higher than normal when she directs the signal towards her calves. This study was published in Proceedings of National Academy of Sciences.
“That was true for every one of the moms in the study, all 19 of them,” said biologist Peter Tyack, a study co-author from the University of St. Andrews in Scotland.
Obtaining this data was no simple feat. Over more than three decades, scientists placed special microphones multiple times on the same wild dolphin mothers in Florida’s Sarasota Bay to record their signature whistles. This included both years where they gave birth to calves, as well as years without. Dolphin calves in Sarasota stay with their mother for a minimum of three years and often longer. Fathers don’t play a prolonged role in parenting.
“This is unprecedented, absolutely fantastic data,” said Mauricio Cantor, an Oregon State University marine biologist who was not involved in the study. “This study is the result of so much research effort.”
Why people, dolphins or other creatures use baby talk isn’t certain, but scientists believe it may help offspring learn to pronounce novel sounds. Research dating back to the 1980s suggests that human infants may pay more attention to speech with a greater pitch range. Female rhesus monkeys may alter their calls to attract and hold offspring’s attention. Zebra finches can also slow their song down and raise their pitch to speak to chicks. This could make it easier for them to learn bird songs.
For the dolphin study, the researchers focused solely on the signature call, so they don’t know if dolphins also use baby talk for other exchanges — or whether it helps their offspring learn to “talk” as it seems to do with humans.
“It would make sense if there are similar adaptations in bottlenose dolphins — a long lived, highly acoustic species,” where calves must learn to vocalize many sounds to communicate, said Frants Jensen, a behavioral ecologist at Denmark’s Aarhus University and a study co-author.
Another reason to use specific pitches could be to attract the attention of children.
” It’s important that a baby calf knows “Oh, Mom’s talking to me right now” __ rather than just being told she is there by someone else,” said Janet Mann, an independent marine biologist from Georgetown University.
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Follow Christina Larson on Twitter at: @larsonchristina
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