研究：海豚母亲使用婴儿语来呼唤幼崽

A new study has found that dolphin mothers use different sounds to communicate with their young than those they use with adults.

The research suggests that the use of the special sounds is similar to the way adult humans use so-called "baby talk" with children.

Female bottlenose dolphins change the tone and length of their whistle when calling and communicating with their young, the study found. Male dolphins do not play a big part in raising young.

The so-called "signature whistle" is an important part of communication for dolphins. Researchers say changing the whistle tone permits female dolphins to signal their young that the communication is meant for them. Scientists say the signals are similar to humans calling someone by name.

The research team recorded signature whistles of 19 mother dolphins living in the Sarasota Bay area along the western coast of Florida. Microphones were repeatedly placed on the same wild dolphin mothers to capture the recordings. On average, young dolphins stay with their mothers for about three years in Sarasota Bay.

The research was carried out over a period of more than 30 years. A study describing the findings was recently published in Proceedings of the National Academy of Sciences.

Laela Sayigh is an ocean biologist with the Woods Hole Oceanographic Institution in Massachusetts. She was a co-writer of the study. Sayigh told The Associated Press the animals at times "use these whistles to keep track of each other."

The length and tone of the sounds changed "for every one of the moms in the study, all 19 of them," said biologist and study co-writer Peter Tyack. Tyack is with the University of St. Andrews in Scotland.

Scientists do not know exactly why people, dolphins and other creatures use baby talk to communicate with their young. But they believe it may help the young learn many important sounds.

Research dating back to the 1980s suggests young human babies may pay more attention to speech with a number of different tones. For example, female rhesus monkeys may change their calls to seek and hold a young animal's attention. And zebra finch birds slow their songs and use higher tones to communicate with young.

For the dolphin study, the researchers centered only on the signature call. So they do not know if the animals also use baby talk for other communication — or whether it helps their young learn to "talk" as it seems to do with humans.

"It would make sense if there are similar changes in bottlenose dolphins — a long lived, highly acoustic species," said Frants Jensen. He is a behavioral ecologist at Denmark's Aarhus University and also a co-writer of the study.

Another possible reason for using different tones is so the dolphin mothers can catch the attention of their young, said Georgetown University ocean biologist, Janet Mann. She was not involved in the study.

"It's really important for a (young dolphin) to know ‘Oh, mom is talking to me now,'" Mann said.

I'm Bryan Lynn.

The Associated Press reported this story. Bryan Lynn adapted the report for VOA Learning English.

______________________________________________________________

tone – n. the quality of a sound, especially someone's voice

whistle – v. to make a high sound by forcing air through a small hole in the mouth

keep track – v. follow closely

acoustic – adj. relating to sound and hearing