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.

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 is a unique and important signal 鈥� akin to calling out their own name.

鈥淭hey use these whistles to keep track of each other. They鈥檙e periodically saying, 鈥業鈥檓 here, I鈥檓 here鈥�,鈥� said study co-author Laela Sayigh, a Woods Hole Oceanographic Institution marine biologist in Massachusetts.

When directing the signal to their calves, the mother鈥檚 whistle pitch is higher and her pitch range is greater than usual, according to the study published in the journal,

鈥淭hat was true for every one of the moms in the study, all 19 of them,鈥� 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鈥檚 Sarasota Bay to record their signature whistles. That included years when they had calves and when they didn鈥檛 鈥� dolphin calves stay with their mothers for an average of three years in Sarasota, and sometimes longer. Fathers don鈥檛 play a prolonged role in parenting.

鈥淭his is unprecedented, absolutely fantastic data,鈥� said Mauricio Cantor, an Oregon State University marine biologist who was not involved in the study. 鈥淭his study is the result of so much research effort.鈥�

Why people, dolphins or other creatures use baby talk isn鈥檛 certain, but scientists believe it may help offspring learn to pronounce novel sounds. Research dating back to the 1980s suggests that human infants may to speech with a greater pitch range. may alter their calls to attract and hold offspring鈥檚 attention. And Zebra finches and slow down their songs to address chicks, perhaps making it easier to learn birdsong.

For the dolphin study, the researchers focused solely on the signature call, so they don鈥檛 know if dolphins also use baby talk for other exchanges 鈥� or whether it helps their offspring learn to 鈥渢alk鈥� as it seems to do with humans.

鈥淚t would make sense if there are similar adaptations in bottlenose dolphins 鈥� a long lived, highly acoustic species,鈥� where calves must learn to vocalize many sounds to communicate, said Frants Jensen, a behavioral ecologist at Denmark鈥檚 Aarhus University and a study co-author.

Another possible reason for using specific pitches is to catch the kids鈥� attention.

鈥淚t鈥檚 really important for a calf to know 鈥極h, Mom is talking to me now鈥� __ versus just announcing her presence to someone else,鈥� added Janet Mann, a marine biologist at Georgetown University, who was not involved in the study.

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Follow Christina Larson on Twitter at: @larsonchristina

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute鈥檚 Science and Educational Media Group. The AP is solely responsible for all content.

Christina Larson, The Associated Press

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