Female bottlenose dolphins whistle at a higher pitch when they communicate with their calves, mirroring the “baby talk” used by humans. This behaviour could help to enhance bonding and learning in dolphin calves.
When people interact with babies, they often speak in a high-pitched, sing-song cadence. This modified speech pattern is common to nearly all human cultures and vocal languages.
Bottlenose dolphins produce a distinctive whistle unique to each individual, known as their signature whistle.
“For a long time, I’ve been interested in dolphin mother-calf communication, which could help us understand the process of how they develop their signature whistles,” says Laela Sayigh at Woods Hole Oceanographic Institution in Massachusetts.
To test whether their signature whistles change when they communicate with their offspring, Sayigh and her colleagues analysed the whistles of 19 adult female common bottlenose dolphins (Tursiops truncatus) in waters near Sarasota Bay, Florida, that were recorded over a 34-year period, both with and without their calves.
They found that when dolphins were with their offspring, they produced whistles with a higher frequency, or pitch, and a much wider range of frequencies than at other times.
“The modified whistle still conveys the identity of the animal,” says team member Frants Jensen at Woods Hole Oceanographic Institution. “The subtle shift in the highest frequency that the dolphins use mirrors the pitch shifts we see in humans.”
As in humans, these modified vocalisations could help to promote vocal learning in dolphins, says Jensen, but they don’t have evidence for this yet.
Studying how animals communicate with their young could provide more insight into the evolutionary history behind vocal learning in animals, and ultimately language in humans, says Sayigh. “It is absolutely essential to have basic knowledge about other species and how they communicate.”
“I would be really interested to see whether dolphins also change their whistles when interacting with babies of others, which is what happens in humans,” says Julie Oswald at the University of St Andrews, UK.