Female dolphins are also fluent in ‘Mamanhese’ – 06/28/2023 – Science

Like human mothers, female dolphins are also fluent in “motherese”—that particularly delicate, “singing” form of oral communication that adults of our species often employ when addressing babies.

The discovery, made by researchers in the United States who recorded the vocalizations of marine mammals when they interacted with their young and with other dolphins, strengthens the idea that the bond between mothers and their offspring is an important element in understanding the development of vocal communication. and language. While the underwater whistles emitted by dolphins are nowhere near as complex as human language, the parallels are too detailed to be mere coincidence.

The detection of “mamanhês” among cetaceans is described in an article in this week’s edition of the scientific journal PNAS, linked to the US National Academy of Sciences. The study was led by Laela Sayigh, a researcher at the Department of Biology at the Oceanographic Institution Woods Hole (US East Coast).

Sayigh and his colleagues studied a population of bottlenose dolphins (Tursiops truncatus) which has been observed for over 50 years in Sarasota Bay, Florida (the species is also common on the Brazilian coast). During routine temporary captures, which were used to periodically assess the health status of the animals, the scientists took the opportunity to attach small microphones with suction cups to the animals’ foreheads. This allowed obtaining high-quality recordings of the sounds produced by 19 females of the species over decades.

Most crucially, it was possible to compare the recordings when the captured females had young by their side and when they were alone or accompanied only by other adults. This helped the scientists to verify whether, in fact, the presence of the small dolphins (with an average age of two years when they accompanied their mothers) modified the vocalizations coming from them.

In the analysis, Sayigh and his colleagues focused on the so-called signature whistle, a sound that is an individual hallmark of each dolphin and is emitted frequently. There are those who compare this vocalization to the use of personal names among human beings. It turns out that, when they are in the presence of their young, the females of the species emit modified versions of the signature whistle, which have characteristics very similar to the human speech of whoever is using “mamanhês”.

Among these traits is the use of higher sound frequencies—popularly, we would say that female dolphins “talk more finely” to their babies, just like the mothers of our species. Furthermore, the range of frequencies used in the “mamhês” of both species is wider, reflecting the “sung” character of this type of communication.

“There is no consensus as to why ‘mamish’ involves higher frequencies,” Sayigh explained to Sheet. “One proposal is that this type of sound could sound less threatening. But there’s only a limited amount of changes you can make to a given sound, so it could just be coincidence that both humans and dolphins increase the frequency of their vocalizations.”

What is certain is that, at least in our species, this tendency, which is present in practically all cultures, strengthens the bond between mother and baby and can be an important stimulus for the beginning of the use of language. It is still not entirely clear whether these effects are also important for interaction between dolphins, says the researcher.