With us, language development benefits from the typical motherly singsong. Researchers have now discovered the phenomenon of “baby language” in a bat species too: the females of the sac-winged bat also change the sound of their vocalizations, depending on whether they are aimed at young animals or adults. In these socially living animals, with their complex sound communication, this behavior may have a similar function to that in humans, say the researchers.
High voice and slow, overly clear pronunciation: When people speak to small children, they change their communication behavior in characteristic ways. This reaction is particularly pronounced among mothers when dealing with their offspring: They speak in baby language, which is also known as “motherese” in English. A 2017 study showed that women unconsciously change the characteristic timbre of their voice when they experience this phenomenon – regardless of which language group they belong to. Studies have also already made it clear what function the changed way of speaking has: Baby language therefore serves the language development of toddlers. The acoustic characteristics make it easier for them to recognize where a word begins and where it ends. In addition, the special timbre and pitch of baby speech lead to increased attention in the child, research suggests.
Bat mothers overheard
The extent to which there are parallels to this phenomenon in the animal kingdom has not yet been researched, reports Ahana Fernandez from the Museum für Naturkunde Berlin and Mirjam Knörnschild from the Smithsonian Tropical Research Institute in Panama City. While there are numerous examples of special sounds used by mothers to communicate with their young, it is not a concept comparable to the Motherese. So far there have only been indications of an adaptation of the normal vocalization when dealing with young animals in zebra finches and squirrel monkeys. The two scientists have now discovered the phenomenon when investigating the complex communication of the saxophone bat (Saccopteryx bilineata). This is a comparatively well-studied bat species that occurs in South and Central America.
As part of the study, the researchers examined the vocalizations of adult animals from bat colonies in Costa Rica and Panama. They recorded whether the communication between females was directed to their young or to other adult conspecifics. To examine the sound characteristics, they used an analysis technique that was originally developed for human voice recognition in order to work out acoustic characteristics of a voice. These include parameters such as the pitch as well as the timbre of a voice.
As the scientists report, the acoustic analyzes of the communication sounds of the female bats showed that the sound of their voice always changed in a characteristic way, depending on whether they were addressing their young or adult conspecifics. This is a striking resemblance to the familiar aspect of motherese in humans, the researchers sum up.
Function similar to that of humans?
But what functions could this phenomenon have in bats? Possibly similar to humans, say Fernandez and Knörnschild. It is known that the sacred bats live in colonies with a complex social structure and communicate intensively with each other: In addition to their calls for echolocation when flying, they also emit many different communicative sounds that are learned in the course of childhood development.
Interestingly, there are already indications that, similar to humans, the training of social vocalizations in these bats is associated with a kind of “chattering”. As the two researchers report, their results show that the mother animals let their motherese-like vocalization sound while the young animals are busy practicing “babbling” vocalizations. “It is therefore conceivable that these young animal-directed vocalizations have a similar function to the motherese in small children: a general positive feedback for young animals during their Babbel exercises,” says Fernandez.
Source: Museum für Naturkunde – Leibniz Institute for Evolution and Biodiversity Research, specialist article: Front. Ecol. Evol., Doi: 10.3389 / fevo.2020.00265