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January 28, 2021
from the Max Delbrück Center for Molecular Medicine
Some people converse in Creole while others speak Scots, but it’s not just people who can be identified by the variety of languages they speak. Naked mole rats also have their own dialects. A common dialect also strengthens cohesion within a colony, reports a team led by MDC researcher Gary Lewin in Science.
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Naked mole rats are very communicative creatures. When you stand in front of their house and listen, you can hear the little rodents chirp, squeak, chirp or even grunt softly. « We wanted to find out whether these vocalizations have a social function for the animals that live together in an orderly colony with a strict division of labor, » says Professor Gary Lewin, head of the Laboratory for Molecular Physiology of Somatic Sensation at the Max Delbrück Center for Molecular Medicine Helmholtz Association (MDC).
Lewin worked with Dr. Alison Barker from his own team and other researchers at the MDC and the University of Pretoria in South Africa – Professor Nigel Bennett and Dr. Daniel Hart – together to analyze the twittering with which the naked mole rats greet each other. « We found that each colony has its own dialect, » says Barker, lead author of the study published in Science. « The development of a common dialect strengthens the cohesion and the feeling of belonging to the naked mole rats of a particular colony. »
Foreigners are not welcome in an established naked mole rat colony. « You could even say that these animals are extreme xenophobes, » says Lewin, who has been studying naked mole rats at the MDC for around 20 years. « This behavior is probably due to the permanent lack of food in the dry plains of the East African habitat of the naked mole-rat. In their own colony, however, the rodents work harmoniously together. Everyone knows his rank and the tasks he has to perform – and usually perform reliably.
In order to analyze the language of the naked mole rats, Lewin’s team recorded a total of 36,190 chirps from 166 people from seven colonies of naked mole rats that were kept in laboratories in Berlin and Pretoria over a period of two years Lewin and Barker’s colleague, the mathematician Grigorii Veviurko, who now works at the Technical University of Delft in the Netherlands, used an algorithm to analyze the acoustic properties of each vocalization. « This enabled us to identify eight different factors such as height or degree the asymmetry in the sound spectrogram grasp and compare, « explains Lewin.
Veviurko also developed a computer program that, after an initial training phase, was able to detect very reliably which twittering came from which individual naked mole-rat. « So then we knew that every naked mole-rat has its own voice, » says Barker. « What we didn’t know, however, was whether the animals could recognize each other by their voices. »
The computer program that uses AI not only identified the animals by their individual voices: « There were also similarities between the types of Detected noises that were generated within a single colony, « says Lewin. The program was therefore also able to identify which colony a particular person came from. « That meant that each colony likely had its own dialect, » says Barker. At this point, however, the research team did not yet know whether the animals were aware of this and whether they could recognize their own dialect and distinguish it from others.
To find out these two things, Barker carried out several experiments. In the first, she repeatedly placed a naked mole-rat in two chambers connected by a pipe. Another naked mole rat chirping could be heard in one chamber, while the other chamber was silent. « We found that the animals always immediately went into the chamber where the chirping could be heard, » says Barker. If the noises were made by a person from the subject’s own colony, this would give an instant voice response, but if made by a person from a foreign colony, the mole rat would be silent. « This enabled us to conclude that naked mole rats can recognize their own dialect and will react selectively to it. »
To ensure that the test subjects responded to the dialect and not to the voice of someone they knew, the researchers intentionally created artificial ones Sounds. These contained features of every dialect but did not resemble the voice of any particular person. « The naked mole rats reacted loudly to the chirping developed by the computer, » reports Barker. And the experiment worked even when the chamber in which the familiar and trustworthy dialect was heard received the scent of a strange colony. « This showed that the naked mole rats reacted more to dialect than to smell and reacted positively to hearing their own dialect, » says Lewin.
In further experiments, the researchers placed three orphaned naked mole rat pups in foreign colonies where the queen – the only female in bare mole rat colonies who breeds – also recently had a litter. « This ensured that the newcomers were not attacked, » explains Barker. « Six months later, our computer program showed that the foster pups had acquired the dialect of their new home. »
It was more or less by chance that the team discovered another interesting fact: a naked queen mole is not just for breeding in her colony responsible, but also plays a vital role in controlling and maintaining dialect integrity. « In the course of the study, one of our colonies lost two queens within a relatively short period of time, » says Lewin. « In the anarchy that followed, we observed that the vocal utterances of the other nude mole-rats in the colony began to vary much more than usual. Dialect cohesiveness was therefore greatly reduced and did not return until a few months later with the rise of another high-ranking woman as the new queen . «
» Humans and naked mole rats seem to have much more in common than anyone would have thought before, « concludes Lewin. « Naked mole rats have a language culture that evolved long before humans existed. The next step is to find out what mechanisms in the animal’s brains support that culture, as this could give us important insights into how human culture evolved. »
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Ref: https://phys.org
