Once again the famous Nackedei rodents live up to their bizarre reputation: In order to convey their ethnicity, the state-building naked mole rats squeak with accents, shows a study. The phenomenon is thus similar to dialects in human languages, say the researchers. Interestingly, as they report, the queen of a colony also plays a role in the “linguistic” development of a naked mole rat.
They don’t look pretty to us, but from a scientific point of view, the naked mole rat (Heterocephalus glaber) fascinating, because they have a number of spectacular features. The central peculiarity is: These rodents form states similar to social insects. They live in huge underground structures in the semi-deserts of East Africa. The up to 300 animals are organized in a complex system with a strict division of labor. They are dominated by a queen who alone produces the offspring. Another feature of interest for research is the unusually long life span for rodents: naked mole rats can live up to 30 years. However, they do not develop cancer and other peculiarities make them very exciting from a medical point of view. That is why naked mole-rats are kept and researched in various laboratories around the world.
Communicative nudity
The scientists led by Gary Lewin from the Max Delbrück Center for Molecular Medicine in Berlin have now devoted themselves to an aspect that has hardly been investigated before: Naked mole rats are very communicative living beings. The little rodents make many different sounds – from squeaking to grunting. “We wanted to find out what social functions these sounds have for the animals,” says Lewin. In principle, it was already clear in this context: “You could say that Nackmulle are extremely xenophobic,” said Lewin. Animals from other colonies are attacked immediately and even killed. However, they work together harmoniously within their own people: everyone knows their rank and the tasks they have to fulfill.
To analyze the “language” of the naked mole rat, the scientists recorded a total of 36,190 voices from 166 individuals from seven naked mole rats over a period of two years, which are kept in laboratories in Berlin and at the University of Pretoria in South Africa. Special software for acoustic analysis was used to analyze the sounds. “This enabled us to record and compare eight different factors such as the height or the degree of asymmetry in the sound spectrogram,” explains Lewin.
Another computer program based on artificial intelligence was able to make it clear that every naked mole rat has an individual sound signature. But not only that: “The analysis process also recognized similarities in the characteristics of the sounds that were generated within an individual colony,” says Lewin. Accordingly, the program could also assign the people from which a certain individual comes. “That means: each colony apparently has its own specific dialect,” says co-author Alison Barker.
Recognized by the dialect
In subsequent experiments, the researchers investigated what role this could play for the animals. They investigated how the naked mole rat react to strange or familiar calls. “We observed that laboratory animals in our test system always immediately went to a chamber from which the sounds of a familiar conspecific could be heard,” says Barker. If the noises were generated by an individual from their own colony, the test animals also immediately gave a voice response. However, if an individual from a foreign colony was heard, the test animal remained silent. “From this we were able to deduce that naked mole rats can recognize their own dialect and react selectively to it,” says Barker.
To ensure that the test animals responded to the dialect and not to the voice of a familiar conspecific, the researchers created artificial sounds. These contained characteristics of the respective dialect, but did not resemble the voice of a particular animal. “The naked mole rats reacted positively to this computer-developed voice,” reports Barker. They were drawn to her even when the researchers smelled a strange colony. “This showed that the naked mole rat react specifically to the dialect and not to the smell and that they have a positive reaction to hearing their own dialect,” concludes Lewin. Through further experiments, the scientists were also able to show that the naked mole rat learn the dialect as babies. To do this, they moved naked mole rat pups from one colony to another, where they were adopted. “Six months later, our computer program showed that the foster children had acquired the dialect of their strange home,” reports Baker.
The queen shapes the language
The team also discovered that the dialect has something to do with the queen of a colony: she therefore plays a crucial role in controlling and maintaining this sign of group belonging. “In the course of the study, one of our colonies lost two queens one after the other within a relatively short period of time,” says Lewin. “In the respective phases without a head, we observed that the vocalizations of the naked mole rat in the colony began to vary much more than before. The dialectal cohesion was greatly reduced and only returned a few months later when a new female rose to be the new queen, ”reports Lewin.
He and his colleagues now want to further research the basics of the “linguistic culture” of these fascinating rodents. “The next step is to find out which mechanisms in the animal’s brain support these abilities,” says Lewin. According to him, this could even shed light on principles in humans. “Humans and naked mole rats seem to have a lot more in common than was previously thought,” says the scientist.
Source: Max Delbrück Center for Molecular Medicine, specialist article: Science, doi: 10.1126 / science.abc6588