Naked mole rats mimic the dialect of their colony’s queen

By Bethan Ackerley

Colonies of naked mole rats develop dialects in their vocalisations that may help them distinguish between friends and foes. These dialects are influenced by each colony’s queen, and become more varied if the queen dies.

Naked mole rats (Heterocephalus glaber) are extremely vocal creatures that live in colonies in which only one queen reproduces. To see whether their vocalisations help maintain their social structure, Alison Barker at the Max Delbrück Center for Molecular Medicine in Germany and her colleagues recorded more than 36,000 greeting calls, from 166 naked mole rats in seven colonies raised in labs in Germany and South Africa.

After identifying the acoustic features of these soft chirps, such as pitch, peak frequency and duration, the researchers used the calls to train a machine-learning algorithm. Not only could the algorithm reliably recognise individuals within a colony, but the chirps’ features were also highly predictive of which colony an animal belonged to, akin to human accents or dialects. This suggests that individuals from each colony have unique voices while all sharing the same dialect.

In another experiment, naked mole rats responded far more frequently to recordings of their own dialect than to other dialects, suggesting they use call and response when identifying colony members. The animals also responded to artificial chirps that shared the features of their dialect but were distinct from other colony members’ calls. “That shows that they respond to the general dialect,” says team member Gary Lewin.

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Barker and her team placed three abandoned pups in foster colonies and found that they all developed their adoptive homes’ dialect. The two younger pups replicated the new dialect entirely, but the slightly older one didn’t learn it as well, says Lewin.

“We did some preliminary analysis to test if every individual in the colony is trying to match the queen and surprisingly this did not seem to be the case,” says Barker. “We think it’s likely that hormonal cues may play a role.”

This may be the first time that cultural transmission of dialect has been seen in small rodents, says Barker. “There is some evidence in prairie dogs and in other species that there is transmission of different alarm calls, but in terms of a greeting call in rodents, I think this is the first.”

A colony’s queen also influences the naked mole rats’ dialect. During the study, one colony lost two queens. Chirps from the rest of the naked mole rats varied more during periods without a queen and became more similar again when a new queen was established. “You could almost say that the animals have the queen’s English,” says Lewin.

Journal reference: Science, DOI: 10.1126/science.abc6588

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