Naked Mole-Rats Speak in Community Dialects

Fascinating creatures that captivate scientists with their habits and adaptations, naked mole-rats are pink, nearly hairless rodents that live underground in large colonies. They’re extremely social and very vocal as they communicate within their group. And now researchers have found that when they talk, they speak in dialect.

Sharing a dialect strengthens cohesiveness in the colony, scientists report in a new study in the journal Science.

When naked mole-rats communicate, they talk in chirps, squeaks, twitters, and even grunts. Earlier studies have found that the animals have at least 17 different calls and they vocalize almost continuously.

"We wanted to find out whether these vocalizations have a social function for the animals, who live together in an ordered colony with a strict division of labor," says Professor Gary Lewin, head of the Molecular Physiology of Somatic Sensation Lab at the Max Delbrueck Center for Molecular Medicine in the Helmholtz Association in Berlin.

Over a two-year period, Lewin and his team recorded 36,190 chirps made by 166 animals from seven naked mole-rat colonies in Berlin and Pretoria. They used an algorithm to analyze the acoustic properties of the vocalizations. Then they developed a computer program that was able to recognize the individual animals by voice, and then the similar sounds within each colony.

They suspected that the animals probably had their own dialect within each colony. To find out for sure, co-corresponding author Alison Barker, PhD, led several experiments. In one, she would place a naked mole-rat in two chambers connected by a tube. In one chamber, a chirping mole-rat could be heard, while the other chamber was silent. When the mole-rat was from the same colony as the one that could be heard, the animal would chirp in return. If it was from a different colony, the mole-rat would remain silent. 

To make sure they weren’t responding just to a known individual, researchers also created artificial sounds with the exact characteristics of the familiar dialect. The naked mole-rats responded to the computer sounds just like they did to recordings of the real animals.

Friends vs. Strangers

The researchers believe that the dialect helps with group solidarity and connection.

“We think that one reason naked mole-rats use vocal dialects is for social cohesion. This is similar to the role dialects play in human societies,” Barker tells Treehugger.

“In any social group, including our own, having a rapid way of identifying who belongs to the group and who is excluded is useful for many practical reasons, such as sharing food and other resources or in defending the colony’s territory. It is likely that dialect use is one of the many ways in which naked mole-rats employ vocal cues to organize their societies and that their development of a large vocal repertoire, in comparison to other rodents, may be one crucial key to their extraordinary cooperation.”

Having a familiar dialect also plays an important role in recognizing friend or foe. Naked mole-rats are very wary of strangers.

“In the wild, food resources are limited and closely shared among colony members. For this reason, newcomers are often greeted aggressively. It is likely that one method for recognizing non-members is through differences in vocal greetings,” Barker says.

“Interestingly, young mole-rats that were fostered into foreign colonies were able to learn the dialect of the new colony and were successfully integrated, suggesting that peaceful entry into new colonies is possible when the correct dialect is learned.”

Young pups learn the dialect as they are growing up. And the dialect, researchers believe, is strictly maintained by the mole-rat queen — the only breeding female in the colony. 

“When the queen is lost, much of the colony organization is also lost. Remarkably, this loss of structure is also observed in the colony dialect: individuals increase their vocal variability and the overall cohesiveness of the dialect disintegrates,” Barker says.

“We are still unsure precisely how the queen preserves dialect integrity, but it’s a fascinating question for future study.”