Naked mole-rats ‘speak’ in different ‘languages’ just like humans, study shows

BERLIN — Naked mole-rats are among the most unique rodents to walk the Earth, with mysteriously long lifespans that have long been studied by scientists. Now, researchers are adding language to the list of their impressive characteristics. A new study shows that these bizarre-looking also have different dialects just like humans.

Scientists say that naked mole-rats chirp, squeak, twitter or even grunt to one another, with the variety of sounds unique to each community.

Co author Professor  said: “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,” explains co-author Gary Lewin, head of the Molecular Physiology of Somatic Sensation Lab at the Max Delbrueck Center for Molecular Medicine. “If you stand outside their home and listen, you can hear the little rodents quietly ‘chatting.'”

Naked mole-rats are eusocial animals. Within their colonies there is a strict hierarchy which affects how the rodents overtake each other in their tunnels. They also chirp constantly – for example to greet each other. (Photo credit: Colin Lewin)

Naked mole-rats live in hostile desert regions underground and have to work together to get their food. The challenging lifestyle has made them one of the most communicative creatures in the world.

So the Berlin-based research team analyzed the noises they use to greet one another.

“In so doing, we established each colony has its own dialect,” says lead author Dr. Alison Barker. “The development of a shared dialect strengthens cohesion and a sense of belonging among the naked mole-rats of a specific colony.”

The authors also learned that foreigners are not welcome in an established naked mole-rat colony. “You might even say these animals are extreme xenophobes,” says professor Lewin, who has studied the naked mole-rat for about 20 years. “This behavior is probably a result of the permanent shortage of food in the dry plains of its East African habitat. Within their own colony, however, the rodents work together harmoniously. Each one knows its rank and the tasks it has to perform – and usually accomplishes them reliably.”

The bizarre lives of naked mole-rats

Over millions of years, the wrinkly, hairless critters have cast off things which uses their energy and isn’t necessary to survive. This includes their fur, but also results in surprising abilities. For instance, it uses its distinctive, elastic “baggy” skin, to squeeze through tunnels. The study published in Science sheds fresh light on human evolution, and the basic workings of culture.

It was previously thought that only people could be identified by the diversity of the language they speak. “Human beings and naked mole-rats seem to have much more in common that anyone might have previously thought,” says Lewin. “Naked mole-rats have a linguistic culture that developed long before human beings even existed.”

Over two years the researchers recorded a total of 36,190 chirps made by 166 individuals from seven colonies held in laboratories in Berlin and Pretoria. An algorithm worked out the acoustic properties. “That enabled us to collect and compare eight different factors such as the height or level of asymmetry in the sound spectrogram,” explains Lewin.

A computer program, after an initial training period, was then able to very reliably detect which noise came from which animal.

“So then we knew that each naked mole-rat has its own voice. What we didn’t know, however, was whether the animals could recognize one another from their voices,” says Barker.

Over millions of years, naked mole-rats have cast away everything underground which uses their energy and isn’t necessary to survive. This includes their fur – but also results in surprising abilities. (Credit: Felix Petermann, MDC)

The artificial intelligence technique also recognized similarities in the types of sounds made within a single colony, even identifying which colony a specific individual came from. “That meant that each colony probably had its own distinct dialect,” says Barker.

In experiments where naked mole rats were placed in chambers connected by a tube, they recognized their own and distinguished it from others.

“We observed the animals always immediately headed for the chamber where the chirps could be heard,” Barker adds.

If the sounds were made by an individual from the test subject’s own colony, it would give an immediate vocal response. But if they were made by an individual from a foreign colony, the mole-rat would remain silent.

“That enabled us to infer naked mole-rats can recognize their own dialect and will selectively respond to that,” says Barker.

The queen determines dialect

In further tests, three orphaned naked mole-rat pups were placed in foreign colonies where the queen – the only female that reproduces – had also recently had a litter. “That ensured the new arrivals would not be attacked. Six months later, our computer program showed the foster pups had acquired the dialect of their new home,” says Barker.

The study also found the queen plays a decisive role in controlling and preserving dialect integrity. “One of our colonies lost two queens within relatively quick succession,” says Lewin. “In the anarchy that ensued, we observed the vocalizations of the other naked mole-rats began to vary much more widely than usual. Dialect cohesiveness was thus greatly reduced and did not return until a few months later, with the ascendance of another high-ranking female as the new queen.”

Lewin adds: “The next step is to find out what mechanisms in the animals’ brains support this culture, because that could give us important insight into how human culture evolved.”

The slightly unsightly creature has fascinated medical experts for decades. It is cancer resistant, with a lifespan of 30 years — by far the longest for a rodent. It also has the lowest metabolic rate of any mammal, and an incredible tolerance to pain.

“Evolution has shut down everything that is not absolutely necessary – including extra nerve receptors,” says Lewin.

Doctors believe the humble naked mole-rat holds the key to combating a host of diseases.

SWNS writer Mark Waghorn contributed to this report.