Marmosets Use Names to Call Each Other, Study Finds

Marmosets may be small, endearing monkeys from South America, yet they should not be underestimated. These tiny primates lead intricate social lives in troops high in the forest canopy.

Marmosets use names in their treetop troops

A new study suggests that marmoset troop members call one another by name. Until now, this behaviour had been recorded in only three notably intelligent animals: elephants, dolphins and humans. Parrots, however, have also been shown to develop individual vocal signatures that identify themselves.

The study’s authors report that marmosets rely on particular vocalisations, called "phee calls", both to identify one another and to communicate.

A naming system is a significant finding in any species, given the small number of wild animals known to possess one. Its discovery in another primate is particularly noteworthy: previously, humans were the only primates known to identify each other by name.

Among primates, this capacity has now been identified in monkeys that are distantly related to us, rather than in closer relatives such as great apes.

As well as revealing more about these far-removed relatives, the researchers say the results could improve our understanding of how language emerged in our own ancestors.

How the researchers studied phee calls

To investigate the secrets of marmosets, the team recorded natural exchanges between pairs of primates that could hear, but not see, each other. They also recorded interactions between a marmoset and a computer.

The scientists focused on phee calls, a known form of contact call that they suspected could have additional functions that had not yet been recognised.

Marmosets already use phee calls to create turn-taking conversations, the researchers note. These calls can also reportedly carry information about the individual making them.

Because phee calls are both distinctive and flexible, the team proposed that marmosets might use them to label one another during natural phee-call exchanges. Such labels could form part of a wider naming system, potentially learned socially within troops.

Led by David Omer, an assistant professor at the Safra Center for Brain Sciences at the Hebrew University of Jerusalem, the researchers found that marmosets do use distinctive phee calls to assign vocal labels to each other.

The study also showed that the monkeys accurately recognised and responded to phee calls aimed at them.

"This discovery highlights the complexity of social communication among marmosets," Omer says. "These calls are not just used for self-localization, as previously thought – marmosets use these specific calls to label and address specific individuals."

Social learning and vocal labels

According to the findings, troop members use individual vocal labels when addressing each monkey and repeatedly employ particular sound features to encode specific names. This appears to mirror elements of human speech, including vocal labels functioning as names and the presence of localised dialects.

The researchers report that social learning probably makes every individual’s name widely known within a troop, rather than this occurring only among young monkeys or close relatives.

Even adult marmosets with no family connection can learn one another’s names and pronunciation features in this manner, the study found. This indicates that wild troop members learn both names and dialects from their companions.

Marmosets live in dense rainforest canopies across part of South America, where giving each troop member a vocal label may provide an adaptive benefit, the researchers note.

Although visibility is poor among the thick treetops, names expressed through vocal labels could help the monkeys sustain social relationships and preserve group cohesion while they spend substantial periods out of one another’s sight.

This may even offer a clue to the way some prehuman ancestors developed social communication and language.

"Marmosets live in small monogamous family groups and take care of their young together, much like humans do," Omer says. "These similarities suggest that they faced comparable evolutionary social challenges to our early pre-linguistic ancestors, which might have led them to develop similar communicating methods."

The study was published in Science.