Science: Gorillas speak like perfect democrats

The great apes never cease to amaze us. Did you know, for example, that before moving in a group, gorillas carry out a sort of “vote”? And the strongest in the group doesn’t necessarily have the last word? We owe this recent discovery to a research team from the University of Neuchâtel and the National Museum of Natural History in Paris, which traveled to the Central African Republic.

A student for two years in Neuchâtel and first author of the study, Lara Nellissen was part of the expedition. Accompanied by trackers, aka hunter-gatherers, for eleven months she observed three groups of western gorillas, who live in the forest of the Dzanga-Sangha protected areas. “We monitored the focal animals, that is to say we focused on a different individual each day and throughout the day,” explains the young researcher.

The role of the “silverback”

To better understand how these hominids interact, you should know that they live in family groups, made up of a single adult male silverback, surrounded by females and their offspring. Twice the size of the females, the “silverback” plays the role of leader and everyone relies on him to protect them against other “silverbacks” not related to the group.

Western gorillas move very frequently in search of food, especially fruits. But each member of a group may have different information and needs. So who gives the starting signal, and to go where?

“For gorillas, it is crucial to maintain group cohesion,” explains Lara Nellissen. Thus, we noticed that to move, these animals vocalize before departure to ensure that everyone agrees. And despite its dominant position, the powerful “silverback” is not the only one speaking out!

Quorum wins

The choice of a new destination is indeed a very democratic process. In the five minutes before the group leaves, the vocal activity of the great apes increases considerably. Nearly half of the cries, which sound like growls, are part of exchanges with other members of the group.

“We also found that the gorillas were more inclined to leave if a high number of members of the group had vocalized,” indicates the UNINE student. This suggests that gorillas may respond to a form of quorum: once a threshold number of individuals have decided in favor of a behavior, the entire group adopts it.

This quorum phenomenon has already been described in other species, such as meerkats and wild dogs.

Convince the group

For scientists, these observations show that the “silverback” is not the only individual to decide when to leave. His consent is not even necessary! On the contrary, each member of the group can influence the others.

Well, not necessarily all. “Young gorillas can also emit cries, but much less frequently than adult individuals,” explains Lara Nellissen. So they most likely play a minor role in the decision-making process.”

The UNINE student further notes that “if individuals start to move but are not followed, they stop, look at the other members of the group and vocalize until others follow. But this doesn’t always work and the individual is left with no choice but to sit back and wait for someone else to start moving.”

Recognize voices

Observing the “speech” of these great apes is not necessarily easy, underlines Lara Nellissen, “even if those with whom I worked are accustomed to human presence, via the WWF Central African Republic habituation program. . It is important to keep enough distance and be careful not to block their path. We must behave in such a way that the gorillas forget your presence.”

It was also essential for her to recognize each individual by their voice. “For this, I was able to count on the aka trackers. Thanks to them, after a few weeks of observations, I too began to identify differences in the gorillas’ voices!”

Lara Nellissen also benefited from the great knowledge of her supervisor Shelly Masi, lecturer at the Museum and who has studied gorillas for more than twenty years, as well as the help of her UNINE professor, Klaus Zuberbühler, specialist in animal communication and more particularly in primates.

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Xavier Lafargue has been a professional journalist since 1985. After fifteen years spent in sports sections, he opted for local news. He has worked since 2008 in the Geneva section of the Tribune de Genève, a section which he headed for six years before returning to writing.More info

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