Scientists Say These Monkeys Use An 'Accent' To Communicate With Their Foe

May 29, 2021
Originally published on June 1, 2021 4:14 pm

In the Brazilian Amazon, a species of monkey called the pied tamarin is fighting for survival, threatened by habitat loss and urban development.

But the critically endangered primate faces another foe: the red-handed tamarin, a more resilient monkey that lives in the same region.

They compete for the same resources, and the red-handed tamarin's habitat range is expanding into that of the pied tamarins'. Their clashes sometimes end in violent altercations.

But in a recent study, scientists have discovered that the red-handed tamarin is altering its vocal calls to better communicate with the pied tamarin.

Tainara Sobroza, an ecology Ph.D. student who worked on the study, says these "territorial calls" are used to warn other species that they are encroaching on their territory, or coming too close to a crucial survival resource.

"When this happens, [the two species] usually engage in vocal battles," she says, which sometimes prevent the violent physical battles between the two species.

Researchers likened the change in calls to speaking with an accent.

"They might need to say 'tomahto' instead of 'tomayto' — that's the kind of nuance in the accent, so that they can really understand each other," Jacob Dunn, a professor of evolutionary biology who worked on the study, told The Guardian.

When analyzing the vocal call of both species, the scientists discovered that the red-handed tamarins new call has a narrower bandwidth and an increased amplitude, making the sound clearer and the duration of the call longer. The result is a call that travels better through the dense forest.

The hope is that this work will help conservationists to better design reserves and other survival mechanisms for the pied tamarins.

And because these two species are so rarely seen physically occupying the same space, listening is one way to do that work.

"We don't have to actually see," Sabroza says. "We can hear the ecological interaction."

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AUDIE CORNISH, HOST:

Communication is key, they say. And nowhere is that more true than in the Amazon, where thousands of animals fight for resources. In that crowded rainforest, the red-handed tamarin, a squirrel-sized monkey with brightly colored hands, relies on sound to mark its territory.

(SOUNDBITE OF RED-HANDED TAMARIN CALLING)

TAINARA SOBROZA: This is a territorial call. It's basically, this is mine.

MARY LOUISE KELLY, HOST:

Tainara Sobroza is a biologist at the National Institute of Amazonian Research in Brazil. She says in one corner of the Amazon, the red-handed tamarin competes with a similar species, the pied tamarin. And when they meet, it can spark vocal battles or worse.

SOBROZA: They call a lot. Sometimes, they even - they fight. And these can be very ugly fights.

CORNISH: But in studying these vocal battles, she and her colleague Pedro Pequeno have now discovered a curious phenomenon. Writing in the journal Behavioral Ecology and Sociobiology, they say the red-handed tamarins sometimes tweak the sound of their territorial battle cry to sound more like the pied tamarin's call. It's as if they're adopting an accent, Pequeno says.

PEDRO PEQUENO: There's a certain range of types of sounds they can produce, and they can modulate those sounds a little bit.

KELLY: Here's what the new call sounds like.

(SOUNDBITE OF RED-HANDED TAMARIN CALLING)

CORNISH: Might sound similar to our ears, but the researchers say adopting a common language of sorts may help the monkeys identify each other more easily and thus avoid conflict.

SOBROZA: If they sound the same, everybody will understand that that area is occupied.

KELLY: The pied tamarin is already critically endangered, imperiled by both the red-handed tamarin and the expansion of a nearby city. But scientists hope studying these monkey conflicts could help in the conservation of this disappearing tiny primate.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.