Amazon monkeys change their tone of voice and “speak” differently when interacting with another species – 6/29/2021 – Science

A species of monkey living in the Amazon, the goldenhand tamarin (Saguinus midas), can change the sound of its screams when it shares with another species of primate, the tamarin-de-coleira (Saguinus bicolor). In practice, it is as if the tamarin with golden hands spoke differently, more accessible to other common marmosets.

The behavior was described by researchers from institutions in Brazil and abroad in an article published in May in the journal Behavioral Ecology and Sociobiology.

Species that normally interact a lot in the same environment may change their characteristics to become more similar to the other group of animals as a result of coexistence, but this is the first record of a change in type in a primate’s cries.

“Their noises are the same in the areas they share. That may mean that they do not recognize one species or the other through noise, but rather the behavioral context in which this noise is emitted,” says Tainara Sobroza, biologist at the National Institute for Research in the Amazon (Inpa) and the Sauim-de-Coelira-Projekt (Ufam) and one of the authors of the article. “It’s like they’re talking: this is mine.”

The tamarin with golden hands creates a different sound in other rooms that are not shared with other common marmosets. The rat monkey makes the same noises in every forest, whether it is shared with other species or not.

According to Sobroza, this shows that the tamarin is more flexible and can adapt better to different locations – so much so that the species occupies a much larger area than the tamarin, which only lives in the region, of two other cities near the capital of the Amazon.

Scientists have collected audios from 15 groups of species that have been found over several years. The sounds were examined in a computer program that analyzed various parameters of the sound emitted by the species.

“We usually think of sound as a thing, but actually primate language has one main energy that comes out of the lungs, and that wave goes through the vocal cords, nose, tongue, teeth … There are many filters in the voice apparatus,” says Sobroza.

In the goldhand tamarin, the tone that is produced in the vicinity of the other species has a narrower range. “You can make louder noises in a more restricted frequency range; it is a sound that spreads better in the forest and lasts a little longer,” says the biologist.

Sobroza and colleagues who conducted the research believe primates altered the sound of screams to save animals from the cost of competition. Since the 1980s, studies have suggested that these two species may compete for space and food.

These territorial sounds, used to defend an area, are used to prevent groups from crossing over and starting a fight – which, according to the scientist, is usually very violent.

According to Sobroza, research into these species is more important than ever for conservation planning as the tamarin is critically endangered and has a disadvantage in interacting with the adaptable tamarin.

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