Brazil's Amazon Rainforest is home to various genera of tamarin monkeys. Tamarins are a group of diverse squirrel-sized primates that dwell in the forest's dense canopy. New research has shown that, if they live in proximity to one another, red-handed tamarins (Saguinus midas) may mimic pied tamarins’ (Saguinus bicolor) calls in order to communicate and avoid conflict. The study, published this month in Behavioral Ecology and Sociobiology, is the first to show primates adapting to another species’ call pattern when entering new territories.
Red-handed tamarins, also known as Midas tamarins, are a resilient species that can adapt and survive near villages and on forest edges. In contrast, pied tamarins are critically endangered and have one of the smallest ranges of any primate group worldwide, reports Sara Rigby for BBC Science Focus. Pied tamarins may also face threats of being outcompeted by red-handed tamarins expanding into their habitat.
In their dense forest domains, tamarins use high-pitched calls to alert other primates of their presence and to discourage them from getting too close, reports Clare Wilson for New Scientist. Red-handed tamarins have greater vocal flexibility, using calls ranging from territorial long calls to chirps to trills to communicate, whereas pied tamarins use long whistle-like calls, reports Zamira Rahim for CNN.
Researchers observed 15 groups of pied tamarins and red-handed tamarins in three different locations within the rainforest. The team recorded long calls in areas inhabited by only pied tamarins and areas inhabited solely by red-handed tamarins in the first and second locations. In the third location, they recorded areas where the primates co-existed. When comparing recordings from the various locations, the biologists found that the red-handed tamarins were changing and adapting their calls to sound like the pied tamarin's calls in the shared regions, the Guardian's Natalie Grover reports
“We found that only the red-handed tamarins change their calls to those of the pied tamarins, and this only happens in places where they occur together,” said ecologist and first author Tainara Sobroza in a statement.
Both primate species are closely related, and have similar diets and habitat requirements. So, the red-handed tamarin adapting its calls to sound more like a pied tamarin call may help the primates identify one another more efficiently, settle territorial disputes and avoid conflict, explained Jacob Dunn, co-author and expert in evolutionary biology at Anglia Ruskin University, in the statement.
“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. And so they're kind of playing around within the constraints … they can make the call longer or slightly higher or lower frequency, or a bit harsher or a bit more tonal. They can sort of change the noise a bit, but essentially, they're still saying the same 'words,'” Dunn explained to the Guardian.
The behavior was only observed in red-handed tamarins, and while researchers do not know why the primates were more adaptive in their calls, they suspect it may have to do with their tendency to be more vocally territorial, per the Guardian.
“Why their calls converge in this way is not certain, but it is possibly to help with identification when defending territory or competing over resources,” commented Sobroza in the statement.