Monkeys will use the “accent” of another species when they enter its territory to enhance communication, much like a British person living in the US might forgo their ‘tomahto’ for ‘tomayto, researchers have found.
Researchers investigated the behaviour of 15 groups of two roughly squirrel-sized primate species in the Brazilian Amazon: pied tamarins (Saguinus bicolor) and red-handed tamarins (Saguinus midas).
The critically endangered pied tamarin – a species with a black hairless face, white shaggy fur on the neck and shoulders and an almond-hued coat from the waist down – largely live around the city of Manaus. Red-handed tamarins, which have ginger hands and feet and a body covered in black fur, are found across the north-east Amazon region.
Unlike humans, other primates do not use a variety of languages. Instead, they have a fixed number of “calls” within their vocal repertoire that encompass a variety of contexts, such as predator warnings and mating propositions. They cannot learn new calls, said the study’s author, Dr Jacob Dunn, an associate professor in evolutionary biology at Anglia Ruskin University.
By comparing recordings of the acoustic profile or calls of the two species in three locations – places inhabited solely by pied tamarins; by red-handed tamarins; and areas inhabited by both species – the researchers found that the red-handed tamarins adopted the calls of their neighbours in the shared region, according to the study published in the Behavioural Ecology and Sociobiology journal.
“The red-handed tamarin call becomes much more like the pied tamarin’s – and we think that the reason they do this is because when you’re in this shared area and you’re a closely related species, you’re very likely to come into competition over resources, because you’ve got a similar diet and habitat requirements,” said Dunn.
“You need a call that can be understood by this other species so that you can regulate territorial disputes.”
The two species practically speak the same language anyway, but they need to understand each other’s accents, he added.
“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’.”
Why the red-handed tamarins were more adaptive – versus the pied tamarins, which seemingly did not try to meet their comrades in the middle – remains a mystery and is the subject of ongoing research, he added.
But since red-handed tamarins tend to be relatively more vocally territorial, Dunn speculated, it could be the species might be predisposed to make the change.