Young chimpanzees develop distinct regional call patterns as they grow
A team led by Kassandra Giragosian at Queen Mary University of London studied 30 infant and juvenile chimpanzees from two separated populations and found their grunts, whimpers and laughter grew more population-specific with age. Juveniles showed the pattern in all three calls, but infants only in their laughs and grunts. Nautilus reports the team traced this to the whimper's alarm function and compared it with human vocal development, where laughter varies more across languages than distress calls.
Science··Night
Juvenile chimpanzees' calls diverge by population in all three sound types
A team led by Kassandra Giragosian at Queen Mary University of London, working with the University of Portsmouth, studied 30 infant and juvenile chimpanzees from two geographically separated populations, comparing the acoustic structure of their grunts, whimpers and laughter. Juvenile chimpanzees' grunts, whimpers and laughs all varied subtly with population, while infants showed the same population-specific pattern only in their laughs and grunts; their whimpers stayed similar across populations. Some of the differences between the two groups are already present in infancy and others appear only during the juvenile years, so the acoustic distance between the populations widens as the animals grow. The study is published in the journal PLOS One.[1], [2]
Nautilus ties the pattern to the whimper's alarm function and to human vocal research
Nautilus reported the team's explanation for why the whimper lags behind: laughter and grunts are more speech-like calls, while the more constrained whimper serves an alarm function that alerts mothers to a baby chimpanzee's location when it is out of sight, which may be why it changes least with age. The magazine noted that the pattern echoes earlier human research: laughter, a call tied to positive emotion, varies more across human languages than negatively toned calls such as screaming or crying, and cited a 2009 study finding that French infants cry with a rising melody while German infants' cries follow a falling one, a difference researchers trace to accents that begin developing in the womb. Nautilus also cited a 2015 study of two chimpanzee troops that were brought together, whose distinct grunts blended and converged as the troops merged, evidence that these calls can keep changing well into adulthood.[2]
Giragosian says the calls keep developing rather than staying fixed from birth
Giragosian said the calls keep developing as young chimpanzees interact with their social and ecological surroundings, rather than staying fixed as they were at birth. The team said social interactions, environmental conditions and other non-genetic influences may all contribute to the pattern, so the finding shows an association between age, population and call structure, without pinning down what drives it.[1]
