Researchers tracking grunts, whimpers and laughter across two geographically separated chimpanzee populations found that vocal differences sharpen with age. Their findings challenge the long-held assumption that the chimp calls are inflexible and determined solely by genetics.
Eastern chimpanzees (Pan troglodytes schweinfurthii), a mother with a young, at Gombe Stream National Park, Tanzania. Image credit: Ikiwaner.
“Dialects are a vocal signature of population membership,” said Queen Mary University of London doctoral researcher Kassandra Giragosian and her colleagues.
“Early in human ontogeny, vocal behavior is relatively similar across populations from an acoustic perspective.”
“As ontogeny progresses, the difference between populations becomes larger.”
“While research in recent decades has shown chimpanzees show population-specific vocal signatures, debates regarding the sources of this variation, namely whether it results from social, genetic, or ecological factors, continue.”
In the study, Giragosian and co-authors compared the vocalizations of infant and juvenile eastern chimpanzees (Pan troglodytes schweinfurthii) from two geographically separated populations.
One population was from Chimfunshi Wildlife Orphanage in Zambia and the other one from Gombe National Park in Tanzania.
By analyzing grunts, whimpers and laughter, the researchers discovered that differences between the groups became more pronounced as the animals grew older, suggesting that vocal behavior continues to develop throughout early life.
Analogously to people, who recognize different regional accents, they found that young chimpanzees from different communities produced subtly different vocal patterns too.
Moreover, some population-specific vocal characteristics were already present in infancy, while others emerged during the juvenile years.
This developmental pattern suggests that social interactions, environmental conditions and other non-genetic influences may all contribute to shaping how young chimpanzees communicate.
The findings provide the first evidence that population-specific vocal differences become increasingly distinct during chimpanzee development.
By focusing on how communication changes over time, rather than simply comparing adults from different populations, the research offers a new perspective on the processes that shape vocal behavior in other species.
“Understanding how communication develops during early life is fundamental to understanding animal behavior,” Giragosian said.
