A chimpanzee mother and offspring of the Kanyawara community. Credit: Ray Donovan (CC-BY 4.0, https://creativecommons.org/licenses/by/4.0/)
Research conducted by the University of Zurich has found that young chimpanzees pick up most of their communication style from their mother and maternal relatives, rather than their father.
The results suggest that the social learning of communication is not unique to humans and dates the behaviour back further on the evolutionary tree than previously thought.
Like humans, chimpanzees communicate using vocal signals and facial expressions. Until now scientists were still unclear as to whether these behaviours are genetically inherited or learnt in chimps.
To investigate this, researchers observed the behaviour of 22 wild chimpanzees from the Kanyawara community across Kibale National Park, Uganda.
This community of wild chimpanzees has been the subject of a long-term study which has observed their health, reproduction and welfare since 1987.
While the research team recorded the vocal signals of the chimpanzee, they also observed non-verbal communication forms like body postures, eye contact and arm moments. The data was collected between June 2014 and March 2015.
“In humans, body language includes hand gestures and facial expressions, but also many subtle behaviours, like shifts in posture and gaze direction,” says co-author Simon Townsend, a professor at the University of Zurich, Switzerland.
“With our approach, we were able to assess whether chimpanzees learn about these less salient features as well.”
A chimpanzee mother vocalizes while her offspring looks on, in Kibale National Park, Uganda. Credit: Ray Donovan (CC-BY 4.0, https://creativecommons.org/licenses/by/4.0/)
The team observed a strong correlation between how a chimpanzee communicated and how their mothers and maternal relatives did. For example, chimpanzee mothers who used a greater number of vocal-visual combinations raised offspring who also communicated with in this way.
“What we see is that certain chimpanzee mothers tend to produce many vocal-visual combinations, while others produce few. And the offspring end up behaving like the mothers, resulting in family-specific tendencies,” says Joseph Mine, co-author of the study from the department of evolutionary anthropology at Switzerland’s University of Zurich.
“I think it’s fascinating that mothers who produce more visual behaviours when they vocalise, raise offspring that follow suit,” says co-author Katie Slocombe, a professor at the University of York, UK.
Chimpanzee mothers are the main caregivers, while fathers do not contribute to parenting. The results suggest that since chimpanzees are around their mother more, their communication style may involve a learned component rather than a genetic one.
The chimpanzees were over the age of 10, which is the age when the species starts to detach from their mothers and become more independent. The findings indicate that a chimpanzee mother has a continuing impact on the behaviour of her adult children.
“The next exciting step will be to see if offspring are learning certain types of visual-vocal combinations from their mothers, in addition to the number of visual behaviours they produce when they vocalise,” says Slocombe.