https://www.sciencealert.com/thousands-of-recordings-of-chimpanzees-reveal-a-hidden-language-we-never-knew-aboutWhile call combinations of chimpanzees have been studied before, until now the sequences that make up their whole vocal repertoire had never been subjected to a broad quantitative analysis.
To rectify this, the team captured 900 hours of vocal recordings made by 46 wild mature western chimpanzees (Pan troglodytes verus), belonging to three different chimp communities in Taï National Park.
In analyzing the vocalizations, the researchers identified how vocal calls could be uttered singularly, combined in two-unit sequences (bigrams), or three-unit sequences (trigrams). They also mapped networks of how these utterances were combined, as well as examining how different kinds of frequent vocalizations were ordered and recombined (for example, bigrams within trigrams).
In total, 12 different call types were identified (including grunts, pants, hoos, barks, screams, and whimpers, among others), which appeared to mean different things, depending on how they were used, but also upon the context in which the communication took place.
"Single grunts, for example, are predominantly emitted at food, whereas panted grunts are predominantly emitted as a submissive greeting vocalization," the researchers explain in their paper, led by co-first authors Cédric Girard-Buttoz and Emiliano Zaccarella. "Single hoos are emitted to threats, but panted hoos are used in inter-party communication."
In total, the researchers found these different kinds of calls could be combined in various ways to make up 390 different kinds of sequences, which they say may actually be an underestimation, given new vocalization sequences were still being found as the researchers hit their limit of field recordings.
