Call combination order and iterations may shift meaning in sooty mangabey vocal sequences

Area of Science:

• Primate communication
• Animal vocalizations
• Evolution of language

Background:

• Human language relies on combining sounds for meaning, a rare trait in nonhuman animals.
• Meaningful call combinations are documented in apes but mainly in alarm contexts in other species.
• The evolution of combinatorial communication in animals remains largely unexplored.

Purpose of the Study:

• To investigate meaningful combinatorial vocal communication in sooty mangabeys (Cercocebus atys).
• To assess if sooty mangabeys use call sequences to convey context-specific meanings.
• To explore the role of call bigrams and iterations in primate communication.

Main Methods:

• Recorded 1751 vocal utterances from two sooty mangabey groups.
• Analyzed call sequences, specifically bigrams (two different calls) and iterations (recurrent calls).
• Used context of production as a proxy for meaning and Euclidean distance analyses.

Main Results:

• Order-sensitive meaning was found in female bigrams combining 'grunt' and 'twitter' calls.
• 'grunt_twitter' was associated with feeding, while 'twitter_grunt' occurred during infant-directed affiliations.
• Iterative call sequences also showed context-specific meaning shifts.

Conclusions:

• Meaningful combinatorial vocalizations extend beyond great apes and alarm contexts to monkeys.
• Sooty mangabeys demonstrate sophisticated use of call combinations in social interactions.
• Repertoire-wide use of meaning-shifting bigrams is not yet confirmed outside hominids.