Abstract
Two language laws have been identified as manifestations of universal principles of animal behaviour, both acting on the organisation of numerous vocal and behavioural communicative systems. Zipf’s law of brevity describes a negative relationship between behavioural length and frequency of behaviour. Menzerath’s law defines a negative correlation between the number of behaviours in a sequence and average length of the behaviour composing it. Both laws have been linked with the information-theoretic principle of compression, which tends to minimise code length. We investigate the presence of these two laws in the repertoire of chimpanzee sexual solicitation gestures. We find that chimpanzee solicitation gestures do not follow either Zipf’s law of brevity or Menzerath’s law consistently. For the second time in ape gestural communication, evidence supporting Zipf’s law of brevity was absent, and, here, the presence of Menzerath’s law appears individually driven. Ape gesture does not appear to manifest a principle of compression or pressure for efficiency that has been previously proposed to be universal. Importantly, the same signals were shown to adhere to these laws when used in a different behavioural context; highlighting that signallers consider signalling efficiency broadly, and diverse factors play important roles in shaping investment in signal production.
Competing Interest Statement
The authors have declared no competing interest.
