Using Rhythmic Notation and Musical Analysis on Animal Communication: A Case Study on Sperm Whales

Western music notation, a language of symbols representing various parameters in music, can be used to describe and analyze existing musical performances. Rhythmic elements such as periodicity and categorical rhythm have been studied in sperm whale (Physeter macrocephalus) codas, which are short click sequences produced in social interaction. As a case study in the applicability of music notation for animal communication, we transcribed human music, randomly generated rhythms, and sperm whale codas in Western music notation. Music notation categorizes sound elements into a metric hierarchy based on the perception of an isochronous beat in nonisochronous rhythms, a difficult comparison when we cannot know the rhythm perception of nonhuman animals. In accuracy and complexity, the transcriptions of codas showed similar statistics to the human rhythm samples. We demonstrated two modes of musical analysis on the transcriptions of sperm whale codas: tempo variation and motivic variation, and explored how they could be applied in ways that mitigate the subjective nature of interpreting beats. Our sample size was small, and our tools were time-consuming, so a streamlined approach is needed to fully test the applicability of these tools on a large scale.