How rhythmic are animal vocalizations?
Music is one of the few behaviors that clearly separates us from our closest relatives and it is unclear how music evolved. As opposed to the cultural phenomenon ‘music’, the basis for the construct ‘music’ can be described as ‘musicality’. Honing et al. (2015) define musicality as ‘a natural, spontaneously developing trait based on and constrained by biology and cognition‘. Their idea is to study music by examining the musicality of different animal species. Musical could for example be an animal’s response to pitch ratios or the temporal structure of conspecific vocalizations (for a review, see Hoeschele et al. 2015).
Rhythm is a key component of many different forms of music and can be investigated in animal vocalizations in different ways. Several important questions regarding rhythm in animal vocalizations exist: How stereotyped are rhythms in one individual, vocalization type, social group or even species? How good are animals in producing those rhythms?
Studies on rhythm in animal vocalizations are still scarce but cover a wide range of taxa. For instance, male zebra finch song has an individually distinct isochronous pulse (Norton & Scharff 2016), palm cockatoos use tools to ‘drum’ an isochronous beat on branches in a consistent context (Heinsohn et al. 2017), and male Northern Elephant Seals discriminate between familiar and unfamiliar male opponents using the temporal structure of vocalizations (Mathevon et al. 2017).
My former Ph.D. student Lara Burchardt investigated the temporal structure of animal vocalization on different levels, namely on the individual level, vocalization type level, and group level. She analyzed vocalizations of animals from different taxa, all sharing the ability to produce vocalizations while moving. This approach will give her insights into the relationship between functional rhythms such as a wing beat and the temporal structure of vocalizations. Species of interest are bats as well as baleen whales (since both taxa sing during locomotion). Also of interest are birds, in particular species with extensive flight songs such as skylarks.
With her dissertation project, Lara broadened our knowledge of temporal structures in animal vocalizations. Specifically, she wants to find out whether reoccurring temporal patterns can be found in individuals or groups, how close to a ‘perfect rhythm’ those are and how to best compare detected rhythms across taxa.