Fuzzy clustering as a tool to differentiate between discrete and graded call types.

Dana A Cusano,Rebecca A Dunlop,Michael J Noad

doi:10.1121/10.0005111

Abstract

Animals may communicate potential information to conspecifics using stereotyped "discrete" calls and variable "graded" calls. However, animal vocal research often centers on identifying the number of call types in a repertoire rather than quantifying the amount of gradation. Here, fuzzy clustering was applied to the social call repertoire of a species with a complex communication system, the humpback whale (Megaptera novaeangliae). Of 26 call types, 6 were classified as discrete, 7 as graded, and 13 as intermediate. These results indicate that humpback whales have a graded call repertoire, and fuzzy clustering may be a useful approach to investigate this variability.

Highlights

The vocal repertoires of non-human animals are presumably constrained to a finite number of call types (Hammerschmidt and Fischer, 2008)
Fuzzy clustering was applied to the social call repertoire of a species with a complex communication system, the humpback whale (Megaptera novaeangliae)
Of 26 call types, 6 were classified as discrete, 7 as graded, and 13 as intermediate. These results indicate that humpback whales have a graded call repertoire, and fuzzy clustering may be a useful approach to investigate this variability

Summary

Introduction

The vocal repertoires of non-human animals are presumably constrained to a finite number of call types (Hammerschmidt and Fischer, 2008). Animals have developed additional ways to convey potential information in calls. This includes variation in the acoustic features both within and between call types, which can convey information related to the signaler. This includes fixed information, which remains relatively stable over time (e.g., sex, individual identity, or age class) (Green and Marler, 1979), as well as flexible information, which varies with the internal state of the signaler (e.g., motivation or arousal) (Briefer, 2012; Marler, 1977). Graded calls are useful for group-based social situations, where the graded structure of calls provides information about the internal motivational state or arousal level of the signaler (Briefer, 2012; Marler, 1976; Morton, 1977)

Methods

Results

Conclusion