Whistle characteristics in free-ranging bottlenose dolphins ( Tursiops truncatus) in the Mediterranean Sea: Influence of behaviour

Abstract

Bottlenose dolphins ( Tursiops truncatus) are an extremely vocal mammalian species and vocal communication plays an important role in mediating social interactions. Very little is known about how wild bottlenose dolphins use whistles in different contexts and no data exist for context specificity of whistle characteristics. This study describes, for the first time in the Mediterranean Sea, the whistle characteristics of bottlenose dolphins in their natural repertoire. Over 35 h of behavioural observations and simultaneous recordings, 3032 tonal, frequency modulated whistles were detected. Our findings further support, for the first time in wild bottlenose dolphins, the suggestion that acoustic features may be good predictors of behavioural state and vice versa. These results advocate that these parameters may be used to communicate specific information on the behavioural context of the individuals involved. Additionally, visual inspection reveals that upsweeps and multi-looped whistles play an important role in the natural communication system of bottlenose dolphins. Likewise, this study demonstrates how dynamic bottlenose dolphin whistle characteristics are and how important it is to consider many factors in analysis. High intra-specific variability in whistle characteristics demonstrates its integral role in the complex social lives of wild bottlenose dolphins.