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

Abstract

a b s t r a c tBottlenose 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.

Dolphin changes in whistle structure with watercraft activity depends on their behavioral state

“…However, consistent recordings of groups with the same 47 dolphins in different combinations, behavioral states, and boat presence clearly suggest that interactions with dolphin watching boat are potentially harmful. This study adds further evidence that behavior contributes significantly to whistle variation within and among dolphin populations (e.g., Hawkins and Gartside, 2010;Hernandez et al, 2010;D ıaz L opez, 2011;May-Collado, 2013), and it provides preliminary evidence that dolphin-watching boat activities can prompt changes in local bottlenose dolphins whistle acoustic structure that are concordant with avoidance of signal masking by engine noise, particularly during foraging activities. Finally, our results also indicate that intrusive dolphin watching activities and associated engine noise may be negatively impacting individual fitness in this small dolphin population.…”

Changes in bottlenose dolphin whistle parameters related to vessel presence, surface behaviour and group composition

“…Azevedo et al, 2010;Díaz López, 2011;Hernandez et al, 2010;May-Collado, 2013). Several whistle types (Lilly, 1963;Rehn, Filatova, Durban, & Foote, 2011) or call combinations incorporating whistles have also been linked to high states of emotional arousal (see Herzing, 2000 for a review).…”

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

“…Common bottlenose dolphins inhabit tropical to temperate waters globally and occur around Australia in coastal as well as offshore waters [147,272]. Bottlenose dolphins have been acousti- [501] cally recorded in QLD, Australia [284], New Zealand [285], the Eastern Tropical Pacific [151,152], Hawaii [230], California [276,286], the Gulf of Mexico [163,253,276,287], the Caribbean [288], Central America [286,289], Brazil [270,290], Uruguay [291], Argentina [276], Namibia [292], the Northwest Atlantic [163,174], the Northeast Atlantic [282,293,294], Scotland and the UK [282,295,296], Mediterranean [156,293,[297][298][299], and Portugal [300]. Many recordings have also been taken of bottlenose dolphins in captivity (e.g.…”

“…Much of the literature focuses on whistles and geographic differences [151,152,156,163,174,253,270,276,286,[289][290][291][292][293][295][296][297][298]300,302]. Biphonic whistles have been reported [299].…”