Geographic variations in the whistles of bottlenose dolphins (Tursiops aduncus) along the east and west coasts of Australia

Abstract

Macrogeographic variations in the structure and repertoire of whistles from four geographically separated bottlenose dolphin (Tursiops aduncus) populations from the east and west coasts of Australia were investigated. Microgeographic variations were examined from two adjacent social groups from the same east coast population. Whistles were divided into five different tonal classes; sine, rise, down-sweep, flat and concave. The acoustic parameters of whistles; start, end, low, high and carrier frequencies and the number of inflection points and harmonics were measured and compared. These features were used to identify and define distinct whistle types. Differences in acoustic parameters of whistles between populations varied with the tonal class and the acoustic parameter being tested and were likely to be driven by localized environmental conditions. There were few differences in the acoustic parameters of whistles between social groups which was likely a result of vocal learning and mimicry from intermixing of individuals. There were small percentages of distinct whistle types that were shared between the both intermixing social groups and geographically separated populations, however, the majority of the whistle repertoires were unique. The development of the unique whistle repertoires may be primarily driven by the complex social organization of the bottlenose dolphin.

Whistle characteristics of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in Sanniang Bay, China

“…Thus the data from Hong Kong cannot be extrapolated into the other regions. In addition, microgeographic and/or macrogeographic variations in dolphin whistles were frequently observed (Wang et al, 1995a;Baz ua-Dur an and Au, 2004;Azevedo and Sluys, 2005;Morisaka et al, 2005b;Hawkins, 2010).…”

“…Whistles are frequencymodulated narrowband sounds with the function including, but not limited to, communication between conspecifics (Janik, 2000), group organization, and cohesion (Janik and Slater, 1999;Janik, 2000;Janik et al, 2006). They have been widely adopted for species characterization (Baz uaDur an and Au, 2002;Azevedo et al, 2007;May-Collado and Wartzok, 2009) and for microgeographic and macrogeographic comparisons among different populations of the same species (Wang et al, 1995a;Baz ua-Dur an and Au, 2004;Azevedo and Sluys, 2005;Morisaka et al, 2005b;Hawkins, 2010) and among different species (Wang et al, 1995b;Wang et al, 2001;Oswald et al, 2003).…”

Whistle characteristics and daytime dive behavior in pantropical spotted dolphins (Stenella attenuata) in Hawai‘i measured using digital acoustic recording tags (DTAGs)

“…For example, whistle frequency parameters differ among populations of short-beaked common dolphins (Delphinus delphis; Ansmann et al, 2007), Indo-Pacific bottlenose dolphins (Tursiops aduncus; Hawkins, 2010), and common bottlenose dolphins (Tursiops truncatus; May-Collado and Wartzok, 2008). Furthermore, spectral and temporal whistle characteristics and vocal behavior are known to be influenced by factors such as group size, whistle type, behavior, stress and ambient noise levels (Morisaka et al, 2005;Ansmann et al, 2007;May-Collado and Wartzok, 2008;Rankin et al, 2008;Esch et al, 2009;Hawkins, 2010), which all may vary across time and space. Around the main Hawaiian Islands, three insular populations of pantropical spotted dolphins have recently been designated: an O'ahu stock, a 4-Island stock and a Hawai'i Island stock (Caretta et al, 2014).…”

“…A combined assessment of whistle characteristics from pantropical spotted dolphins in the ETP and in Hawai'i found minimum and maximum frequencies of 8.4 and 18.0 kHz, respectively (Oswald et al, 2007). However, because whistles from these populations were combined, the extent to which these parameters may vary among populations is not known; geographic variation in whistle characteristics has been documented in other delphinid species and could exist for pantropical spotted dolphins (e.g., Morisaka et al, 2005;Ansmann et al, 2007;May-Collado and Wartzok, 2008;Hawkins, 2010).…”

“…Baseline acoustic data are also necessary to inform passive acoustic monitoring (PAM), which is a leading method to study marine mammal occurrence, abundance, and habitat use (Jensen et al, 2009;van Parijs et al, 2009;Hawkins, 2010;Hatch et al, 2012;Marques et al, 2013;Risch et al, 2013). The development of automated detection and realtime monitoring systems (e.g., Oswald et al, 2007;Baumgartner and Mussoline, 2011) can improve the capabilities and cost-effectiveness of PAM-based surveys by reducing the staffing requirements at sea compared to visual sightings data.…”