Differences in the whistle characteristics and repertoire of Bottlenose and Spinner Dolphins

Abstract

Several methods have been used to compare the whistles produced by dolphins. The two methods used in this study are: (1) a classification of whistle contours in six categories (i.e. constant frequency, upsweep, downsweep, concave, convex, and sine) and (2) the extraction of frequency and time parameters from each whistle contour. Bottlenose Dolphin Tursiops truncatus whistles are described in the same way when comparing whistle contour distributions in each of the six categories and whistle frequency and time parameters using Discriminant Function Analysis. For Spinner Dolphin Stenella longirostris whistles, each method describes whistles differently. Several facts may explain these differences in describing dolphin whistles, such as a greater fluidity of Spinner Dolphin groups when compared to Bottlenose Dolphin groups, greater geographic variation in the whistles of Bottlenose Dolphins than in those of Spinner Dolphins, an average beginning frequency 16% lower than the average ending frequency in Spinner Dolphin whistles compared to a varied relationship for Bottlenose Dolphins, and stricter criteria used to define whistle contour categories in the study of Spinner Dolphin whistles than in the Bottlenose Dolphin whistle study.

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

“…Secondly, throughout the entire study period, whistles were never recorded in presence of more than one group of bottlenose dolphins in the area. The inclusive definition of a dolphin focal group, to account for all individuals producing sound, was employed (Wang et al, 1995a(Wang et al, , 1995bErber and Simao, 2004;Bazúa-Durán, 2004;Morisaka et al, 2005;dos Santos et al, 2005;Boisseau, 2005;Pivari and Rosso, 2005;Azevedo et al, 2007;Baron et al, 2007;Quick and Janik, 2008) because during this study was not possible to ascertain which dolphin produced a whistle.…”

“…An inflection point is a change in the slope of the whistle contour from negative to positive, or vice versa (Pivari and Rosso, 2005). These whistle parameters were chosen both for consistency with previous acoustical studies (for example Erber and Simao, 2004;Bazúa-Durán, 2004;Morisaka et al, 2005;Pivari and Rosso, 2005;Azevedo et al, 2007;Baron et al, 2007), and because they could be easily measured manually from a spectrogram. Fig.…”

Tonal vocalizations in a noisy environment: an approach to their semi-automatic analysis and examples of its application

“…In particular, in research about dolphin whistles there is some dispute about this topic (see e.g. Buck and Tyack 1993, Janik 1999, McCowan and Reiss 2001, Bazúa-Durán 2004. Suggesting a single solution is clearly beyond the scope of this contribution.…”

Whistle comparison of four delphinid species in Southeastern Brazil

“…Whistle repertoires of delphinds have interspecific variations that may be influenced by many factors: differences in body sizes among species (May-Collado et al, 2007); degree of social fluidity (Baz ua-Dur an, 2004); phylogenetic relationships and zoogeographic relationships (May-Collado et al, 2007).…”