The whistles of Hawaiian spinner dolphins

Abstract

The characteristics of the whistles of Hawaiian spinner dolphins (Stenella longirostris) are considered by examining concurrently the whistle repertoire (whistle types) and the frequency of occurrence of each whistle type (whistle usage). Whistles were recorded off six islands in the Hawaiian Archipelago. In this study Hawaiian spinner dolphins emitted frequency modulated whistles that often sweep up in frequency (47% of the whistles were upsweeps). The frequency span of the fundamental component was mainly between 2 and 22 kHz (about 94% of the whistles) with an average mid-frequency of 12.9 kHz. The duration of spinner whistles was relatively short, mainly within a span of 0.05 to 1.28 s (about 94% of the whistles) with an average value of 0.49 s. The average maximum frequency of 15.9 kHz obtained by this study is consistent with the body length versus maximum frequency relationship obtained by Wang et al. (1995a) when using spinner dolphin adult body length measurements. When comparing the average values of whistle parameters obtained by this and other studies in the Island of Hawaii, statistically significant differences were found between studies. The reasons for these differences are not obvious. Some possibilities include differences in the upper frequency limit of the recording systems, different spinner groups being recorded, and observer differences in viewing spectrograms. Standardization in recording and analysis procedure is clearly needed.

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

“…Successive contours were considered as one whistle if the gaps between them were shorter than 200 ms and shorter than the duration of the whistles with the former ending and the latter beginning section extended to form a smooth linkage, and an ending-beginning frequency difference of less than 3 kHz (Baz ua-Dur an and Au, 2002). Only one whistle was selected when a sequence of successive whistles with the same contour was encountered to minimize oversampling these possibly repeated whistles by the same dolphin.…”

“…Whistles achieving and exceeding the category "fair" were ascribed to the following six tonal types (definitions adapted from Baz ua-Dur an and Au, 2002): "Flat" (whistles with a frequency change span within1 kHz during more than 90% of duration, the frequency remained rarely constant for the entire duration of the signal) [ Fig. 2 "convex" (whistles initially mainly rising in frequency then mainly falling with only one increasing and one decreasing frequency span over 1 kHz and at least one inflection point) [Fig.…”

“…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).…”

Variation in the emission rate of sounds in a captive group of false killer whales Pseudorca crassidens during feedings: possible food anticipatory vocal activity?

“…All whistles included in the categories "fair" (whistles with main contour distinguishable and can be ascribed to a specifi c tonal type), "good" (whistles with a very clear contour and with the beginning and ending points well defi ned), and "fi ne" (whistles with a good signal to noise ratio over 20 dB) were counted for each of the fi ve intervals (Díaz López, 2011;Wang et al, 2013). Successive contours were considered as one whistles if the gap between them was smaller than 200 ms and shorter than the duration of both whistles, with the former ending and the latter beginning section extended to form a linkage, with the ending-beginning frequency diff erence less than 3 kHz ( Bazúa-Durán and Au, 2002 ). Whistles that overlapped were excluded from the analysis as well as the fragments of the recording containing dolphins vocalizing in the air.…”

Report of the Working Group on the Behavioral Ecology of bottlenose dolphins in the Southwest Atlantic Ocean

“…The bottlenose dolphin produces a wide repertoire of complex vocalizations, but the 'whistle' (a narrow band, frequency-modulated sound) is perhaps the category that receives most attention due to the social context in which it occurs (Wang et al, 1995a, b;Herzing, 1996;Bazúa Durán and Au, 2002;Lammers et al, 2003).…”