Geographic variations in the whistles of spinner dolphins (Stenella longirostris)

Abstract

In order to better understand the reasons for geographic variations in the whistles of spinner dolphins (Stenella longirostris), recordings made in the Eastern Tropical Pacific will be compared to those recorded off Midway Atoll, Northwestern Hawai’ian Islands, the island of O’ahu, main Hawai’ian Islands, and Mo’orea, French Polynesia using discriminant function analysis. The values of 10 variables were extracted from the fundamental frequency (contour) of each whistle selected for analysis (begin, end, maximum, minimum and peak frequencies, center and peak times, duration, and number of turns and steps). Geographic variations in the whistles of spinner dolphins were found when comparing animals recorded in waters of Midway Atoll, off the main Hawai’ian Islands, and off Mo’orea. Greater differences were found between the Midway and Hawai’i and Mo’orea groups. The distinctiveness of Midway whistles could be due to geographic isolation and/or differences in population structure (habitat adaptation). The results indicate that geographic differences may not occur solely due to geographic isolation. Other factors, such as population structure and group size may be important when looking at differences in the whistles of spinner groups.

Whistle variability in South Atlantic spinner dolphins from the Fernando de Noronha Archipelago off Brazil

“…It is also known that spinner dolphin whistles can vary geographically ͑Bazúa- Durán and Au, 2001;Bazúa-Durán et al, 2003;Bazúa-Durán and Au, 2004͒, as it was already observed for bottlenose dolphins, Tursiops truncatus ͑Wang et al, 1995b;Jones and Sayigh, 2002͒, and for the estuarine dolphin, Sotalia guianensis ͑Azevedo and Van Sluys, 2005͒. Nevertheless, the factors influencing this observed geographic variation are still unclear, once the pattern found for spinner dolphins does not follow exactly those observed for the other two species.…”

“…O'ahu groups were very similar to TEP and Mo'orea groups, suggesting that there are no differences between oceanic and coastal spinner dolphin whistles. Bazúa-Durán and Au ͑2002͒ claimed that the distinctiveness of Midway whistles could be due to the stability of the spinner dolphins in that area, and that the geographic differences found may not occur solely due to geographic isolation, and that other factors, such as fluidity of the spinner dolphin groups may be also affecting this variation ͑Bazúa- Durán et al, 2003͒. In order to evaluate the variability of spinner dolphin whistles from the Fernando de Noronha Archipelago off Brazil ͑considered as S. longirostris longirostris͒, we conducted a series of quali-and quantitative analyses, which are presented here. No other study on this topic has been done in the Southwestern Atlantic Ocean.…”

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

“…The following standard whistle parameters (Baz ua-Dur an and Au, 2004;May-Collado and Wartzok, 2008) were measured: starting frequency (SF), ending frequency (EF), minimum frequency (MinF), maximum frequency (MaxF), delta frequency (DF), peak frequency (PF), duration (s), number of inflection points, and number of harmonics.…”

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).…”