Geographic variations in the whistles of spinner dolphins ( Stenella longirostris ) of the Main Hawai‵ian Islands

A series of quali-and quantitative analyses were conducted to evaluate the variability of spinner dolphin whistles from the Fernando de Noronha Archipelago off Brazil. Nine variables were extracted from each whistle contour, and the whistle contours shapes were classified into the seven categories described in Driscoll ͑1995͒. The analysis showed mean beginning and ending frequencies values of 10.78 and 12.74 kHz, respectively. On average, whistle duration was relatively short, with mean values around 0.495 s ͑N = 702͒. Comparative analyses were also conducted to investigate the relationship between the obtained results and those presented in previous studies. When comparing averages, the results of the study of Oswald et al.͑2003͒ in the Tropical Eastern Pacific ͑TEP͒ presented less significant differences in relation to this study; only whistle duration differed significantly between both works. The results of multivariate classification tests also pointed TEP population as the closest related to the population studied here. The similarities between such disjunct populations might be attributed to a more recent isolation event ͑the closing of the Panama Isthmus͒ than the divergence that has driven North and South Atlantic populations apart.

Section: Introductionmentioning

confidence: 79%

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

Camargo

Rollo²,

Giampaoli

et al. 2006

“…g. Herzing, 1996;Van Parijs et al, 2000;Bazúa-Durán and Au, 2004͒ and they seem to be related to whistle functions, which include to transmit emotional states and to coordinate dolphin activities ͑Tyack, 1998͒. Whistles produced by Atlantic spotted dolphins varied among the two behavioral states in which dolphins were engaged.…”

Section: Discussionmentioning

confidence: 98%

“…These signals have been the focus of several bioacoustic studies on delphinids due to the numerous easily measured characteristics presented by them. In addition, they have been used for characterization and comparisons among groups and populations ͑e.g., Rendell et al, 1999;Bazúa-Durán and Au, 2004;Azevedo and Van Sluys, 2005;May-Collado and Wartzok, 2009͒. Atlantic spotted dolphins ͑Stenella frontalis͒ are found in warm temperate to tropical waters in Atlantic Ocean ͑Jef-ferson et al, 2008͒. As most delphinids, this species is a highly vocal dolphin species that produces echolocation click trains, burst pulse sounds, and whistles related to behavioral activities ͑Perrin, 2002͒.…”

Section: Introductionmentioning

confidence: 98%

Whistles emitted by Atlantic spotted dolphins (Stenella frontalis) in southeastern Brazil

Azevedo

Flach²,

Bisi

et al. 2010

The whistles of Atlantic spotted dolphins have been studied in a few localities of the North Atlantic Ocean and those studies revealed that the species emits whistles within a broad frequency range, with a high number of inflection points and presence of harmonics. In the South Atlantic Ocean, there is no information about the sounds produced by Atlantic spotted dolphins. A total of 1092 whistles emitted by free-ranging Atlantic spotted dolphins in Southeastern Brazilian coastal waters were analyzed. Whistles recorded in this study had a broad frequency range from 1.15 to 23.44 kHz. Whistles without harmonics were frequently emitted (N=701; 64.2%) and those signals with zero up to two inflection points corresponded to 94% of all whistles. Some differences in whistle characteristics (inflection points and duration) were found in relation to areas in North Atlantic Ocean and whistles were shorter and with a smaller number of inflection points in Brazil. Whistles produced by Atlantic spotted dolphins varied between the two behavioral states in which dolphins were engaged. Whistles were more frequently emitted when dolphins presented behaviors that included fast movement at surface, prey pursuit, aerial behavior, and physical contact. In these situations, whistles were on average longer and had higher frequency parameters than those emitted when animals were engaged in slowly and moderate traveling. The findings presented herewith reveal that dolphins modified whistle structures within behavioral states.

“…These three frequency measurements are standard in Guyana dolphin whistle studies ͑see Azevedo and Van Sluys, 2005;Erber and Simão, 2004;Rossi-Santos and Podos, 2006͒. Peak frequency ͑PF͒ was also measured and is defined as the frequency at which maximum power occurs ͑Bazúa-Durán and Au, , 2004May-Collado and Wartzok, 2007͒ and number of harmonics ͑e.g., Wang et al, 1995;Erber and Simão, 2004͒. Whistle contours were categorized as ascending, descending, ascending-descending, descending-ascending, and constant in frequency, sine, and others ͑see Azevedo and Van Sluys, 2005; Erber and Simão, 2004͒.…”

Section: B Whistle Recordings and Analysismentioning

confidence: 99%

“…Seven standard whistle variables were measured on the fundamental frequency of each: starting frequency ͑SF͒, ending frequency ͑EF͒, minimum frequency ͑MinF͒, maximum frequency ͑MaxF͒, delta frequency ͑DF= MaxF− MinF͒, duration ͑s͒, and number of inflection points ͑see, e.g., Wang et al, 1995;Oswald et al, 2003Oswald et al, , 2004Erber and Simão 2004; Bazúa-Durán and Au, , 2004Azevedo and Van Sluys, 2005;Baron et al, 2008͒. In addition, the contour was divided into four parts equally distributed in time to measure the frequency at 1 4 , 1 2 , and 3 4 of the contour. These three frequency measurements are standard in Guyana dolphin whistle studies ͑see Azevedo and Van Sluys, 2005;Erber and Simão, 2004;Rossi-Santos and Podos, 2006͒.…”

Section: B Whistle Recordings and Analysismentioning

confidence: 99%

A characterization of Guyana dolphin (Sotalia guianensis) whistles from Costa Rica: The importance of broadband recording systems

May‐Collado

Wartzok

2009

Knowledge of the whistle structure in Guyana dolphins comes mostly from Brazilian populations where recordings have been made using limited bandwidth systems (18 and 24 kHz). In Brazil, Guyana dolphin whistle frequency span is 1.34-23.89 kHz, but authors have suggested that limits of their recording system may underestimate frequency span. Whistles of Guyana dolphins from Costa Rica were studied using a broadband recording system. How bandwidth limitations affect the understanding of whistle structure and species classification between sympatric dolphin species was evaluated. In addition, whistles were compared to Brazilian populations. Guyana dolphin whistle frequency span was 1.38 up to 48.40 kHz, greater than previously reported. Bandwidth limitations explained 89% of the whistle variation between studies, and increase in bandwidth improved the whistle classification of Guyana dolphins. Whistle duration and minimum frequency were the most important variables in dolphin species classification. Finally, after accounting for differences in recording systems, Costa Rican Guyana dolphins whistled with significantly higher frequency than Brazilian populations, providing evidence for a postulated increase in frequency from south to north. The study concludes that equipment with an upper frequency limit of at least 50 kHz (150 kHz for harmonics) is required to capture the entire whistle repertoire of the Guyana dolphin.