Variation in Guiana dolphin (Sotalia guianensis) whistles: using a broadband recording system...

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acta ethol DOI 10.1007/s10211-014-0183-7

ORIGINAL PAPER

Variation in Guiana dolphin (Sotalia guianensis) whistles: using a broadband recording system to analyze acoustic parameters in three areas of southeastern Brazil Luciana Guimarães de Andrade & Isabela Maria Seabra Lima & Halerson da Silva Macedo & Rafael Ramos de Carvalho & José Lailson-Brito Jr. & Leonardo Flach & Alexandre de Freitas Azevedo

Received: 21 June 2013 / Revised: 9 October 2013 / Accepted: 13 February 2014 # Springer-Verlag Berlin Heidelberg and ISPA 2014

Abstract The Guiana dolphin produces a variable whistle repertoire related to different social contexts. The current study evaluates Guiana dolphin whistles at a microscale. Acoustic parameters of whistles were compared between three areas in southeastern Brazil using a recording system with sampling rate of 96 kHz. Previous studies that utilized a sampling rate of 48 kHz reported little variation between adjacent areas in Brazil. Nine acoustic parameters of the whistles (duration, start, end, minimum and maximum frequencies, delta frequency, frequency at 1/4, 1/2, and 3/4 of duration) were measured and whistles were classified into five contour forms. A total of 659 whistles were analyzed, of which 62.20 % showed an ascending contour form. The Guiana dolphin emitted whistles with a fundamental frequency reaching 44.9 kHz. Dolphin whistles from the three study areas varied significantly in nine acoustic parameters. The whistle duration was shorter (272.44 ± 105.25 ms) in Guanabara Bay than those in Sepetiba (360.05±135.16 ms) and Paraty Bays (376.80±159.78 ms). The start and minimum frequencies of the whistles in Guanabara Bay was significantly higher than those in Sepetiba and Paraty Bays. The results L. G. de Andrade : J. Lailson-Brito Jr. : A. de Freitas Azevedo Pós-Graduação em Ecologia e Evolução (PPGEE), Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, Maracanã, Rio de Janeiro 20550-013, Rio de Janeiro, Brazil L. G. de Andrade (*) : I. M. Lima : H. da Silva Macedo : R. R. de Carvalho : J. Lailson-Brito Jr. : A. de Freitas Azevedo Faculdade de Oceanografia (FAOC), Laboratório de Mamíferos Aquáticos e Bioindicadores (MAQUA), Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, Maracanã, Rio de Janeiro 20550-013, Rio de Janeiro, Brazil e-mail: andrade.uerj@gmail.com L. Flach Instituto Boto Cinza, Rua Santa Terezinha 531, Rio de Janeiro 23860-000, Rio de Janeiro, Brazil

of discriminant function analysis indicated a significant difference between Guanabara Bay and the other two areas. Comparisons of the ascending, descending–ascending, and multi whistles between areas showed differences in some acoustic parameters. In this study, by doubling the sampling rate in our recording systems, we were able to more accurately sample the whistle repertoire of Guiana dolphins in southeastern Brazil, and thereby detect differences in whistles between neighboring populations. Keywords Sotalia guianensis . Whistles . Microscale variation . Bioacoustic

Introduction Delphinids produce a variety of acoustic emissions used in different behavioral contexts, including recruitment during feeding activities and group cohesion (Caldwell et al. 1990; Richardson et al. 1995; Tyack 2000; Podos et al. 2002). Dolphin acoustic signals are divided into two broad categories: whistles (tonal sounds) and pulsed sounds (Richardson et al. 1995). Whistles are continuous, narrow-band sounds that often exhibit frequency modulation and harmonics (Richardson et al. 1995; Tyack 2000). Fundamental frequencies of whistles are typically between 800 and 28.5 kHz, with durations between 100 ms and 4 s (Schultz and Corkeron 1994; Buckstaff 2004; Janik 2009). This type of sound emission is used mainly in social contexts such as group coordination, behavioral activities, and individual identification (e.g., Caldwell et al. 1990; Janik et al. 1994; Herzing 2000; Van Parijs and Corkeron 2001; Pivari and Rosso 2005; Janik 2009; Díaz López 2011). Several studies have used qualitative analyses (related to variations in the contour form) and quantitative analyses (duration and frequency measurements) of whistles to characterize


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