Characteristics of whistles from rough-toothed dolphins (Steno bredanensis) in Rio de Janeiro coast, southeastern Brazil

Abstract

There is no information about the whistles of rough-toothed dolphins in the South Atlantic Ocean. This study characterizes the whistle structure of free-ranging rough-toothed dolphins recorded on the Rio de Janeiro coast, southeastern Brazil, and compares it to that of the same species in other regions. A total of 340 whistles were analyzed. Constant (N = 115; 33.8%) and ascending (N = 99; 29.1%) whistles were the most common contours. The whistles recorded had their fundamental frequencies between 2.24 and 13.94 kHz. Whistles without inflection points were frequently emitted (N = 255; 75%). Some signals presented breaks or steps in their contour (N = 97; 28.5%). Whistle duration was short (347 ± 236 ms and 89.7% of the whistles lasted <600 ms). Seventy-eight whistle contour types were found in the total of whistles analyzed, and 27 (7.9%) of these occurred only once. Most of the whistle types were unique to a particular recording session (N = 43). The signals emitted by the rough-toothed dolphins in southeastern Brazil were characterized by low frequency modulation, short duration, low number of inflection points, and breaks. Differences in the mean values of the whistle parameters were found between this and other studies that recorded Steno bredanensis, but as in other localities, whistles above 14 kHz are rare.

Trophic Relationships and Habitat Preferences of Delphinids from the Southeastern Brazilian Coast Determined by Carbon and Nitrogen Stable Isotope Composition

“…Rough-toothed dolphins are typically found in oceanic regions [55], but in Brazil they are commonly observed in shallow and coastal waters [55], [56], [57]. The results of the δ 13 C analysis suggest that the species uses continental shelf waters in southeastern Brazil, primarily foraging along the inner part of the shelf.…”

Vocalizations of the rough‐toothed dolphin, Steno bredanensis, in the Pacific Ocean

“…; Seabra de Lima et al . ). There are few descriptions of the full bandwidth of the echolocation clicks of S. bredanensis , and none that examine interclick interval (Norris and Evans , Baumann‐Pickering et al .…”

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

“…Five time and qualitative parameters were also extracted: Duration, beginning sweep (BS, down ¼ À1, flat ¼ 0, rise ¼ 1 and were transformed into the numeral 1, 2, and 3, respectively, during the statistical analyses), ending sweep (ES, down ¼ À1, flat ¼ 0, and rise ¼ 1, which were treated following the method of BS during statistical analyses), number of inflection points (NoIP; defined as points where the slope of the spectrogram contour changed from positive to negative or vice versa with both of the two-side frequency spans over 500 Hz), number of gaps (NoG; also defined as break of contour), number of stairs (NoS; defined as a continuous section of whistle with a sudden change in frequency of more than 500 Hz and the slope always nearly vertical), and additionally two extra harmonics (non-fundamental) parameters [i.e., number of harmonics (NoH) and the MaxF of harmonic (MHF)]. These variables were chosen because they were relatively easy to measure and are consistent with previous studies of humpback dolphins (Parijs and Corkeron, 2001b) and other dolphin species (Azevedo and Simão, 2002;Seabra de Lima et al, 2012) to facilitate comparisons among these studies. The frequency parameters were measured in Hz and time parameters in milliseconds (ms).…”