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The Bryde's whale (Balaenoptera edeni) is a species commonly documented along the southeast coast of Brazil, but nothing is known about their vocalizations in this area. Underwater recordings were gathered in an opportunistic manner when the species was present along the coast of the Rio de Janeiro State. A total of 143 min of recordings was analyzed, and five different call types were found. The most abundant call type consisted of a series of discrete pulses that was detected during the observation of a mother-calf pair. Other types of calls were recorded from solitary whales, including a flat tone with harmonics, a downswept tone, and two types of calls with multiple components. All recorded calls were short (< 2 s), with the exception of the series of pulses (> 7 s), with frequency ranges below 1 kHz. The call composed of a series of discrete pulses is likely linked to calf-adult interactions given that this call was previously reported in the presence of calves in the Gulf of California. This is the first description of the Bryde's whale vocal repertoire in the South Atlantic. The vocalizations described herein present generally identifiable characteristics of the species' calls; however, some variations may be specific to this area.

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According to the "signature whistle" hypothesis, dolphins emit stereotypic sequential whistles whose function is to transmit the identity and location of the whistling animal. However, it has also been proposed that the information signature may be expressed by distinct acoustical features within a single type of whistle shared by a population of dolphins. In an attempt to detect signature whistles from Sotalia guianensis living in Sepetiba Bay, Rio de Janeiro, Brazil, 12 h of vocalizations were recorded. Following analysis of the spectrograms, the whistles were classified according to visual inspection and the contour similarity method. Although the identities of the whistling animals were not established, 202 whistle sequences were selected and classified by visual inspection into 27 different types of potential signature whistles. However, there was a large discrepancy between this classification method and that obtained using the quantitative contour similarity method. The arguments in support of the premise that S. guianensis produces signature whistles are discussed and the limitations of the classification systems employed are examined.

Figueiredo, L.D.; Tardin, R.H.; Lodi, L.; Maciel, I.S.; Alves, M.A.S. & Simão, S.M. 2014. Site fidelity of Bryde's whales (Balaenoptera edeni) in Cabo Frio region, southeastern Brazil, through photoidentification technique. Braz. J. Aquat. Sci. Technol. 18(2): X-X. eISSN 1983-9057. DOI: 10.14210/bjast.v18n2.p59-64 Photo-identification technique was applied to Bryde's whales off the coast of Cabo Frio region, south-eastern Brazil between December 2010 and November 2012.Twenty-five individuals were sighted on nineteen different days and, of these total, nine were individually identified using natural marks on the dorsal fin. Of these, two individuals were seen in four different days, and one was seen in two occasions. The mean interval between re-sighting was 133 days (minimum: one day, maximum: 431 days). Two different adult individuals that were previously identified were seen again accompanied by calves and one of these was also seen next to the Rio de Janeiro city coast (126 km apart). Most of the observations consisted of lone individuals (58.8% of sightings). The data reported here indicate that the Cabo Frio coast may be important for the studied species in Brazilian waters and indicated the possible site fidelity of Bryde's whales to this area.

Sotalia fluviatilis was the only cetacean species observed in all 16 boat surveys (82 h) conducted in the Sepetiba Bay (22° 58′, 44° 02′W), between December 1993 and August 1995. During the boat survey of 5 January, 1995—a very calm day (Beaufort = 1)—it was possible to make good subaquatic sound recordings (30 min) of a group of ca. 20 young and subadult dolphins. As there is little bioacoustic information on tucuxi, sonogram analysis was used to characterize the tucuxi’s whistles of ascendent frequency. The qualitative analysis resulted in 866 whistles divided in 48 types. Some of these sonograms shapes match the ones presented by other cetacean species sonograms (Tursiops truncatus, Delphinus delphis, and Globicephala macrorhynchus). The quantitative analysis was based on: number of harmonics; number of inflexions; beginning, final, maximum, and minimum frequecies; duration; and frequency modulation. Minimum, maximum, and average values, standard deviation, and coefficient of variation were calculated for each type of whistle. The S. fluviatilis whistles are extremely diverse (high coefficient of variation values for each type) and frequent (38.5 whistles/min), seeming to have an important role in social relations among these animals. Such whistle diversity and quantities could be explained by the composition of the dolphin group, i.e, it was exclusively formed by young and subadult animals.

Animal vocalizations have nonlinear characteristics responsible for features such as subharmonics, frequency jumps, biphonation, and deterministic chaos. This study describes the whistle repertoire of a short-beaked common dolphin (Delphinus delphis) group at Brazilian coast and quantifies the nonlinear features of these whistles. Dolphins were recorded for a total of 67 min around Cabo Frio, Brazil. We identify 10 basic categories of whistle, with 75 different types, classified according to their contour shape. Most (45) of these 75 types had not been reported previously for the species. The duration of the whistles ranged from 0.04 to 3.67 s, with frequencies of 3.05–29.75 kHz. Overall, the whistle repertoire presented here has one of the widest frequency ranges and greatest level of frequency modulation recorded in any study of D. delphis. All the nonlinear features sought during the study were confirmed, with at least one feature occurring in 38.4% of the whistles. The frequency jump was the most common feature (29.75% of the whistles) and the nonlinear time series analyses confirmed the deterministic chaos in the chaotic-like segments. These results indicate that nonlinearities are a relevant characteristic of these whistles, and that are important in acoustic communication.