Nonlinear features in whistles produced by the short-beaked common dolphin (Delphinus delphis) off southeastern Brazil.

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.

Occurrence, residency patterns and habitat use of the bottlenose dolphin, Tursiops truncatus truncatus, on two Marine Protected Areas in Southeastern Brazil.

The common bottlenose dolphin, Tursiops truncatus, is widely distributed. However, information about its ecology and behavior in Brazilian waters is scarce especially about the 'offshore' ecotype, an Evolutionarily Significant Unit in the Southwest Atlantic. We report for the first time the occurrence, behavior and habitat use of bottlenose dolphins Tursiops truncatus truncatus, in two Marine Protected Areas (MPA) in Cabo Frio coast, Brazil. There were fifteen sightings of different groups throughout the year. An overall of 429 individuals were photo-identified. 90.7% dolphins did not present a degree of residence, 1.4% dolphins were considered with high residency to the area, 5.8% medium and 2.1% low. Our habitat use map indicated dolphins were more common off ~10km from Cabo Frio municipality and between depths around 20-70m. Bottlenose dolphins on Cabo Frio coast were more frequently observed performing travelling, followed by foraging and socio-sexual behavior. Group sizes varied from three to 120 individuals. Larger groups were observed when travelling and foraging. Despite the existence of two local Marine Protected Areas, the fast human development in Cabo Frio may threaten this important area for bottlenose dolphins in terms of food resources and shelter from predators.

Analysis of whistles produced by the Tucuxi Dolphin Sotalia fluviatilis from Sepetiba Bay, Brazil.

From July 2001 to June 2002, we recorded a total of 2 h 55 min of Tucuxi Dolphin Sotalia fluviatilis vocalizations from Sepetiba Bay, Brazil (22 degrees 35'S-44 degrees 03'W). A total of 3350 whistles were analyzed quantitative and qualitatively and were divided into 124 types, by visual inspection of sonograms. The following parameters were measured: Initial Frequency, Final Frequency, Minimum Frequency, Maximum Frequency, Duration, Number of Inflections, Frequency at the Inflection Points, Frequency at 1/2, 1/4, and 3/4 of whistle duration, Presence of Frequency Modulation and Harmonics. Ascending type whistles (N = 2719) were most common, representing 82% of the total. Dolphin behavior and average group size observed during recording influenced the whistle's quantitative and qualitative parameters. The results demonstrate the great diversity of whistles emitted and indicate a functional role of these vocalizations during the observed behaviors.

Analysis of whistles produced by the Tucuxi Dolphin Sotalia fluviatilis from Sepetiba Bay, Brazil

De julho de 2001 até junho de 2002, foram gravados um total de 2h55min de vocalizaçäes do Golfinho-Tucuxi Sotalia fluviatilis da Baía de Sepetiba, Brasil (22§35'S-44§03'W). Um total de 3350 assobios foram analisados quantitativa e qualitativamente e foram divididos em 124 tipos, pelo aspecto visual nos sonogramas. Os seguintes parâmetros foram medidos: Freqüência Inicial, Freqüência Final, Freqüência Mínima, Freqüência Máxima, Duração, Número de Inflecçäes, Freqüência nos Pontos de Inflecção, Freqüência a 1/2, 1/4, e 3/4 da duração do assobio, Presença de Modulação da Freqüência e Harmônicos. O tipo de assobio Ascendente (N=2719) foi o mais comum, representando 82% do total. O comportamento dos golfinhos e a média do tamanho do grupo observado durante as gravaçäes influenciaram os parâmetros de freqüência dos assobios quantitativa e qualitativamente. Os resultados demonstram grande diversidade dos assobios emitidos e indicam papel funcional destas vocalizaçäes durante os comportamentos.