Whistles of Bottlenose Dolphins (<I>Tursiops truncatus</I>) in the Sado Estuary, Portugal: Characteristics, Production Rates, and Long-Term Contour Stability

Abstract

This study focuses on the whistle characteristics and production patterns of bottlenose dolphins (Tursiops truncatus) resident in the Sado Estuary, Portugal. Recordings and observations were conducted inside the estuary and in adjacent coastal waters using single hydrophones between 1987 and 2000. In the groups sampled, the mean number of whistles emitted per minute per animal was 0.28. The acoustic characteristics of a sample of 735 whistles were measured and compared with data from other Tursiops populations, showing that, in a pattern of overall similarity, the whistles recorded in the Sado are relatively long and the frequency range used is relatively wide. Mean peak frequency was 9.2 kHz. About 30% of the whistles were stereotyped, and remarkable stability was found in several contours over a 12-year period. No relation was found between dolphin group size and whistle rate, suggesting some restriction in production; and no relation was found between dolphin group size and the emission of different contours. Significant variation was found between episodes of simple travel and more aroused activities in terms of the production of whistles in general and also of different whistle contours.

Variation in the emission rate of sounds in a captive group of false killer whales Pseudorca crassidens during feedings: possible food anticipatory vocal activity?

“…This hypothesis could be supported by the overall increase of the rates of all sound classes during the pre-feeding intervals. Higher rates of whistles and burst pulses have been reported in dolphins during diff erent behavioral contexts characterized by high arousal levels (Busnel and Dziedzic, 1966;Smolker et al, 1993;Norris et al, 1994;Herzing, 1996;Acevedo-Gutiérrez and Stienessen, 2004;dos Santos et al, 2005). Moreover, clicks are normally used by dolphins during inquisitive behaviors (Supin et al, 2004(Supin et al, , 2005Nachtigall and Supin, 2008).…”

“…The diversity of sounds produced by this class of animals in various contexts provides evidence that they serve a highly communicative function (Kaznadzei et al, 1976;de Waal and Tyack, 2003;Marino et al, 2007). In fact dolphins, like the complex primates (Manser et al, 2002;Seyfarth and Cheney, 2003a, b), can modify the rate of specifi c sounds in order to transmit information related to behavioral events (dos Santos et al, 2005;Gardside, 2009a, b, 2010). Even though there is no indication of the presence of referential signals in dolphins' sounds as has been reported in primates (Cheney and Seyfarth, 1982), previous studies have suggested that the variations in the acoustic characteristics (rate and type of call) of the vocalizations of dolphins might be related to emotional states and specifi c events (Tavolga, 1983;Johnson, 1993;Herzing, 1996).…”

“…For example, modifi cations of the rate of the whistles have been observed in diff erent dolphin species during distinct behavioral contexts such as excitement and stress in Hawaiian spinner dolphins ( Stenella longirostris : Norris et al, 1994), during bow riding and feeding in common dolphins ( Delphinus delphis : Busnel and Dziedzic, 1966), feeding in pilot whales ( Globicephala sp. : Dreher and Evans, 1964), feeding, cooperative behavior, socialising (AcevedoGutiérrez and Stienessen, 2004;dos Santos et al, 2005), and mother/calf reunions in bottlenose dolphins (Smolker et al, 1993). The degree of exposure to human activities and interactions have also been found infl uential on the rate of the acoustic emissions of dolphins (Smolker et al, 1993;Scarpaci et al, 2000;Mann and Kemps, 2003;Morisaka et al, 2005;Hawkins and Gartside, 2009a, b ).…”

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

“…Common bottlenose dolphins inhabit tropical to temperate waters globally and occur around Australia in coastal as well as offshore waters [147,272]. Bottlenose dolphins have been acousti- [501] cally recorded in QLD, Australia [284], New Zealand [285], the Eastern Tropical Pacific [151,152], Hawaii [230], California [276,286], the Gulf of Mexico [163,253,276,287], the Caribbean [288], Central America [286,289], Brazil [270,290], Uruguay [291], Argentina [276], Namibia [292], the Northwest Atlantic [163,174], the Northeast Atlantic [282,293,294], Scotland and the UK [282,295,296], Mediterranean [156,293,[297][298][299], and Portugal [300]. Many recordings have also been taken of bottlenose dolphins in captivity (e.g.…”

The acoustic repertoire of wild common bottlenose dolphins (Tursiops truncatus) in Walvis Bay, Namibia

“…dos Santos et al 1995;Janik 2000aJanik , 2000bCook et al 2004;Boisseau 2005;dos Santos et al 2005;Frankel et al 2014). However, the majority of research has focused on echolocation clicks and whistles (e.g.…”