Signature whistles in free‐ranging populations of Indo‐Pacific bottlenose dolphins, Tursiops aduncus

Abstract

Common bottlenose dolphins (Tursiops truncatus) use individually distinctive signature whistles which are highly stereotyped and function as contact calls. Here we investigate whether Indo-Pacific bottlenose dolphins (T. aduncus) use signature whistles. The frequency trace of whistle contours recorded from three genetically distinct free-ranging populations was extracted and sorted into whistle types of similar shape using automated categorization. A signature whistle identification method based on the temporal patterns in signature whistle sequences of T. truncatus was used to identify signature whistle types (SWTs). We then compared the degree of variability in SWTs for several whistle parameters to determine which parameters are likely to encode identity information. Additional recordings from two temporarily isolated T. aduncus made during natural entrapment events in 2008 and 2009 were analyzed for the occurrence of SWTs. All populations were found to produce SWTs; 34 SWTs were identified from recordings of free-ranging T. aduncus and one SWT was prevalent in each recording of the two temporarily isolated individuals. Of the parameters considered, mean frequency and maximum frequency were the least variable and therefore most likely to reflect identity information encoded in frequency modulation patterns. Our results suggest that signature whistles are commonly used by T. aduncus.

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

“…CW sounds are mostly lumped with FM sounds and their parameters are therefore not always listed separately [280]. T. aduncus have been shown to produce signature whistles [281]. Echolocation clicks cover a frequency band from 45 to 109 kHz with a peak frequency of 124 ± 13 kHz, last 18 ± 6 µs, with an ICI of 63 ± 45 ms and source levels of 205 ± 7 dB re 1 µPa pp @ 1 m, 195 ± 4 dB re 1 µPa rms @ 1 m and 146 ± 7 dB re 1 µPa 2 s @ 1 m [241,282].…”

Mother-Offspring Signature Whistle Similarity and Patterns of Association in Atlantic Spotted Dolphins (Stenella frontalis)

“…Our knowledge of signature whistles is almost entirely based on bottlenose dolphin studies (Harley, 2008;Tyack, 1997). However, signature whistles have been described for the Atlantic spotted dolphin (Stenella frontalis: Caldwell & Caldwell, 1966;Caldwell, Caldwell, & Miller, 1973;Herzing, 1996) and a few other dolphin species (common dolphin, Delphinus delphis: Caldwell & Caldwell, 1968; Pacific whitesided dolphin, Lagenorhynchus obliquidens: Caldwell & Caldwell, 1971; Indo-Pacific bottlenose dolphin, T. aduncus: Gridley et al, 2014, as well as probable signature whistles in Risso's dolphin, Grampus griseus : Caldwell, Caldwell, & Miller, 1969;Guiana dolphin, Sotalia guianesis: de Figueiredo & Simão, 2009; Pacific humpback dolphin, Sousa chinensis: Van Parijs & Corkeron, 2001). Research assessing signature whistles in Atlantic spotted dolphins is limited (Burris, 2004;Herzing, 1996;Herzing, Deecke, & Brunnick, 1999), as a result, works cited in this paper refer to bottlenose dolphins unless otherwise noted.…”

Bioacoustic Spectral Whistle Sound and Behaviour of Male Dolphin Bottle Nose (Tursiops aduncus) at Safari Park Indonesia, Cisarua Bogor

“…From the results obtained can be identified as the whistle sounds emanating from dolphins by calculating or viewing range interval whistle sound itself [16]. Highest intensity on a whistle 4 can also be affected by the position with the position of the dolphin is horizontal, because according to [17][18][19][20] movement in the vertical position will probably affect the magnitude of the sound and the inconsistency of the sound emitted by the dolphins using conservation methods energy obtained by dolphins, and will require a lot of energy to expend greater voice intensity value (Table 1).…”

“…Dolphins are more dominant on the surface at the time before eating, and behavior of dolphins is more inclined to the surface of the pool. The position of the dolphins is very influential on the resulting frequency [5,6,18,20].…”