Characterizing dusky dolphin sounds from Argentina and New Zealand

Abstract

Dusky dolphin (Lagenorhynchus obscurus) acoustic sounds were characterized by analyzing narrowband recordings [0-16 kHz in New Zealand (NZ) and 0-24 kHz in Argentina], and sounds in broadband recordings (0-200 kHz) were compared to their counterparts in down-sampled narrowband recordings (0-16 kHz). The most robust similarity between sounds present in broadband recordings and their counterparts in the down-sampled narrowband recordings was inter-click interval (ICI); ICI was therefore primarily used to characterize click sounds in narrowband recordings. In NZ and Argentina, distribution of ICIs was a continuum, although the distribution of ICIs in NZ had a somewhat bimodal tendency. In NZ, sounds that had smaller mean ICIs were more likely to have constant ICIs, and less likely to have increasing or decreasing ICIs. Similar to some other delphinids, dusky dolphins may use single, short duration sounds that have a constant ICI and closely spaced clicks for communication. No whistles were documented at either study site. Temporally structured sequences of burst pulses (i.e., sounds with ICI < about 10 ms) also occurred at both study sites, and these sequences contained 2-14 burst pulses that appeared closely matched aurally and in spectrograms and waveforms.

To buzz or burst-pulse? The functional role of Heaviside's dolphin, Cephalorhynchus heavisidii, rapidly pulsed signals

“…The study of rapidly pulsed acoustic sequences in cetaceans is in its infancy, and the functional role of repeated or patterned pulsed signals in most odontocetes is poorly understood. However, burstpulse sequences have been reported in several species including bottlenose dolphins, Tursiops truncatus (Overstrom, 1983;dos Santos, Ferreira, & Harzen, 1995), northern right whale dolphins, Lissodelphis borealis (Rankin, Oswald, Barlow, & Lammers, 2007), Pacific white-sided dolphins, Lagenorhynchus obliquidens (Henderson, Hildebrand, & Smith, 2011), white-beaked dolphins, Lagenorhynchus albirostris (Simard et al, 2008), dusky dolphins, Lagenorhynchus obscurus (Vaughn-Hirshorn et al, 2012) and Atlantic spotted dolphins, Stenella frontalis (Dudzinski, 1996;Herzing, 1996). Such reports indicate burst-pulse signals may be used in communicative exchanges or may indirectly broadcast signaller emotion to nearby listeners (Townsend & Manser, 2013).…”

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

“…Their frequent production by bottlenose dolphins seen in this and other studies (Blomqvist and Amundin 2004;Boisseau 2005) and stereotyped production by species such as the dusky dolphin (Lagenorhynchus obscurus) (Vaughn-Hirshorn et al 2012) and the northern right whale dolphin (Lissodelphis borealis) ) provides growing evidence that BP sounds play an important role in intra-specific communication. Communication using BP sounds may be particularly important in species that do not whistle (Dawson 1991) or whistle rarely Vaughn-Hirshorn et al 2012) and the function of BP sounds in whistling and non-whistling species may therefore differ. For example, in some species, the production of stereotyped BPs may encode individual or group (Ford 1991) identity.…”

“…The exact function of BP sounds remains unclear (Janik 2009) and may vary with species and context. There is growing evidence to support a principal role in communication (Lammers et al 2003b;Rankin et al 2007;Vaughn-Hirshorn et al 2012) rather than echolocation, as the inter-click interval (ICI, also referred to as the inter-pulse interval, IPI), which may be 10 ms or less (Lammers et al 2003a), exceeds the two-way propagation time thought necessary for receiving the echoes of individual clicks (Ivanov 2004). However, for long-range target discrimination, BP sounds may be used in an echolocation capacity (Ivanov 2004;Finneran 2013).…”

Taxonomic revision of the dolphin genusLagenorhynchus

“…; Vaughn‐Hirshorn et al . ). Following the assumption that production of whistles reflects evolutionary processes, these studies support that L. cruciger and L. australis are more similar to Cephalorhynchus species in that they do not produce whistles; L. borealis , L. obscurus , and L. obliquidens are similar to one another in that they are probably nonwhistlers or only whistle infrequently; and L. albirostris and L. acutus are more distinct from the other species as they retain whistles in their repertoire.…”