Low frequency narrow-band calls in bottlenose dolphins (<i>Tursiops truncatus</i>): Signal properties, function, and conservation implications

Simard, Peter; Lace, Natalija; Gowans, Shannon; Quintana‐Rizzo, Ester; Kuczaj, Stan A.; Wells, Randall S.; Mann, David A.

doi:10.1121/1.3641442

Cited by 37 publications

(52 citation statements)

References 40 publications

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“…We included only those for which at least part of the fundamental frequency was above 3 kHz (Gridley, Berggren, Cockcroft, & Janik, 2012). This distinguishes whistles from other narrow-band sounds produced by bottlenose dolphins (Simard et al, 2011;van der Woude, 2009). Whistles interrupted by very short breaks (< 0.03 s) were considered as continuous, but no attempt was made to identify disconnected multiloops Janik et al, 2013) or signature whistles (Caldwell, Caldwell, & Tyack, 1990).…”

Section: Acoustic and Behavioural Analysismentioning

confidence: 99%

Changes in bottlenose dolphin whistle parameters related to vessel presence, surface behaviour and group composition

et al. 2016

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Cetacean watching from tour boats has increased in recent years and has been promoted as an ethically viable alternative to cetacean viewing in captive facilities or directed take. However, short-and long-term impacts of this industry on the behaviour and energetic expenditure of cetaceans have been documented. Although multiple studies have investigated the acoustic 1 response of dolphins to marine tourism, there are several covariates that could also explain some of these results and should be considered simultaneously. Here, we investigated whether common bottlenose dolphins, Tursiops truncatus, inhabiting Walvis Bay, Namibia vary their whistle parameters in relation to boat presence, surface behaviour and/or group composition. We detected an upward shift of up to 1.99 kHz in several whistle frequency parameters when dolphins were in the presence of one or more tour boats and the research vessel. No changes were demonstrated in the frequency range, number of inflection points or duration of whistles. A similar, although less pronounced difference was observed in response to engine noise generated by the research vessel when idling, suggesting that noise alone plays an important role in driving this shift in whistle frequency. Additionally, a strong effect of surface behaviour was observed, with the greatest difference in whistle parameters detected between resting and other behavioural states that are associated with higher degrees of emotional arousal. Group composition also contributed to the variation observed, with the impact of boats dependent on whether calves were present or not. Overall these results demonstrate high natural variation in the frequency parameters of whistles utilized by dolphins over varying behavioural states and group composition. Anthropogenic impact in the form of marine tour boats can influence the vocalization parameters of dolphins and such changes could have a long-term impact if they reduce the communication range of whistles or increase energy expenditure. Key wordsbottlenose dolphin, marine tourism, Namibia, Tursiops truncatus, vocal behaviour Wildlife tourism involving cetacean (whale, dolphin and porpoise) watching has experienced rapid growth since the 1990s (Hoyt, 2001;O'Connor, Campbell, Cortez, & Knowles, 2009). 2Globally, boat-based cetacean watching generates an estimated 2.2 billion US dollars annually (IWC, 2014). Revenue can provide a valuable subsidy to fishing communities and in some cases wild cetacean viewing has replaced direct hunting of whales and dolphins (Amir & Jiddawi, 2001;Berggren et al., 2007). Compared with captive facilities, responsible boatbased cetacean watching has been promoted as an ethically acceptable option for observing dolphins, providing a valuable forum for environmental education and promotion of conservation efforts (IFAW, 1997). However, a considerable body of work has shown that boats and boat-based cetacean watching can have multiple negative impacts on the behaviour of the focal individual, population or species (Parsons,...

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Section: Acoustic and Behavioural Analysismentioning

confidence: 99%

Changes in bottlenose dolphin whistle parameters related to vessel presence, surface behaviour and group composition

et al. 2016

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“…Brays are distinct vocal units composed of two constituent sound types: a BP and a short down sweep (Janik 2000a), the latter of which is structurally similar to an LFN sound (Simard et al 2011). We investigated the temporal patterning of BP and LFN sounds to look for evidence of bray production (dos Santos et al 1995;Janik 2000a).…”

Section: Acoustic Analysismentioning

confidence: 99%

“…LFN sounds are tonal signals with a short duration (,1 s) and confined to low frequencies (, 5 kHz, Simard et al 2011, Figure 2). To increase the probability of visually detecting LFN sounds, recordings were down-sampled from 96 to 32 kHz before scanning recordings.…”

Section: Acoustic Analysismentioning

confidence: 99%

“…Other bottlenose dolphin vocalizations, poorly described from an acoustic and behavioural perspective, include low-frequency moans (van der Woude 2009) and lowfrequency narrow-band (LFN) sounds (Schultz et al 1995;Simard et al 2011). Like BP sounds, their function in the dolphin acoustic repertoire has yet to be resolved.…”

Section: Introductionmentioning

confidence: 99%

“…Like BP sounds, their function in the dolphin acoustic repertoire has yet to be resolved. LFN sounds are short-duration (, 1 s) tonal sounds, usually under 1 kHz in frequency (Schultz et al 1995;Simard et al 2011). Although only recently described in detail (Simard et al 2011), they have likely always existed in the repertoire of bottlenose dolphins, perhaps classified under a different name.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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Describing the repertoire of sounds produced by wild cetaceans is necessary for understanding their function, for acoustic population monitoring and for measuring the potential influence of anthropogenic impact. Geographic variation in the types and parameters of sounds makes regional assessment of vocal behaviour necessary. We describe the acoustic repertoire of a small population of common bottlenose dolphins (Tursiops truncatus) inhabiting Walvis Bay, Namibia from recordings made over 59 encounters (72 h) between 2009 and 2012. The characteristics of burst pulse (BP) sounds, low-frequency narrow-band (LFN) sounds, brays, whistles and chirps are described. The BP sounds identified were generated at 150-1050 pulses per second, and most were short, lasting less than 1 s in duration. Bottlenose dolphins from Walvis Bay produce the lowest frequency LFN sounds described for the species. Whistles ranged in frequency from 1.58 to 23.24 kHz, and the mean acoustic parameters were within the range of those described from other geographic regions. Chirps were identified infrequently and usually as single occurrences. Although several sound types were often produced in close temporal succession, we found little evidence of stereotyped bray production, even during recordings of animals feeding. Our results demonstrate geographic variation in both the characteristics and sound types used by bottlenose dolphins and highlight the importance of regional data collection as a pre-curser to passive acoustic monitoring programmes.

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Whistle variation in Mediterranean common bottlenose dolphin: The role of geographical, anthropogenic, social, and behavioral factors

Manna¹,

Rako‐Gospić²,

Sarà

et al. 2020

Ecology and Evolution

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The studies on the variation of acoustic communication in different species have provided insight that genetics, geographic isolation, and adaptation to ecological and social conditions play important roles in the variability of acoustic signals. The dolphin whistles are communication signals that can vary significantly among and within populations. Although it is known that they are influenced by different environmental and social variables, the factors influencing the variation between populations have received scant attention. In the present study, we investigated the factors associated with the acoustic variability in the whistles of common bottlenose dolphin (Tursiops truncatus), inhabiting two Mediterranean areas (Sardinia and Croatia). We explored which factors, among (a) geographical isolation of populations, (b) different environments in terms of noise and boat presence, and (c) social factors (including group size, behavior, and presence of calves), were associated with whistle characteristics. We first applied a principal component analysis to reduce the number of collinear whistle frequency and temporal characteristics and then generalized linear mixed models on the first two principal components. The study revealed that both geographic distance/isolation and local environment are associated with whistle variations between localities. The prominent differences in the acoustic environments between the two areas, which contributed to the acoustic variability in the first principal component (PC1), were found. The calf's presence and foraging and social behavior were also found to be associated with dolphin whistle variation. The second principal component (PC2) was associated only with locality and group size, showing that longer and more complex tonal sound may facilitate individual recognition and cohesion in social groups. Thus, both social and behavioral context influenced significantly the structure of whistles, and they should be considered when investigating acoustic variability among distant dolphin populations to avoid confounding factors.

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Low frequency narrow-band calls in bottlenose dolphins (Tursiops truncatus): Signal properties, function, and conservation implications

Cited by 37 publications

References 40 publications

Changes in bottlenose dolphin whistle parameters related to vessel presence, surface behaviour and group composition

Changes in bottlenose dolphin whistle parameters related to vessel presence, surface behaviour and group composition

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

Whistle variation in Mediterranean common bottlenose dolphin: The role of geographical, anthropogenic, social, and behavioral factors

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