Identification and Characteristics of Signature Whistles in Wild Bottlenose Dolphins (Tursiops truncatus) from Namibia

Kriesell, Hannah Joy; Elwen, Simon Harvey; Nastasi, Aurora; Gridley, Tess

doi:10.1371/journal.pone.0106317

Cited by 53 publications

(82 citation statements)

References 76 publications

(148 reference statements)

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“…The differences in duration observed could therefore also be explained by increased rates of signature whistle production by adult animals, possibly mothers during separations from their offspring in the mother-calf groups (Mello & Amundin, 2005;Sayigh et al, 1990;Smolker, Mann, & Smuts, 1993). As in other studies (Hawkins & Gartside, 2010), calf presence in this population is highly correlated with group size, with calves being present in larger groups (Kriesell et al, 2014). Consequently the influence of calf presence and group size on whistle parameters cannot easily be disentangled.…”

Section: Discussionmentioning

confidence: 60%

“…This might be explained by the fact that a substantial proportion of the whistle repertoire of the common bottlenose dolphin population in Walvis Bay includes signature whistles (Kriesell et al, 2014). Bottlenose dolphins commonly extend or reduce the duration of their signature whistles (Deecke & Janik, 2006;Sayigh, Tyack, Wells, & Scott, 1990), and this time warping relates to behavioural context (Esch, Sayigh, Blum, et al, 2009;Janik, Dehnhardt, & Todt, 1994;this study).…”

Section: Discussionmentioning

confidence: 94%

“…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). Signature whistles in this population are described elsewhere (Kriesell, Elwen, Nastasi, & Gridley, 2014). …”

Section: Acoustic and Behavioural Analysismentioning

confidence: 99%

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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: Discussionmentioning

confidence: 60%

Section: Discussionmentioning

confidence: 94%

Section: Acoustic and Behavioural Analysismentioning

confidence: 99%

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

et al. 2016

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“…Compared with LFN sounds, whistles were highly variable in structure, particularly with regard to the duration, inflection points and frequency range (CVs of 45 or more). Whistles were often produced in sequences containing repetitions of the same whistle type, providing strong evidence of signature whistle production Kriesell et al 2014) in the Walvis Bay population.…”

Section: Resultsmentioning

confidence: 92%

“…Whistles interrupted by very short breaks (,0.03 s) were considered as continuous, but no attempt was made to identify disconnected multiloops (Esch et al 2009b;Janik et al 2013) or signature whistles (Caldwell et al 1990) in the whistle repertoire. Signature whistles in this population are described elsewhere (Kriesell et al 2014). Geographic variation in whistle parameters was assessed by comparing our mean values for 6 standard whistle parameters with published data from 12 other regions where the mean and standard deviation (SD) of the vocalization parameter were available.…”

Section: Acoustic Analysismentioning

confidence: 99%

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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Acoustic detection of bottlenose dolphin depredation on nets and implications for conservation

Manna

Arrostuto

Campisi

et al. 2022

Aquatic Conservation

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Understanding the depredation process is pivotal to the management of conflicts between wildlife and human activities. Depredation by marine mammals on fisheries occurs when animals ‘steal’ fish from the fishing gear, causing catch loss and damage to gear and catches. The common bottlenose dolphin is a vulnerable species and is the main depredator of coastal static net fisheries in the Mediterranean Sea. The nature and extent of the phenomenon is still poorly understood since evidence is often incomplete or inconsistent mostly due to the different methods used to measure depredation. Here, passive acoustic monitoring devices were used to estimate the consistency between dolphin acoustic detection in proximity to the net and direct dolphin observations and catch measurements at different sites in Sardinia (north‐western Mediterranean Sea). Further, some factors influencing depredation (fishing duration and fishing net length) and changes in catch amount and composition were evaluated. The frequency of dolphin detection based on direct dolphin observations was significantly lower than that based on acoustic monitoring; the latter was related to the amount of catch. Thus, the measurement of catch was more realistically related to depredation than direct dolphin observations. Further, dolphin depredation was related to the duration of the fishing operation. The measure of depredation and catch loss provided here can be used to realistically estimate the damage suffered by fishers and provide preliminary insights to guide the development of an approach for sustainable coexistence between dolphins and fisheries.

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Identification and Characteristics of Signature Whistles in Wild Bottlenose Dolphins (Tursiops truncatus) from Namibia

Cited by 53 publications

References 76 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

Acoustic detection of bottlenose dolphin depredation on nets and implications for conservation

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