Geographic variation in Risso's dolphin echolocation click spectra

Soldevilla, Melissa S.; Baumann‐Pickering, Simone; Cholewiak, Danielle; Hodge, Lynne; Oleson, Erin M.; Rankin, Shannon

doi:10.1121/1.4996002

Cited by 13 publications

(12 citation statements)

References 63 publications

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“…Because the sampling rate used in this study (50 kHz) did not allow us to record the full spectrum of echolocation clicks, we did not attempt to separate signals into probable species and pooled all acoustic data under a single delphinid group. Nevertheless, of the five dolphin species that occur in our study area 20 , Risso's dolphin clicks have peaks frequencies slightly higher than frequencies recorded by our system 61 . Moreover, in the Azores, Risso's dolphins show a preference for habitats close to the islands 16 and striped dolphins are only occasional visitors 20 .…”

Section: Discussioncontrasting

confidence: 55%

Temporal patterns in acoustic presence and foraging activity of oceanic dolphins at seamounts in the Azores

Cascão

Lammers

Prieto

et al. 2020

Sci Rep

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Several seamounts have been identified as hotspots of marine life in the Azores, acting as feeding stations for top predators, including cetaceans. Passive acoustic monitoring is an efficient tool to study temporal variations in the occurrence and behaviour of vocalizing cetacean species. We deployed bottom-moored Ecological Acoustic Recorders (EARs) to investigate the temporal patterns in acoustic presence and foraging activity of oceanic dolphins at two seamounts (Condor and Gigante) in the Azores. Data were collected in March–May 2008 and April 2010–February 2011. Dolphins were present year round and nearly every day at both seamounts. Foraging signals (buzzes and bray calls) were recorded in >87% of the days dolphin were present. There was a strong diel pattern in dolphin acoustic occurrence and behaviour, with higher detections of foraging and echolocation vocalizations during the night and of social signals during daylight hours. Acoustic data demonstrate that small dolphins consistently use Condor and Gigante seamounts to forage at night. These results suggest that these seamounts likely are important feeding areas for dolphins. This study contributes to a better understanding of the feeding ecology of oceanic dolphins and provides new insights into the role of seamount habitats for top predators.

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Section: Discussioncontrasting

confidence: 55%

Temporal patterns in acoustic presence and foraging activity of oceanic dolphins at seamounts in the Azores

Cascão

Lammers

Prieto

et al. 2020

Sci Rep

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“…, Soldevilla et al . ), thus highlighting the complex relationship between click structure and sound production morphology.…”

Section: Available Datamentioning

confidence: 97%

“…) but not all delphinid species (Soldevilla et al . ). Species producing this click subtype tend to have two slightly or moderately asymmetric bursae complexes, and their posterior melon has lateral branches that extend through unique pyramidal lipid basins to connect with both bursae complexes (Cranford et al .…”

Section: Available Datamentioning

confidence: 97%

Taxonomic revision of the dolphin genusLagenorhynchus

Vollmer

Ashe²,

Brownell

et al. 2019

Marine Mammal Science

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Evolutionary relationships among cetaceans within the family Delphinidae have been difficult to resolve due to the high number of species and their relatively rapid radiation. This is the case for the dolphin species currently placed in the genus Lagenorhynchus, and their relations to Cephalorhynchus and Lissodelphis species. Phylogenetic relationships among these species have been investigated using multiple lines of evidence, and that evidence consistently suggests that the six species currently assigned to Lagenorhynchus do not form a monophyletic group. Here, we summarize findings from studies of morphology, genetics, historical biogeography, and acoustics that offer insight into the phylogenetics of these taxa. We present the taxonomic basis for revision of Lagenorhynchus, propose retention of Lagenorhynchus albirostris and reassignment of the remaining five species into other existing generic names, namely Leucopleurus acutus, Sagmatias australis, Sagmatias cruciger, Sagmatias obliquidens, and Sagmatias obscurus. Making these revisions now so that the taxonomy better reflects evolutionary relationships among these species will ensure that future studies include the most appropriate taxa for investigating the 1 957 complex phylogenetic and systematic relationships among cetaceans. However, comprehensive analyses using multiple lines of evidence are still needed to clarify the phylogenetic relationships within and among the Lissodelphininae genera Cephalorhynchus, Lissodelphis, and Sagmatias.

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“…Previous research have also demonstrated that coefficients in cepstral analysis (inverse Fourier transform of the logarithm of the estimated spectrum of a signal) had good classification performance for some species (e.g. G. griesus, M. densirostris and G. macrorhynchus), with little influence of sound propagation and variation resulting from different recording platforms [15,63]. Additionally, energy amplitude, off-axis click distortion and transmission beam-widths may contain some species-specific information.…”

Section: Plos Onementioning

confidence: 99%

“…Acoustic parameters of odontocete clicks vary depending on their sound production morphology [14], with some species having the ability to optimize their clicks within the context of the specific habitat [15]. These parameters are further influenced by sound propagation [11], off-axis effects [16] and differences in recording systems [14].…”

Section: Introductionmentioning

confidence: 99%

Description and classification of echolocation clicks of Indian Ocean humpback (Sousa plumbea) and Indo-Pacific bottlenose (Tursiops aduncus) dolphins from Menai Bay, Zanzibar, East Africa

et al. 2020

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Passive acoustic monitoring (PAM) is a powerful method to study the occurrence, movement and behavior of echolocating odontocetes (toothed whales) in the wild. However, in areas occupied by more than one species, echolocation clicks need to be classified into species. The present study investigated whether the echolocation clicks produced by small, at-risk, resident sympatric populations of Indian Ocean humpback dolphin (Sousa plumbea) and Indo-Pacific bottlenose dolphin (Tursiops aduncus) in Menai Bay, Zanzibar, East Africa, could be classified to allow species specific monitoring. Underwater sounds of S. plumbea and T. aduncus groups were recorded using a SoundTrap 202HF in January and June-August 2015. Eight acoustic parameters, i.e.-10 dB duration, peak, centroid, lower-3 and lower-10 dB frequencies, and-3 dB,-10 dB and root-mean-squared bandwidth, were used to describe and compare the two species' echolocation clicks. Statistical analyses showed that S. plumbea clicks had significantly higher peak, centroid, lower-3 and lower-10 dB frequencies compared to T. aduncus, whereas duration and bandwidth parameters were similar for the two species. Random Forest (RF) classifiers were applied to determine parameters that could be used to classify the two species from echolocation clicks and achieved 28.6% and 90.2% correct species classification rates for S. plumbea and T. aduncus, respectively. Both species were classified at a higher rate than expected at random, however the identified classifiers would only be useful for T. aduncus monitoring. The frequency and bandwidth parameters provided most power for species classification. Further study is necessary to identify useful classifiers for S. plumbea. This study represents a first step in acoustic description and classification of S. plumbea and T. aduncus in the western Indian Ocean region, with potential application for future acoustic monitoring of species-specific temporal and spatial occurrence in these sympatric species.

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Geographic variation in Risso's dolphin echolocation click spectra

Cited by 13 publications

References 63 publications

Temporal patterns in acoustic presence and foraging activity of oceanic dolphins at seamounts in the Azores

Temporal patterns in acoustic presence and foraging activity of oceanic dolphins at seamounts in the Azores

Taxonomic revision of the dolphin genusLagenorhynchus

Description and classification of echolocation clicks of Indian Ocean humpback (Sousa plumbea) and Indo-Pacific bottlenose (Tursiops aduncus) dolphins from Menai Bay, Zanzibar, East Africa

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