Beam pattern estimation of clicks of a free-ranging Ganges river dolphin

Bahl, Rajendar; Sugimatsu, Harumi; Kojima, Junichi; Ura, Tamaki; Behera, Sandeep; Inoue, Tomoki; Fukuchi, Tetsuo

doi:10.1109/oceans.2007.4449286

Cited by 13 publications

(6 citation statements)

References 4 publications

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“…Beam patterns have been directly measured under laboratory conditions for Tursiops truncatus (Au et al, 1978;Au et al, 1980;Au et al, 1986), Delphinapteus leucas (Au et al, 1987), Pseudorca crassidens (Au et al, 1995) and Phocoena phocoena (Au et al, 1999), and have been estimated from field recordings of Lagenorhynchus albirostris (Rasmussen at al., 2004), Platanista gangetica (Bahl et al, 2007), Physeter macrocephalus (Mohl et al, 2003) and Ziphius cavirostris (Zimmer et al, 2005a). Most odontocete signals measured thus far have 3dB beamwidths (the angle at which the beam's power is half the maximum power of the signal) between 8 and 15deg, with interspecific and intraspecific variation (Au, 1993).…”

Section: Introductionmentioning

confidence: 99%

Active echolocation beam focusing in the false killer whale, Pseudorca crassidens

Kloepper

Nachtigall

Donahue

et al. 2012

Journal of Experimental Biology

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SUMMARYThe odontocete sound production system is highly complex and produces intense, directional signals that are thought to be focused by the melon and the air sacs. Because odontocete echolocation signals are variable and the emitted click frequency greatly affects the echolocation beam shape, investigations of beam focusing must account for frequency-related beam changes. In this study we tested whether the echolocation beam of a false killer whale changed depending on target difficulty and distance while also accounting for frequency-related changes in the echolocation beam. The data indicate that the false killer whale changes its beam size according to target distance and difficulty, which may be a strategy of maximizing the energy of the target echo. We propose that the animal is using a strategy of changing the focal region according to target distance and that this strategy is under active control.

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Section: Introductionmentioning

confidence: 99%

Active echolocation beam focusing in the false killer whale, Pseudorca crassidens

Kloepper

Nachtigall

Donahue

et al. 2012

Journal of Experimental Biology

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“…); these are short pulses of about 40 μs with a dominant frequency of 65 kHz (Bahl et al . ). Indus River dolphins ( Platanista gangetica minor ) are also nearly blind and constantly produce echolocation pulses (Pilleri ).…”

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confidence: 97%

Diel changes in the movement patterns of Ganges River dolphins monitored using stationed stereo acoustic data loggers

Sasaki-Yamamoto

Akamatsu

Ura

et al. 2012

Marine Mammal Science

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We monitored the underwater movements of Ganges River dolphins using stationed stereo acoustic data loggers. We estimated these movements using changes in the relative angle of the sound source direction (trajectory). Of the total acoustic recordings (66 h), 26.2% contained trajectories of dolphins, and 78.6% of these trajectories involved single animals, suggesting that dolphins tended to swim alone and were localized near the monitoring station. The observed trajectories were categorized as follows: staying type characterized by small changes in the sound source direction, moving type A (moving in the same direction), and moving type B (moving up and down the stream during recording). The average interpulse intervals of sounds in moving types A and B were significantly shorter than that of the staying type, suggesting that dolphins produce the former types of trajectories to echolocate across shorter distances during movement. The frequency of occurrence of moving type A increased during the night, whereas that of type B increased in the late afternoon and that of the staying type increased during the daytime. These results indicate that dolphins moving at night tended to use short‐range echolocation, whereas during the day, they remained in relatively small areas and used long‐range sonar.

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“…Although to date no research has been conducted on the beam directionality in botos and tucuxis, these results are consistent with the sharply directional beam observed in botos. The Ganges river dolphin has fairly narrow beam directionality (Ura et al, 2007;Bahl et al, 2007). Although the Ganges river dolphin and boto are phylogenetically separate (Nikaido et al, 2001), the sharp beam pattern could provide higher spatial resolution in shallow waters comprising a complex environment.…”

Section: Discussionmentioning

confidence: 99%

Acoustic characteristics of biosonar sounds of free-ranging botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the Negro River, Amazon, Brazil

Yamamoto

Akamatsu

Silva

et al. 2015

The Journal of the Acoustical Society of America

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Odontoceti emit broadband high-frequency clicks on echolocation for orientation or prey detection. In the Amazon Basin, two odontoceti species, boto (Amazon River dolphin, Inia geoffrensis) and tucuxi (Sotalia fluviatilis), live sympatrically. The acoustic characteristics of the echolocation clicks of free-ranging botos and tucuxis were measured with a hydrophone array consisting of a full-band and an acoustic event recorder (A-tag). The clicks of the two species were short-duration broadband signals. The apparent source level was 201 dB 1 μPa peak-to-peak at 1 m in the botos and 181 dB 1 μPa peak-to-peak at 1 m in the tucuxis, and the centroid frequency was 82.3 kHz in the botos and 93.1 kHz in the tucuxis. The high apparent source level and low centroid frequency are possibly due to the difference in body size or sound production organs, especially the nasal structure, the sound source of clicks in odontoceti.

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Beam pattern estimation of clicks of a free-ranging Ganges river dolphin

Cited by 13 publications

References 4 publications

Active echolocation beam focusing in the false killer whale, Pseudorca crassidens

Active echolocation beam focusing in the false killer whale, Pseudorca crassidens

Diel changes in the movement patterns of Ganges River dolphins monitored using stationed stereo acoustic data loggers

Acoustic characteristics of biosonar sounds of free-ranging botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the Negro River, Amazon, Brazil

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