Propagation of beluga echolocation signals

Au, Whitlow W. L.; Penner, Ralph H.; Turl, Charles W.

doi:10.1121/1.395278

Cited by 98 publications

(44 citation statements)

References 5 publications

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“…Although this contrasts with general biosonar theory in which target echoes are assumed to be received before emission of the next click (Au, 1993), there is evidence that some toothed whales will solve echolocation tasks with ICIs shorter than the TWTT. Such observations have been made for a beluga whale (Au et al, 1987;Turl and Penner, 1989) and in a phantom-echo study showing that three bottlenose dolphins, including SAY and TRO, increasingly used ICIs below the TWTT when target ranges increased from ∼25 to 100 m (Finneran, 2013). In these studies, the tasks were either to report target presence or absence or the detection of a change in the echo, which is similar to the task that SAY performed in the present study.…”

Section: Long-range (>100 M) Echolocation Involves Click Packetssupporting

confidence: 76%

Dolphin echolocation behaviour during active long-range target approaches

Ladegaard

Mulsow

Houser

et al. 2018

Journal of Experimental Biology

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Echolocating toothed whales generally adjust click intensity and rate according to target range to ensure that echoes from targets of interest arrive before a subsequent click is produced, presumably facilitating range estimation from the delay between clicks and returning echoes. However, this click-echo-click paradigm for the dolphin biosonar is mostly based on experiments with stationary animals echolocating fixed targets at ranges below ∼120 m. Therefore, we trained two bottlenose dolphins instrumented with a sound recording tag to approach a target from ranges up to 400 m and either touch the target (subject TRO) or detect a target orientation change (subject SAY). We show that free-swimming dolphins dynamically increase interclick interval (ICI) out to target ranges of ∼100 m. TRO consistently kept ICIs above the two-way travel time (TWTT) for target ranges shorter than ∼100 m, whereas SAY switched between clicking at ICIs above and below the TWTT for target ranges down to ∼25 m. Source levels changed on average by 17log 10 (target range), but with considerable variation for individual slopes (4.1 standard deviations for by-trial random effects), demonstrating that dolphins do not adopt a fixed automatic gain control matched to target range. At target ranges exceeding ∼100 m, both dolphins frequently switched to click packet production in which interpacket intervals exceeded the TWTT, but ICIs were shorter than the TWTT. We conclude that the click-echo-click paradigm is not a fixed echolocation strategy in dolphins, and we demonstrate the first use of click packets for free-swimming dolphins when solving an echolocation task.

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Section: Long-range (>100 M) Echolocation Involves Click Packetssupporting

confidence: 76%

Dolphin echolocation behaviour during active long-range target approaches

Ladegaard

Mulsow

Houser

et al. 2018

Journal of Experimental Biology

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“…The most directional echolocation signals of smaller toothed whales have been reported for the other species endemic to the Arctic, the beluga [41] having a -3 dB BW of 6.5°. Most other smaller toothed whales emit sonar beams with a -3 dB BW between 8 and 13° [16, 30, 32, 33, 37, 42–44], whereas the largest toothed whale, the sperm whale ( Physeter macrocephalus ) emits signals with a -3 dB BW of 8.3°[45] Recent studies using larger hydrophone arrays and at least in some studies free ranging animals instead of stationary animals have in the harbour porpoise ( Phocoena phocoena ) resulted in higher directionalities as described earlier [33, 34, 37].…”

Section: Discussionmentioning

confidence: 99%

“…Dorso-ventral beam asymmetry has been observed in the harbor porpoise [37], the false killer whale ( Pseudorca crassidens ) [44], bottlenose dolphins ( Tursiops spp.) [48–50] and the beluga [41]. In all species, except the beluga, the beam was narrower above the beam axis than the below the beam axis.…”

Section: Discussionmentioning

confidence: 99%

Highly Directional Sonar Beam of Narwhals (Monodon monoceros) Measured with a Vertical 16 Hydrophone Array

Koblitz¹,

Stilz²,

Rasmussen

et al. 2016

PLoS ONE

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Recordings of narwhal (Monodon monoceros) echolocation signals were made using a linear 16 hydrophone array in the pack ice of Baffin Bay, West Greenland in 2013 at eleven sites. An average -3 dB beam width of 5.0° makes the narwhal click the most directional biosonar signal reported for any species to date. The beam shows a dorsal-ventral asymmetry with a narrower beam above the beam axis. This may be an evolutionary advantage for toothed whales to reduce echoes from the water surface or sea ice surface. Source level measurements show narwhal click intensities of up to 222 dB pp re 1 μPa, with a mean apparent source level of 215 dB pp re 1 μPa. During ascents and descents the narwhals perform scanning in the vertical plane with their sonar beam. This study provides valuable information for reference sonar parameters of narwhals and for the use of acoustic monitoring in the Arctic.

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“…Evolution appears to have favored toothed whales with a high directionality index that seems to be remarkably similar across species [15], with horizontal −3 dB (half-power) beamwidths reported between 13.1 degrees for a harbor porpoise [15] to 6.5 degrees for a beluga ( Delphinapterus leucas ) [62] and 6.2 degrees for a false killer whale ( Pseudorca crassidens ) [63]. Large odontocetes (such as sperm whales or beaked whales) can achieve a certain directionality with lower frequencies than smaller whales (such as porpoises or small delphinids) [37], [63], [64] and this might explain the overall negative correlation between biosonar frequency and body size in toothed whales (Table 2).…”

Section: Discussionmentioning

confidence: 99%

Clicking in Shallow Rivers: Short-Range Echolocation of Irrawaddy and Ganges River Dolphins in a Shallow, Acoustically Complex Habitat

Jensen

Rocco²,

Mansur³

et al. 2013

PLoS ONE

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Toothed whales (Cetacea, odontoceti) use biosonar to navigate their environment and to find and catch prey. All studied toothed whale species have evolved highly directional, high-amplitude ultrasonic clicks suited for long-range echolocation of prey in open water. Little is known about the biosonar signals of toothed whale species inhabiting freshwater habitats such as endangered river dolphins. To address the evolutionary pressures shaping the echolocation signal parameters of non-marine toothed whales, we investigated the biosonar source parameters of Ganges river dolphins (Platanista gangetica gangetica) and Irrawaddy dolphins (Orcaella brevirostris) within the river systems of the Sundarban mangrove forest. Both Ganges and Irrawaddy dolphins produced echolocation clicks with a high repetition rate and low source level compared to marine species. Irrawaddy dolphins, inhabiting coastal and riverine habitats, produced a mean source level of 195 dB (max 203 dB) re 1 µPapp whereas Ganges river dolphins, living exclusively upriver, produced a mean source level of 184 dB (max 191) re 1 µPapp. These source levels are 1–2 orders of magnitude lower than those of similar sized marine delphinids and may reflect an adaptation to a shallow, acoustically complex freshwater habitat with high reverberation and acoustic clutter. The centroid frequency of Ganges river dolphin clicks are an octave lower than predicted from scaling, but with an estimated beamwidth comparable to that of porpoises. The unique bony maxillary crests found in the Platanista forehead may help achieve a higher directionality than expected using clicks nearly an octave lower than similar sized odontocetes.

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Propagation of beluga echolocation signals

Cited by 98 publications

References 5 publications

Dolphin echolocation behaviour during active long-range target approaches

Dolphin echolocation behaviour during active long-range target approaches

Highly Directional Sonar Beam of Narwhals (Monodon monoceros) Measured with a Vertical 16 Hydrophone Array

Clicking in Shallow Rivers: Short-Range Echolocation of Irrawaddy and Ganges River Dolphins in a Shallow, Acoustically Complex Habitat

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