The auditory time resolution in bottlenose dolphins: Behavioral experiments versus auditory evoked potential methods

Zaslavski, Gennadi L.

doi:10.1121/1.2934831

Cited by 2 publications

(1 citation statement)

References 18 publications

(47 reference statements)

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“…In contrast, much shorter integration times for odontocetes have been proposed (Beedholm and Miller, 2008;Zaslavski, 2012). Specifically, time resolution constants as low as 20 µs have been suggested for Tursiops and 50 µs for harbour porpoises in behavioural experiments involving the discrimination of targets placed near a clutter screen (Zaslavskiy, 2003;Zaslavski, 2008Zaslavski, , 2012. However, owing to different methodological approaches, these results are difficult to reconcile or compare with those converging on ∼264 µs.…”

Section: Auditory Integration Time and Target Resolutionmentioning

confidence: 99%

Directional biosonar beams allow echolocating harbour porpoises to actively discriminate and intercept closely spaced targets

Malinka

Rojano-Doñate

Madsen

2021

Journal of Experimental Biology

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Echolocating toothed whales face the problem that high sound speeds in water mean that echoes from closely-spaced targets will arrive at time delays within their reported auditory integration time of some 264 µsec. Here we test the hypothesis that echolocating harbour porpoises cannot resolve and discriminate targets within a clutter interference zone given by their integration time. To do this, we trained two harbour porpoises (Phocoena phocoena) to actively approach and choose between two spherical targets at four varying inter-target distances (13.5, 27, 56 and 108 cm) in a two-alternative forced-choice task. The free-swimming, blindfolded porpoises were tagged with a sound and movement tag (DTAG4) to record their echoic scene and acoustic outputs. The known ranges between targets and the porpoise, combined with the sound levels received on target-mounted hydrophones revealed how they controlled their acoustic gaze. When targets were close together and the discrimination task was more difficult due to smaller echo time delays and lower echo level ratios between the targets, buzzes were longer and started from farther away, source levels were reduced at short ranges, and the porpoises clicked faster, scanned across the targets more, and delayed making their discrimination decision until closer to the target. We conclude that harbour porpoises can resolve and discriminate closely-spaced targets, suggesting a clutter rejection zone much shorter than their auditory integration time, and that such clutter rejection is greatly aided by spatial filtering with their directional biosonar beam.

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Section: Auditory Integration Time and Target Resolutionmentioning

confidence: 99%

Directional biosonar beams allow echolocating harbour porpoises to actively discriminate and intercept closely spaced targets

Malinka

Rojano-Doñate

Madsen

2021

Journal of Experimental Biology

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Clutter resilience via auditory stream segregation in echolocating greater mouse-eared bats

Pedersen,

Beedholm,

Hubancheva

et al. 2024

Journal of Experimental Biology

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Bats use echolocation to navigate and hunt in darkness, and must in that process segregate target echoes from unwanted clutter echoes. Bats may do this by approaching a target at steep angles relative to the plane of the background, utilizing their directional transmission and receiving systems to minimize clutter from background objects, but it remains unknown how bats negotiate clutter that cannot be spatially avoided. Here, we test the hypothesis that when movement no longer offers spatial release, echolocating bats mitigate clutter by calling at lower source levels and longer call intervals to ease auditory streaming. We trained five greater mouse-eared bats (Myotis myotis) to land on a spherical loudspeaker with two microphones attached. We used a phantom-echo setup, where the loudspeaker/target transmitted phantom clutter echoes by playing back the bats’ own calls at time-delays of 1, 3 and 5 milliseconds with a virtual target strength 7 dB higher than the physical target. We show that the bats successfully landed on the target, irrespective of the clutter echo-delays. Rather than decreasing their source levels, the bats used similar source level distributions in clutter-, and control-trials. Similarly, the bats did not increase their call intervals, but instead used the same distribution of call intervals across control-, and clutter-trials. These observations reject our hypothesis, leading us to conclude that bats display great resilience to clutter via short auditory integration times and acute auditory stream segregation rather than via biosonar adjustments.

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The auditory time resolution in bottlenose dolphins: Behavioral experiments versus auditory evoked potential methods

Cited by 2 publications

References 18 publications

Directional biosonar beams allow echolocating harbour porpoises to actively discriminate and intercept closely spaced targets

Directional biosonar beams allow echolocating harbour porpoises to actively discriminate and intercept closely spaced targets

Clutter resilience via auditory stream segregation in echolocating greater mouse-eared bats

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