Dear MARMAM community,
We’d like to let you know about a new publication in JASA where we re-evaluate optimal localization hypothesis as an echolocation strategy used by odontocetes:
Beedholm, K., Malinka, C., Ladegaard, M., and P. T. Madsen. (2021).
Do echolocating toothed whales direct their acoustic gaze on- or off-target in a static detection task?
The Journal of the Acoustical Society of America 149, 581-590.
Abstract: Echolocating mammals produce directional sound beams with high source levels to improve echo-to-noise ratios and reduce clutter. Recent studies have suggested that the differential spectral gradients of such narrow beams
are exploited to facilitate target localization by pointing the beam slightly off targets to maximize the precision of angular position estimates [maximizing bearing Fisher information (FI)]. Here, we test the hypothesis that echolocating toothed whales focus
their acoustic gaze askew during target detection to maximize spectral cues by investigating the acoustic gaze direction of two trained delphinids (Tursiops truncatus
and Pseudorca crassidens) echolocating to detect an aluminum cylinder behind a hydrophone array in a go/no-go paradigm. The animals rarely placed their beam axis directly on the target, nor within the narrow range around the off-axis angle that maximizes
FI. However, the target was, for each trial, ensonified within the swath of the half-power beam width, and hence we conclude that the animals solved the detection task using a strategy that seeks to render high echo-to-noise ratios rather than maximizing bearing
FI. We posit that biosonar beam adjustment and acoustic gaze strategies are likely task-dependent and that maximizing bearing FI by pointing off-axis does not improve target detection performance.
The PDF is also available on the
Bioacoustics Aarhus lab website.
Kindest regards,
Chloe
Chloe Malinka, PhD Fellow
.
Zoophysiology, Dept. Biology
Aarhus University
C.F. Møllers Allé 3, Building 1131
DK-8000 Aarhus C, Denmark
.
Email:
chloe.e.malinka@bios.au.dk
Twitter: @c_malinka
