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?<https://asa.scitation.org/doi/10.1121/10.0003357> 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<https://marinebioacoustics.wordpress.com/publications/>. Kindest regards, Chloe Chloe Malinka, PhD Fellow Marine Bioacoustics Lab<http://www.marinebioacoustics.com/> . Zoophysiology, Dept. Biology Aarhus University C.F. Møllers Allé 3, Building 1131 DK-8000 Aarhus C, Denmark . Email: chloe.e.malinka@bios.au.dk<mailto:chloe.e.malinka@bios.au.dk> Twitter: @c_malinka<https://twitter.com/c_malinka> [AU_Logo]
