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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 54 (2007): 1421-1444, doi:10.1016/j.dsr.2007.04.020.
    Description: Toothed whales produce short, ultrasonic clicks of high directionality and source level to probe their environment acoustically. This process, termed echolocation, is to a large part governed by the properties of the emitted clicks. Therefore derivation of click source parameters from free-ranging animals is of increasing importance to understand both how toothed whales use echolocation in the wild and how they may be monitored acoustically. This paper addresses how source parameters can be derived from free-ranging toothed whales in the wild using calibrated multi-hydrophone arrays and digital recorders. We outline the properties required of hydrophones, amplifiers and analog to digital converters, and discuss the problems of recording echolocation clicks on the axis of a directional sound beam. For accurate localization the hydrophone array apertures must be adapted and scaled to the behavior of, and the range to, the clicking animal, and precise information on hydrophone locations is critical. We provide examples of localization routines and outline sources of error that lead to uncertainties in localizing clicking animals in time and space. Furthermore we explore approaches to time series analysis of discrete versions of toothed whale clicks that are meaningful in a biosonar context.
    Description: This work was supported by a Steno Fellowship from the Danish National Science Foundation to PTM, a grant from the Carlsberg Foundation to MW with additional support to the authors from Reson, the Novo Nordisk Science Foundation, Aarhus University Research Fund, and the Oticon Foundation.
    Keywords: Toothed whale ; Ultrasound ; Recording ; Click ; Hydrophone ; Array ; Echolocation
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
    Location Call Number Limitation Availability
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © The Company of Biologists, 2015. This is the author's version of the work. It is posted here by permission of Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology (2015), doi:10.1242/​jeb.116285.
    Description: Echolocating animals exercise an extensive control over the spectral and temporal properties of their biosonar signals to facilitate perception of their actively generated auditory scene when homing in on prey. The intensity and directionality of the biosonar beam defines the field of view of echolocating animals by affecting the acoustic detection range and angular coverage. However, the spatial relationship between an echolocating predator and its prey changes rapidly, resulting in different biosonar requirements throughout prey pursuit and capture. Here we measured single click beam patterns using a parametric fit procedure to test whether free-ranging Atlantic spotted dolphins (Stenella frontalis) modify their biosonar beamwidth. We recorded echolocation clicks using a linear array of receivers and estimated the beamwidth of individual clicks using a parametric spectral fit, cross-validated with well-established composite beam pattern estimates. The dolphins apparently increased the biosonar beamwidth, to a large degree without changing the signal frequency, when they approached the recording array. This is comparable to bats that also expand their field of view during prey capture, but achieve this by decreasing biosonar frequency. This behaviour may serve to decrease the risk that rapid escape movements of prey take them outside the biosonar beam of the predator. It is likely that shared sensory requirements have resulted in bats and toothed whales expanding their acoustic field of view at close range to increase the likelihood of successfully acquiring prey using echolocation, representing a case of convergent evolution of echolocation behaviour between these two taxa.
    Description: The study was funded by frame grants from the Danish Natural Science Foundation to PTM and MW, and by the National Oceanographic Partnership Programme via a research agreement between La Laguna University (NAS) and the Woods Hole Oceanographic Institution (MJ). FHJ was supported by the Danish Council for Independent Research | Natural Sciences, and is currently funded by a postdoctoral fellowship from the Carlsberg Foundation.
    Description: 2016-03-12
    Keywords: Echolocation ; Directionality ; Field of view ; Perception ; Dolphin ; Prey capture
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
    Location Call Number Limitation Availability
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