Journal
JOURNAL OF EXPERIMENTAL BIOLOGY
Volume 218, Issue 9, Pages 1314-1324Publisher
COMPANY OF BIOLOGISTS LTD
DOI: 10.1242/jeb.116285
Keywords
Echolocation; Directionality; Biosonar; Perception; Toothed whales; Prey capture
Categories
Funding
- Danish Natural Science Foundation
- La Laguna University
- Woods Hole Oceanographic Institution
- Danish Council for Independent Research \ Natural Sciences
- Carlsberg Foundation
- Natural Environment Research Council [smru10001] Funding Source: researchfish
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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 beam width. We recorded echolocation clicks using a linear array of receivers and estimated the beam width of individual clicks using a parametric spectral fit, cross-validated with well-established composite beam pattern estimates. The dolphins apparently increased the biosonar beam width, 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 viewat 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.
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