title: Single-click beam patterns suggest dynamic changes to the field of view of echolocating Atlantic spotted dolphins (Stenella frontalis) in the wild.
abstract: 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 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.
authors.affiliation: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08540, USA Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA frants.jensen@gmail.com.
authors.forename: Frants H
authors.initials: FH
authors.lastname: Jensen
authors.affiliation: Fjord & Bælt, Margrethes Plads 1, Kerteminde 5300, Denmark Marine Biological Research Center, University of Southern Denmark, Hindsholmsvej 11, Kerteminde 5300, Denmark.
authors.forename: Magnus
authors.initials: M
authors.lastname: Wahlberg
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, Aarhus 8000, Denmark.
authors.forename: Kristian
authors.initials: K
authors.lastname: Beedholm
authors.affiliation: Scottish Oceans Institute, University of St Andrews, Fife KY16 8LB, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Johnson
authors.affiliation: Scottish Oceans Institute, University of St Andrews, Fife KY16 8LB, UK BIOECOMAC, Department of Animal Biology, International Campus of Excellence, La Laguna University, La Laguna, Tenerife 38206, Spain.
authors.forename: Natacha Aguilar
authors.initials: NA
authors.lastname: de Soto
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, Aarhus 8000, Denmark Murdoch University Cetacean Research Unit, School of Veterinary and Life Sciences, Murdoch University, South Street, Murdoch, Western Australia 6150, Australia.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Madsen
mesh_terms: D000818:Animals; D004455:Echolocation; D011235:Predatory Behavior; D013018:Sound Spectrography; D050706:Stenella / Q000502:physiology*
keywords: Biosonar; Directionality; Echolocation; Perception; Prey capture; Toothed whales