Acoustic gaze adjustments during active target selection in echolocating porpoises

Danuta Maria Wisniewska*, Mark Johnson, Kristian Beedholm, Magnus Wahlberg, Peter Teglberg Madsen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Citations (Scopus)

Abstract

Visually dominant animals use gaze adjustments to organize perceptual inputs for cognitive processing. Thereby they manage the massive sensory load from complex and noisy scenes. Echolocation, as an active sensory system, may provide more opportunities to control such information flow by adjusting the properties of the sound source. However, most studies of toothed whale echolocation have involved stationed animals in static auditory scenes for which dynamic information control is unnecessary. To mimic conditions in the wild, we designed an experiment with captive, free-swimming harbor porpoises tasked with discriminating between two hydrophone-equipped targets and closing in on the selected target; this allowed us to gain insight into how porpoises adjust their acoustic gaze in a multi-target dynamic scene. By means of synchronized cameras, an acoustic tag and on-target hydrophone recordings we demonstrate that porpoises employ both beam direction control and range-dependent changes in output levels and pulse intervals to accommodate their changing spatial relationship with objects of immediate interest. We further show that, when switching attention to another target, porpoises can set their depth of gaze accurately for the new target location. In combination, these observations imply that porpoises exert precise vocal-motor control that is tied to spatial perception akin to visual accommodation. Finally, we demonstrate that at short target ranges porpoises narrow their depth of gaze dramatically by adjusting their output so as to focus on a single target. This suggests that echolocating porpoises switch from a deliberative mode of sensorimotor operation to a reactive mode when they are close to a target.

Original languageEnglish
Pages (from-to)4358-4373
Number of pages16
JournalJournal of Experimental Biology
Volume215
Issue number24
Early online date21 Nov 2012
DOIs
Publication statusPublished - Dec 2012

Keywords

  • echolocation
  • acoustic gaze control
  • scanning
  • toothed whale
  • porpoise

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