Timing and context of dolphin clicks during and after mine simulator detection and marking in the open ocean

Sam H Ridgway; Dianna S Dibble; Jaime A Kennemer

doi:10.1242/bio.031625

Timing and context of dolphin clicks during and after mine simulator detection and marking in the open ocean

Biol Open. 2018 Feb 20;7(2):bio031625. doi: 10.1242/bio.031625.

Authors

Sam H Ridgway^{1

2}, Dianna S Dibble³, Jaime A Kennemer⁴

Affiliations

¹ Neurobiology Group, National Marine Mammal Foundation, 2240 Shelter Island Drive #200, San Diego, CA 92106, USA sridgway@ucsd.edu.
² Department of Pathology, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
³ Neurobiology Group, National Marine Mammal Foundation, 2240 Shelter Island Drive #200, San Diego, CA 92106, USA.
⁴ U.S. Navy Marine Mammal Program, Space and Naval Warfare Systems Center San Diego 53560 Hull Street, San Diego, CA 92152 , USA.

Abstract

Two dolphins carrying cameras swam in the ocean as they searched for and marked mine simulators - buried, proud or moored. As the animals swam ahead of a boat they searched the ocean. Cameras on their harness recorded continuous sound and video. Once a target was detected, the dolphins received a marker to take to the simulator's location. During search and detection, dolphins made almost continuous trains of varying interval clicks. During the marking phase, shorter click trains were interrupted by periods of silence. As the dolphins marked simulators, they often produced victory squeals - pulse bursts that vary in duration, peak frequency and amplitude. Victory squeals were produced on 72% of marks. Sometimes after marking, or at other times during their long swims, the dolphins produced click packets. Packets typically consisted of two to 10 clicks with inter-click intervals of 7-117 ms followed by a silence of 223-983 ms. Click packets appeared unrelated with searching or marking. We suggest that the packets were used to improve signal to noise ratios for locating a boat or other distant object. Victory squeals produced when marking the targets suggest to us that the dolphins know when they have succeeded in this multipart task.

Keywords: Cameras; Click packets; Clicks; Dolphin; Mine simulators; Victory squeal.