Listening to Hawaiian Spinner Porpoises, Stenella cf. Longirostris, with a Three-Dimensional Hydrophone Array

Abstract

A three-dimensional array of hydrophones was anchored for 6 days (8 to 13 May 1971) in Kealakekua Bay on the island of Hawaii in order to listen to the underwater sounds of a resident population of spinner porpoises, Stenella cf. longirostris (Gray, 1828). Arrival-times for individual porpoise sounds were measured, and source locations were calculated to provide a three-dimensional indication of position for calling animals. Most sounds originated at depths less than 10 meters, and many of them were exchanges of sounds by porpoises within 10 to 15 meters of each other. Source level calculations indicated a wide range of levels that suggest intentional control of sound level. The three-dimensional array provided information that would not have been available by single hydrophone listening.