Chapter

Animal Sonar Systems

Volume 28 of the series NATO Advanced Study Institutes Series pp 291-297

Click Sounds from Animals at Sea

  • William A. WatkinsAffiliated withWoods Hole Oceanographic Institution

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Abstract

Echolocation signals from passing cetaceans (Deliphinidae, Phocoenidae, etc.) at sea generally exhibit somewhat different characteristics from those of the same species in captivity that are involved in discrimination experiments in echolocation. Presumably, these differences are partly because the echolocation task at sea would have been primarily for orientation (as suggested by Norris, Evans, and Turner 1967; Norris 1969). Generally, the clicks from groups of cetaceans passing within a few meters of a hydrophone at sea are (1) relatively low frequency (rarely energy above 50 kHz from any species), (2) mostly low level, and (3) often at slow, variable repetition rates. Under these circumstances, the clicks may be used primarily in social contexts.