title: Stereotypical rapid source level regulation in the harbour porpoise biosonar.
abstract: Some odontocetes and bats vary both click intensity and receiver sensitivity during echolocation, depending on target range. It is not known how this so-called automatic gain control is regulated by the animal. The source level of consecutive echolocation clicks from a harbour porpoise was measured with a hydrophone array while the animal detected an aluminium cylinder at 2, 4 or 8 m distance in a go/no-go paradigm. On-axis clicks had source levels of 145-174 dB re 1 μPa peak-to-peak. During target-present trials the click trains reached comparable source levels independent of the range to the target after three clicks. After an additional click, the source level was reduced for the 2 and 4 m trials until it equalled the one-way transmission loss. During target-absent trials, the source level remained high throughout the entire click train. Given typical values of harbour porpoise inter-click intervals, the source level reduction commenced within a few 100 ms from the first click in the click train. This may indicate a sub-cortically regulated source level regulation in the harbour porpoise.
authors: Institute of Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark. meike@biology.sdu.dk
authors: Meike
authors: M
authors: Linnenschmidt
authors: Laura N
authors: LN
authors: Kloepper
authors: Magnus
authors: M
authors: Wahlberg
authors: Paul E
authors: PE
authors: Nachtigall
mesh_terms: D000818:Animals; D004455:Echolocation / Q000502:physiology; D050741:Phocoena / Q000502:physiology*; D014828:Vocalization, Animal / Q000502:physiology*