title: Acoustic behavior of melon-headed whales varies on a diel cycle.
abstract: Many terrestrial and marine species have a diel activity pattern, and their acoustic signaling follows their current behavioral state. Whistles and echolocation clicks on long-term recordings produced by melon-headed whales (Peponocephala electra) at Palmyra Atoll indicated that these signals were used selectively during different phases of the day, strengthening the idea of nighttime foraging and daytime resting with afternoon socializing for this species. Spectral features of their echolocation clicks changed from day to night, shifting the median center frequency up. Additionally, click received levels increased with increasing ambient noise during both day and night. Ambient noise over a wide frequency band was on average higher at night. The diel adjustment of click features might be a reaction to acoustic masking caused by these nighttime sounds. Similar adaptations have been documented for numerous taxa in response to noise. Or it could be, unrelated, an increase in biosonar source levels and with it a shift in center frequency to enhance detection distances during foraging at night. Call modifications in intensity, directionality, frequency, and duration according to echolocation task are well established for bats. This finding indicates that melon-headed whales have flexibility in their acoustic behavior, and they collectively and repeatedly adapt their signals from day- to nighttime circumstances.
authors: Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr. #0205, La Jolla, CA 92093 USA.
authors: Simone
authors: S
authors: Baumann-Pickering
authors: Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr. #0205, La Jolla, CA 92093 USA ; Department of Computer Science, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-7720 USA.
authors: Marie A
authors: MA
authors: Roch
authors: Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr. #0205, La Jolla, CA 92093 USA.
authors: Sean M
authors: SM
authors: Wiggins
authors: Animal Physiology, Institute for Neurobiology, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
authors: Hans-Ulrich
authors: HU
authors: Schnitzler
authors: Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr. #0205, La Jolla, CA 92093 USA.
authors: John A
authors: JA
authors: Hildebrand
keywords: Adaptive acoustic behavior; Ambient noise; Diel pattern; Echolocation; Melon-headed whale