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Acoustic behavior of melon-headed whales varies on a diel cycle

A distinct shift in echolocation behavior from day to night.
TitleAcoustic behavior of melon-headed whales varies on a diel cycle
Publication TypeJournal Article
Year of Publication2015
AuthorsBaumann-Pickering S., Roch M.A, Wiggins SM, Schnitzler H.U, Hildebrand JA
JournalBehavioral Ecology and Sociobiology
Date Published2015/09
Type of ArticleArticle
ISBN Number0340-5443
Accession NumberWOS:000359639500015
KeywordsAdaptive acoustic behavior; ambient noise; amplitude regulation; Diel pattern; dolphins tursiops-truncatus; echolocation; echolocation clicks; environmental noise; harbor porpoises; lagenorhynchus-obscurus; Melon-headed; peponocephala-electra; southern california bight; spinner dolphins; stenella-longirostris; whale

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.

Short TitleBehav. Ecol. Sociobiol.

A long-term, collective diel adaptation in free-ranging odontocetes’ biosonar source levels and spectral content either as an adjustment for larger detection distances of prey or to overcome diel changes in ambient sound was discussed. The results show that in the field, just as in captivity, the structure of echolocation clicks is not a rigid entity but changes in response to environmental or situational stimuli.

Future research should test further in the field, how echolocation click structures are modified as a result of increased detection range, as animals change their focal behavior from navigation to foraging, and in the presence of natural or anthropogenic noise. In relation to adjustments due to noise, it seems relevant at what point masking is becoming a disadvantage for equal foraging success and what effect additional energy expenditure due to prolonged foraging has on the ecology of echolocating species.

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