Nighttime foraging by deep diving echolocating odontocetes off the Hawaiian islands of Kauai and Ni'ihau as determined by passive acoustic monitors

TitleNighttime foraging by deep diving echolocating odontocetes off the Hawaiian islands of Kauai and Ni'ihau as determined by passive acoustic monitors
Publication TypeJournal Article
Year of Publication2013
AuthorsAu, Whitlow W. L., Giorli Giacomo, Chen Jessica, Copeland Adrienne, Lammers Marc, Richlen Michael, Jarvis Susan, Morrisey Ronald, Moretti David, and Klinck Holger
JournalThe Journal of the Acoustical Society of America
Volume133
Pagination3119-3127
EndNote Rec Number10225
Abstract

Remote autonomous ecological acoustic recorders (EARs) were deployed in deep waters at five locations around the island of Kauai and one in waters off Ni'ihau in the main Hawaiian island chain. The EARs were moored to the bottom at depths between 400 and 800m. The data acquisition sampling rate was 8 kHz and acoustic signals were recorded for 30s every 5min to conserve battery power and disk space. The acoustic data were analyzed with the M3R (Marine Mammal Monitoring on Navy Ranges) software, an energy-ratio-mapping algorithm developed at Oregon State University and custom MATLAB programs. A variety of deep diving odontocetes, including pilot whales, Risso's dolphins, sperm whales, spinner and pan-tropical spotted dolphins, and beaked whales were detected at all sites. Foraging activity typically began to increase after dusk, peaked in the middle of the night and began to decrease toward dawn. Between 70% and 84% of biosonar clicks were detected at night. At present it is not clear why some of the known deep diving species, such as sperm whales and beaked whales, concentrate their foraging efforts at night.