Diel variation in beaked whale diving behavior
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Authors
Baird, Robin
Webster, Daniel L.
Schorr, Gregory S.
McSweeney, Daniel J.
Subjects
Blainville's beaked whale
Whales
Whales
Advisors
Date of Issue
2008
Date
2008
Publisher
Monterey, California. Naval Postgraduate School
Language
Abstract
Diel variation in beaked whale diving behavior is investigated using data from time-depth recorders deployed on six Blainville's (Mesoplodon densirostris) and two Cuvier's (Ziphius cavirostris) beaked whales. Deep foraging dives (>800 m) occurred at similar rates during the day and night for Blainville's beaked whales (daymean=0.38 h-1;nightmean=0.46 h-1), and there were no significant diel differences in depths, durations, ascent or descent rates for deep dives. Dives to mid-water depths (100-600 m) occurred significantly more often during the day (mean=1.59 h-1) than at night (mean=0.26 h-1). Series of progressively shallower bounce dives were only documented following deep, long dives made during the day, while at night whales spent more time in shallow (<100 m) depths. Significantly slower ascent than descent rates were found following deep foraging dives both during the day and night. Similar patterns were found for the Cuvier's beaked whales. These results suggest that so-called bounce dives do not serve a physiological function, although the slow ascents may. This diel variation in behavior suggests that beaked whales may spend less time in surface waters during the day to avoid near-surface, visually-oriented predators, such as large sharks or killer whales (Orcinus orca).
Type
Technical Report
Description
Series/Report No
Department
Organization
Graduate School of Engineering and Applied Science (GSEAS)
CNO/N45 (U.S.)
Identifiers
NPS Report Number
NPS-OC-08-001
Sponsors
Funder
N6227106MPRR403.
Format
ii, 24 p.: ill.28 cm.
Citation
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.