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First published online November 14, 2008
Journal of Experimental Biology 211, 3712-3719 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.023366
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Foraging behavior of humpback whales: kinematic and respiratory patterns suggest a high cost for a lunge

Jeremy A. Goldbogen1,*, John Calambokidis2, Donald A. Croll3, James T. Harvey4, Kelly M. Newton3, Erin M. Oleson5, Greg Schorr2 and Robert E. Shadwick1

1 Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4
2 Cascadia Research Collective, 218.5 W. 4th Avenue, Olympia, WA 98501, USA
3 Department of Ecology and Evolutionary Biology, Center for Ocean Health, 100 Shaffer Road, University of California, Santa Cruz, CA 95060, USA
4 Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA
5 Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA


Figure 1
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  		Fig. 1. A tagged humpback whale. The bioacoustic probe was equipped with silicon suction cups for attachment and a floatation device to facilitate recovery.

 

Figure 2
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  		Fig. 2. Flow noise increases with body speed. The relationship between flow noise, measured by the hydrophone, and speed, calculated from the kinematics of the body, is shown for each whale (MnA, gray; MnB, black) during steep glides (–30 deg.≥pitch≥30 deg.). The relationship between flow noise and body speed was consistent among whales; each line represents a quadratic regression through the data from each whale (MnA, r2=0.76; MnB, r2=0.84).

 

Figure 3
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  		Fig. 3. Detection of breaths during a surface interval. We interpreted the cyclic kinematic (bottom panel) and repeatable acoustic (top two panels) patterns during surface intervals as a series of breaths. As the tag breaks the surface, a signal was evident in both the waveform (middle panel) and spectrogram (top panel). These events (marked by dashed red arrows) coincided with minima in the dive profile (gray trace) and were phase coupled with the body pitch record (black lines), such that dive profile minima occurred when the body was level (pitch=0 deg.). Here we show a 3.7 min surface interval with 17 breaths following a foraging dive that included 15 lunges at depth (the dive shown in Fig. 4).

 

Figure 4
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  		Fig. 4. Kinematics of foraging dives. Swimming strokes (acceleration), speed and pitch angle are shown for a foraging dive (whale MnA). Foraging dives consisted of a gliding descent and an ascent powered by steady swimming. Lunges at the bottom of each dive are marked by speed maxima and bouts of fluking. Each lunge is identified by a red arrow and highlights how the deceleration phase of each lunge occurs during continued swimming, which is a defining characteristic of a lunge. The vertical blue line marks a speed maximum that is not considered a lunge because it is associated with the tag breaking the sea surface. Also note how each lunge occurs when the body is approximately horizontal (dashed line).

 

Figure 5
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  		Fig. 5. Dive profiles and vertical distribution of prey. (A) Dive profiles (yellow line) and lunges (green circles) are superimposed onto prey-field maps generated from echosounder data which show increasing density of zooplankton (red, highest; blue, medium; white, lowest) and the sea floor (green line). (B) Relative krill density as a function of depth derived from the nautical area scattering coefficient (m2 target nautical mi–2) integrated every 15 sx10 m along the path of the foraging whale (left graph). The right graph shows the depth distribution where each lunge was executed during the foraging bout. The dashed line shows the mean value for lunge depth. The overlaying grid corresponds to dimensions that are 10 m deep by 1 min long.

 

Figure 6
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  		Fig. 6. Time series of diving behavior. Dive duration (thin black line), maximum dive depth (dashed black line), lunge frequency (thin gray line), and post-dive breaths (dashed gray line) are shown as a function of sequential dive number for whale MnA (A) and MnB (B). Dives 31–49 are shown with hydroacoustic data in Fig. 5 (light blue box).

 

Figure 7
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  		Fig. 7. Respiratory and kinematic parameters associated with lunge frequency. (A) Foraging dives that involved more lunges required longer dive durations (MnA, r2=0.77, P<0.001; MnB, r2=0.65, P<0.001) and (B) more bottom time (MnA, r2=0.83, P<0.001; MnB, r2=0.77, P<0.001). (C) A significant correlation was found between the number of lunges executed per dive and the number of post-dive recovery breaths (MnA, r2=0.83, P<0.001; MnB, r2=0.63, P<0.001). (D) Post-dive surface time increased with lunge frequency (MnA, r2=0.52, P<0.001; MnB, r2=0.43, P<0.001). (E) Lunge frequency was associated with a steeper ascent following the lunge bout (D; MnA, r2=0.73, P<0.001; MnB, r2=0.72, P<0.001) and a steeper descent during the subsequent dive (D; MnA, r2=0.42, P<0.001; MnB, r2=0.66, P<0.001). Black lines, MnB; gray lines, MnA.

 

Figure 8
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  		Fig. 8. Relationship between dive duration and respiration rate for singing and foraging humpbacks. Data for foraging whales are for MnA (gray circles) and MnB (black circles) and data for four singing humpback whales are shown as open symbols (Chu, 1988Go). Dive duration increased with the number of breaths taken after that dive (MnA, y=5.450–0.409x+0.155x2), r2=0.77, P<0.001; MnB, y=4.085–0.908x+0.207x2, r2=0.62, P=0.005). Note that the longest singing dives (20 min) are approximately twice as long as the longest foraging dives (10 min). Also, at dive durations of 10 min, the number of breaths taken is three times higher during foraging.

 

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© The Company of Biologists Ltd 2008