QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online February 6, 2004
Journal of Experimental Biology 207, 973-982 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00822

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JEB Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Williams, T. M. Articles by Davis, R. W. Search for Related Content PubMed PubMed Citation Articles by Williams, T. M. Articles by Davis, R. W.

The cost of foraging by a marine predator, the Weddell seal Leptonychotes weddellii: pricing by the stroke

Terrie M. Williams^1,*, Lee A. Fuiman², Markus Horning³ and Randall W. Davis³

¹ Department of Ecology and Evolutionary Biology, Center for Ocean Health, Long Marine Laboratory, 100 Shaffer Road, University of California at Santa Cruz, Santa Cruz, CA 95060, USA
² University of Texas at Austin, Department of Marine Science, Marine Science Institute, 750 Channel View Drive, Port Aransas, Texas 78373, USA
³ Department of Marine Biology, Texas A&M University at Galveston, 5007 Avenue U, Galveston, TX 77553 USA

View larger version (15K): [in a new window]   Fig. 1. Post-dive oxygen consumption in relation to dive duration for Weddell seals diving with (closed circles) and without (open circles) the video-data logging system. Each point represents an individual dive. No statistical difference was found in oxygen consumption between the groups (see text), although uninstrumented seals tended to perform the longest dives.

View larger version (15K): [in a new window]   Fig. 2. Changes in plasma lactate concentration (A), recovery oxygen consumed (B) and post-dive oxygen consumption rate (C) in relation to dive duration for nine adult Weddell seals. Measurements were taken during the recovery period immediately following each dive. Points represent individual dives for an animal. The dashed vertical line denotes the change from aerobic to anaerobic dives, as indicated by the increase in plasma [lactate] above resting levels. Equations for statistical relationships are provided in the text.

View larger version (15K): [in a new window]   Fig. 3. Residuals for recovery oxygen consumption of a foraging Weddell seal. Data are presented in relation to time following first fish ingestion in a feeding bout. The final five dives of a sequence consisting of 11 foraging dives are shown. Each point represents the residual for the recovery period following a dive. Fish indicate times when we observed the seal eating Pleuragramma antarcticum. 44 fish were ingested at the beginning of this bout, with one additional fish caught on the tenth dive of the sequence. Residuals were determined by comparing the observed post-dive recovery oxygen consumption to predicted values based on Fig. 2B and Equation 3.

View larger version (22K): [in a new window]   Fig. 4. Recovery oxygen consumption of feeding (post-prandial) and fasting (post-absorptive) dives in free-ranging Weddell seals. Each point represents a feeding dive paired with a fasting dive of equal distance traveled (within 6.8±1.7%) and duration (within 8.3±1.7%) for two male seals of identical body mass (398 kg). The diagonal line through the origin represents the line of equality for the cost of feeding and fasting dives. The short line denotes the least-squares linear regression through the data points, as described in the text.

View larger version (19K): [in a new window]   Fig. 5. Recovery oxygen consumed (A) and locomotor costs (B) of diving Weddell seals in relation to the total number of strokes taken during a dive. Measurements were taken during the post-dive recovery period. Points represent individual dives. Solid lines are the least squares linear regressions through the data points as described in the text. Note that only aerobic dives, as determined from Fig. 2 were used in these analyses.

View larger version (15K): [in a new window]   Fig. 6. The effects of behavior on recovery oxygen consumption in diving Weddell seals. Each point represents an individual dive for an animal as shown in Fig. 2B, now color coded for feeding behavior as determined from video sequences, and aerobic limits determined from blood [lactate] values. Aerobic and anaerobic dives for non-foraging seals are shown in black and dark blue circles, respectively. Post-dive oxygen consumption increased in foraging seals, and is indicated by red (aerobic dives) and light blue (anaerobic dives) circles.

View larger version (13K): [in a new window]   Fig. 7. Total cost of a stroke or stride in relation to body mass for swimming phocid seals and running mammals. Each point represents the mean stroke costs calculated from the oxygen consumption and stroke frequency of harbor (Davis et al., 1985), and gray, ringed and harp (Innes, 1984; Fish et al., 1988) seals swimming in a flume. Weddell seal data are from the present study. The solid line is the mean total cost per stroke for five species of swimming phocid seal. The dashed line is the mean cost per stride for running terrestrial mammals from Taylor et al. (1982).