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

First published online October 7, 2005
Journal of Experimental Biology 208, 3835-3849 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01856

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 Ribak, G. Articles by Arad, Z. Search for Related Content PubMed PubMed Citation Articles by Ribak, G. Articles by Arad, Z. Social Bookmarking                         What's this?

Submerged swimming of the great cormorant Phalacrocorax carbo sinensis is a variant of the burst-and-glide gait

Gal Ribak¹, Daniel Weihs^2,* and Zeev Arad¹

¹ Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
² Faculty of Aerospace Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel

View larger version (23K): [in a new window]   Fig. 1. Shape of the cormorant's body in three dimensions. (A) Schematic illustration (not to scale) of the apparatus used to measure the diameters of the cormorant carcass along the body's main axis.(B) Diameter of the width (lateral axis, solid rectangles) and height (dorso–ventral axis, empty circles). The x-axis represents the position along the body's main axis in % of body length (total body length = 85 cm). The diameters were used to calculate surface area, volume and added mass coefficients. The broken vertical lines mark the definition of the body excluding the neck and tail (trunk).

View larger version (18K): [in a new window]   Fig. 2. Variation in velocity during one paddling cycle. The plot was obtained from one video sequence (Bird 5) and smoothed by a stepwise 5-point moving average for easy viewing. The plot shows the kinematic parameters defined by Weihs (1974) for the burst-and-glide model (L1, L2, Ui, Uf), and the additional parameters defined in the present study (Lp, Lg, Lr, Ur, tp, tg, tr); see List of symbols for the description of each parameter. The bottom bar indicates the division of the paddling cycle into three stages based on the motion of the feet relative to the body (stroke, glide and recovery). Average swimming speed for this cycle was 1.72 m s–1. Note that the bird did not swim at a constant speed but rather accelerated during the power stage and decelerated during the glide and recovery stages in a burst-and-glide swimming pattern.

View larger version (7K): [in a new window]   Fig. 3. The average swimming speed observed for each cormorant in the experiment relative to body length. Each point is the mean swimming speed obtained from 5–10 sequences taken of the same bird (values are ± S.E.M.).

View larger version (18K): [in a new window]   Fig. 4. The duration of each stage in the paddling cycle of the great cormorant (A) and the proportion of the power (burst) and deceleration (glide + recovery) stages in the paddling cycle (B) in relation to paddling frequency. Note that the glide duration decreased with the increase in paddling frequency. At a paddling frequency of 2.7 Hz, the duration of the glide phase was diminished to almost zero so that the power and recovery stages each occupy 50% of the paddling cycle duration.

View larger version (18K): [in a new window]   Fig. 5. The distribution of the momentary drag along an average paddling cycle of the great cormorant. Momentary drag is calculated using the Cd average for each of the paddling stages. To average all the analyzed sequences despite the differences in cycle duration, the x-axis is the proportion of the cycle duration that is normalized by dividing the period of each stage (stroke, glide and recovery) by the mean duration of that stage. To allocate equal weight to all birds, the sequences of each bird were first averaged and then means ± S.E.M. of all birds were calculated.

View larger version (16K): [in a new window]   Fig. 6. The `burst-and-glide' parameters R or Rp (A) and (B) in relation to the average swimming speed of the great cormorant in each paddling cycle. Open symbols denote calculated values when the recovery is treated as part of the burst stage and full symbols are calculated values when the recovery is treated as part of the glide stage (see text). Solid horizontal lines mark the proportion of 1, where the energetic cost of burst-and-glide is exactly the same as for swimming at constant speed. Broken vertical lines in A mark the threshold average speed where the least square regression of the points (broken line for Rp, solid line for R) intersects with the value of 1. At this swimming speed the energetic benefit from burst-and-glide changes from gain (R<1) into loss (R>1). In B, values 1 imply that the drag coefficient for passive drag is as high as or higher than the coefficient for active swimming. Note that the open symbols represent a more conservative approach for estimating the energetic advantage from burst-and-glide.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

Twitter