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

Ribak, Gal; Weihs, D.; Arad, Zeev

doi:10.1242/jeb.01856

Cited by 38 publications

(42 citation statements)

References 40 publications

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“…We might expect the effect of gases on buoyancy to match the predictions of our model, with the effect only observed over a relatively narrow range of depths for elephant seals and other deep divers. For shallow divers, however, non-neutral buoyancy may increase the cost of horizontal swimming because of body angle adjustments made to maintain a preferred depth (Ribak et al, 2005). Diving seabirds appear to alter the amount of air carried in their lungs depending on the corresponding depth of the dive Cook et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

Sink fast and swim harder! Round-trip cost-of-transport for buoyant divers

Miller

Biuw

Watanabe

et al. 2012

Journal of Experimental Biology

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SUMMARYEfficient locomotion between prey resources at depth and oxygen at the surface is crucial for breath-hold divers to maximize time spent in the foraging layer, and thereby net energy intake rates. The body density of divers, which changes with body condition, determines the apparent weight (buoyancy) of divers, which may affect round-trip cost-of-transport (COT) between the surface and depth. We evaluated alternative predictions from external-work and actuator-disc theory of how non-neutral buoyancy affects round-trip COT to depth, and the minimum COT speed for steady-state vertical transit. Not surprisingly, the models predict that one-way COT decreases (increases) when buoyancy aids (hinders) one-way transit. At extreme deviations from neutral buoyancy, gliding at terminal velocity is the minimum COT strategy in the direction aided by buoyancy. In the transit direction hindered by buoyancy, the external-work model predicted that minimum COT speeds would not change at greater deviations from neutral buoyancy, but minimum COT speeds were predicted to increase under the actuator disc model. As previously documented for grey seals, we found that vertical transit rates of 36 elephant seals increased in both directions as body density deviated from neutral buoyancy, indicating that actuator disc theory may more closely predict the power requirements of divers affected by gravity than an external work model. For both models, minor deviations from neutral buoyancy did not affect minimum COT speed or round-trip COT itself. However, at body-density extremes, both models predict that savings in the aided direction do not fully offset the increased COT imposed by the greater thrusting required in the hindered direction. Supplementary material available online at

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Section: Discussionmentioning

confidence: 99%

Sink fast and swim harder! Round-trip cost-of-transport for buoyant divers

Miller

Biuw

Watanabe

et al. 2012

Journal of Experimental Biology

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“…where k is the induced power factor (k=1.2) (Pennycuick, 2008), g is acceleration due to gravity (g=9.816 m s −2 ) at mean sea level at the study site (latitude 56 deg) (Pennycuick, 2008), ρ is air density (ρ=1.226 kg m −3 ) (Pennycuick, 2008), b is wing span, S b is frontal body area and C Db is body drag coefficient (C Db =0.28) (Ribak et al, 2005). In contrast, Norberg's model considers that profile power is dependent on air speed, and calculates V mp and V mr using the following equations:…”

Section: Flight Modelsmentioning

confidence: 99%

European shags optimize their flight behavior according to wind conditions

Kogure

Sato

Watanuki

et al. 2016

Journal of Experimental Biology

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Aerodynamics results in two characteristic speeds of flying birds: the minimum power speed and the maximum range speed. The minimum power speed requires the lowest rate of energy expenditure per unit time to stay airborne and the maximum range speed maximizes air distance traveled per unit of energy consumed. Therefore, if birds aim to minimize the cost of transport under a range of wind conditions, they are predicted to fly at the maximum range speed. Furthermore, take-off is predicted to be strongly affected by wind speed and direction. To investigate the effect of wind conditions on take-off and cruising flight behavior, we equipped 14 European shags Phalacrocorax aristotelis with a back-mounted GPS logger to measure position and hence ground speed, and a neck-mounted accelerometer to record wing beat frequency and strength. Local wind conditions were recorded during the deployment period. Shags always took off into the wind regardless of their intended destination and take-off duration was correlated negatively with wind speed. We combined ground speed and direction during the cruising phase with wind speed and direction to estimate air speed and direction. Whilst ground speed was highly variable, air speed was comparatively stable, although it increased significantly during strong head winds, because of stronger wing beats. The increased air speeds in head winds suggest that birds fly at the maximum range speed, not at the minimum power speed. Our study demonstrates that European shags actively adjust their flight behavior to utilize wind power to minimize the costs of take-off and cruising flight.

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“…The model assumes that once the costs of countering buoyancy have been accounted for, the power required to produce any further speed remains the same across dive depths. This may not be valid if, for example, energy savings from swimming patterns such as the burst-and-glide gait (Ribak et al 2005) vary with dive depth. Indeed this is quite likely, given that the burst-and-glide gait appears to provide energy savings during swimming at elevated body angles, and body angle varies with dive depth (Watanuki et al 2005).…”

Section: Model Criticismmentioning

confidence: 99%