Patterns of respiration in diving penguins: is the last gasp an inspired tactic?

Abstract

SUMMARYHumboldt penguins Spheniscus humboldti in captivity and free-living Magellanic penguins S. magellanicus were fitted with loggers to determine beak angles during breathing. The Humboldt penguins were also fitted with masks for determining rates of air flow during breathing. During periods of higher gas exchange requirement, Humboldt penguins opened their beaks during inspiration, where tidal volume was linearly correlated with both change in beak angle and maximum beak angle, closed them slightly during the final stages of inspiration and finally closed them during expiration. Substantial differences were apparent between individuals. Contrary to the condition proposed for most birds, our data suggest that expiration is passive during periods of high respiratory tidal volumes, and that the increased resistance of the respiratory pathway serves to slow air flow so as to maximize gas exchange in the lungs. During foraging, Magellanic penguins at the surface between dives showed similar breathing patterns but maximum beak angles were much higher and breath cycle time shorter, as would be expected for animals attempting to maximize gas exchange. Both maximum beak angle per breath and breath frequency changed systematically over the surface pause; both were initially high, then decreased to a low before rising again to a maximum just before diving. Based on known changes in tidal volume with beak angle derived from Humboldt penguins, a simple model is proposed to examine rates of gas exchange over the surface pause. This indicates that the observed patterns do not maximize the rate of transfer of oxygen over the whole of the surface pause but are rather concerned with an initial rapid accumulation of oxygen in the tissues followed by effective carbon dioxide release.

N-dimensional animal energetic niches clarify behavioural options in a variable marine environment

“…Note that the beak is opened while the bird is at the surface for breathing (cf. Wilson et al, 2003) and otherwise opened underwater for prey ingestion (arrows -one prey item is caught in dive 3 and 4 in dive 4). (C)The dives of the bird exemplified in B (black spheres) is shown on a more expansive section of the energy envelope in relation to a series of dives made by two other birds denoted by red and blue spheres, respectively, to show how individuals move over the energetic niche.…”

“…However, the precise amount of air inhaled by penguins as a function of dive depth has not been quantified (cf. Sato et al, 2002;Wilson et al, 2003) so calculated buoyancies at any given depth can be higher during deeper dives than in shallow ones and the energy envelope may change accordingly.…”

“…Although the volume of air in feathers is likely to remain invariant (at constant pressure), there is a suggestion that penguins might inhale more for deeper dives (Sato et al, 2002;Wilson and Zimmer, 2004), although the extent is unknown. Given that penguins always inhale prior to diving (Kooyman, 1975;Wilson et al, 2003), the volume of air in the respiratory system is unlikely to be much less than half that originally proposed by Kooyman (Kooyman, 1975) for 'shallow' dives and much more than half as much again for 'deep' ones (cf. Wilson et al, 2003) (giving a span of 0.16lkg…”

“…Given that penguins always inhale prior to diving (Kooyman, 1975;Wilson et al, 2003), the volume of air in the respiratory system is unlikely to be much less than half that originally proposed by Kooyman (Kooyman, 1975) for 'shallow' dives and much more than half as much again for 'deep' ones (cf. Wilson et al, 2003) (giving a span of 0.16lkg…”

The significance of respiration timing in the energetics estimates of free-ranging killer whales (Orcinus orca)

“…A prolonged apnoea, as occurs during longer dives, causes a larger O 2 storage depletion compared with that from shorter dives. The uptake efficiency increases swiftly for short dives and flattens for longer dives when the maximum possible uptake is approached (Sumich, 1994(Sumich, , 2001Parkes et al, 2002;Wilson et al, 2003;Fahlman et al, 2008). A higher MR, dependent upon activity level, causes the O 2 store to deplete faster than a lower MR.…”