P. J. Butler

Hypothermia in foraging king penguins

The ability to dive for long periods increases with body size, but relative to the best human divers, marine birds and mammals of similar or even smaller size are outstanding performers. Most trained human divers can reach a little over 100 m in a single-breath dive lasting for 4 min (ref. 2), but king and emperor penguins (weighing about 12 and 30 kg, respectively) can dive to depths of 304 and 534 m for as long as 7.5 and 15.8 min, respectively. On the basis of their assumed metabolic rates, up to half of the dive durations were believed to exceed the aerobic dive limit, which is the time of submergence before all the oxygen stored in the body has been used up. But in penguins and many diving mammals, the short surface intervals between dives are not consistent with the recovery times associated with a switch to anaerobic metabolism. We show here that the abdominal temperature of king penguins may fall to as low as 11 °C during sustained deep diving. As these temperatures may be 10 to 20 °C below stomach temperature, cold ingested food cannot be the only cause of abdominal cooling. Thus, the slower metabolism of cooler tissues resulting from physiological adjustments associated with diving per se, could at least partly explain why penguins and possibly marine mammals can dive for such long durations.

A Phylogenetic Analysis of the Allometry of Diving

The oxygen store/usage hypothesis suggests that larger animals are able to dive for longer and hence deeper because oxygen storage scales isometrically with body mass, whereas oxygen usage scales allometrically with an exponent <1 (typically 0.67–0.75). Previous tests of the allometry of diving tend to reject this hypothesis, but they are based on restricted data sets or invalid statistical analyses (which assume that every species provides independent information). Here we apply information‐theoretic statistical methods that are phylogenetically informed to a large data set on diving variables for birds and mammals to describe the allometry of diving. Body mass is strongly related to all dive variables except dive:pause ratio. We demonstrate that many diving variables covary strongly with body mass and that they have allometric exponents close to 0.33. Thus, our results fail to falsify the oxygen store/usage hypothesis. The allometric relationships for most diving variables are statistically indistinguishable for birds and mammals, but birds tend to dive deeper than mammals of equivalent mass. The allometric relationships for all diving variables except mean dive duration are also statistically indistinguishable for all major taxonomic groups of divers within birds and mammals, with the exception of the procellariiforms, which, strictly speaking, are not true divers.

The respiratory and cardiovascular changes associated with the emersion response ofCarcinus maenas (L.) during environmental hypoxia, at three different temperatures

Summary1.When exposed to progressive hypoxia in shallow seawater,Carcinus maenas partially emerged into air and aerated its branchial chambers by reversing the direction of their irrigation. Emersion took place at a meanPI, O2 of 18 mm Hg at 6 °C, 21 mm Hg at 12 °C and 59 mm Hg at 17 °C.2.At low oxygen tensions submerged crabs underwent a progressive bradycardia. Heart rate first became significantly lower than the rate in normoxia below aPI O2 of 30 mm Hg at 6 °C, 40 mm Hg at 12 °C and below 60 mm Hg at 17 °C. The proportion of total time spent irrigating the gills in a reversed direction increased in hypoxic seawater (PI, O2< 50 mm Hg), but respiratory rate was unchanged.3.Emersion into air always occurred during a reversal of irrigation and was accompanied by prolonged reversals, with consequent aeration of the branchial chambers, and by an immediate and maintained tachycardia back towards the rate in normoxic seawater. Crabs emerging into a hypoxic atmosphere (

Mechanics of breathing during strenuous exercise in Thoroughbred horses

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Estimation of daily energy expenditure from heart rate and doubly labeled water in exercising geese

< 10mm Hg) showed neither a maintained reversal of irrigation nor a maintained tachycardia.4.The oxygen tension of the postbranchial blood (Pa,O2) was 94 mm Hg in crabs submerged in normoxic seawater (PI,O2 146 mm Hg) at 12 ° C. During progressive hypoxiaPa, O2 fell in direct proportion to the drop inPI,O2. Emersion caused no significant increase inPa, O2.5.The mean oxygen content of postbranchial blood (Ca, O2) was 0.96 vol. % at aPI,O2 of 145 mm Hg.Ca, O2 fell to 0.19 vol.-% in submerged crabs at a meanPI,O2 of 25 mm Hg but rose to 0.45 vol.-% following 10 min emersion into air at a meanPI, O2 of 22 mm Hg.6.The results provide evidence of a respiratory role for the emersion response and also of an adaptive role for the high affinity of the blood pigment inCarcinus.

Implantable data logging system for heart rate and body temperature: its application to the estimation of field metabolic rates in Antarctic predators

Summary1.Oxygen consumption

Heart Rate and Oxygen Consumption of Exercising Gentoo Penguins

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