R. M. Bevan

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.

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

The metabolic rate of free-ranging animals is difficult to measure, but of great importance in understanding the interactions of a species with its environment. Heart rate can, if correctly validated and calibrated, give an estimate of metabolic rate, with both a fine time resolution and over long periods. The telemetry of heart rate is well documented, but is not appropriate over long ranges (possibly several thousands of kilometres) or for diving species. An implantable data logger has therefore been developed for the long term recording of heart rate and body temperature. The logger is built using hybrid and ASIC construction techniques, weighs 20 g and measures 55×24×6 mm. The device is programmable, and its solid-state memory holds over 70 days of data if, for example, heart rate is counted and stored every minute. Current consumption is 155 μA while logging, 50 μA during a programmable initial delay period, and less than 1 μA when the logger closes down after filling its memory. These loggers have been deployed for two field seasons in gentoo penguins, black-browed albatross and fur seals.

Heart Rate and Oxygen Consumption of Exercising Gentoo Penguins

Heart rate (fH) and oxygen consumption (V̇o2) were recorded from gentoo penguins walking on a variable-speed treadmill. After an initial increase, fH and V̇o2 increased linearly with walking speed. A curvilinear regression equation best described the relationship between fH and V̇o2. Over a 3-d period, fH and V̇o2 were recorded continuously from six gentoo penguins that had been injected with doubly labeled water (DLW). When fH was used to predict V̇o2 over the 3 d, the estimate uwas not significantly different from the measured V̇o2 with an error (−1.0%) that was less than that produced by the DLW method (+ 1.6%). The estimate produced by the fH technique was also accurate when applied both to shorter periods (30 min) and to periods of activity and inactivity. Seven gentoo penguins were also swum in a water channel, and fH and V̇o2 were again recorded. The relationship between fH and V̇o2 determined from the birds in the water channel was not significantly different from that obtained from the walking birds. It is seems reasonable that, since the fH − V̇o2 relationship of most behaviors of the penguin have been determined while the animal is walking and swimming, fH can be used to predict the metabolic rate of free-ranging animals.

Daily energy expenditure of tufted ducks: a comparison between indirect calorimetry, doubly labelled water and heart rate

1. The doubly labelled water (DLW) technique has been used to estimate the rate of energy expenditure of many species of free-living birds including some that dive. The technique, however, has never been validated in an actively diving bird. 2. DLW was used to estimate the metabolic rate of the diving tufted duck and the derived estimate was compared with the value obtained by direct respirometry. All the equations used to calculate the energy expenditure from DLW produced estimates for individual birds with large ranges of errors. Even the most accurate equation, S4 (Speakman 1993), underestimated oxygen consumption by an average of 15.6%. The range of errors for that equation (− 83 to + 67%) shows that in the diving tufted duck, the DLW technique has a reduced precision3. This reduced precision is probably due to the high water flux measured. As a high water turnover is likely to be a consistent feature of many diving and swimming birds and mammals, care should be exercised in interpreting measurements derived from DLW for these animals4. Heart rate, used as another indicator of metabolic rate, was also monitored in four of the birds. Although there was again a wide range of individual errors (− 38 to + 71%), the mean estimate was not significantly different from those derived from DLW and direct respirometry

Impact of Externally Attached Loggers on the Diving Behaviour of the King Penguin

The impact of relatively small externally attached time series recorders on some foraging parameters of seabirds was investigated during the austral summer of 1995 by monitoring the diving behaviour of 10 free‐ranging king penguins (Aptenodytes patagonicus) over one foraging trip. Time‐depth recorders were implanted in the abdominal cavities of the birds, and half of the animals also had dummy loggers attached on their backs. Although most of the diving behaviour was not significantly affected by the external loggers ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Pulmonary Blood Flow at Rest and during Swimming in the Green Turtle, Chelonia mydas

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Survival rates of adult Reed Warblers Acrocephalus scirpaceus at a northern and southern site in England

\end{document} ), the birds with externally attached loggers performed almost twice as many shallow dives, between 0 and 10 m depth, as the birds without external loggers. These shallow dives interrupted more frequently the deep‐diving sequences in the case of birds with external loggers (percentage of deep dives followed by deep dives: 46% for birds with implants only vs. 26% for birds with an external attachment). Finally, the distribution pattern of the postdive durations plotted against the hour of the day was more heterogeneous for the birds with an external package. In addition, these penguins had extended surfacing times between two deep dives compared to birds without external attachments ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape