Recovery from Swimming‐Induced Hypothermia in King Penguins: Effects of Nutritional Condition

Abstract

We investigated changes in the rate of oxygen consumption (V O2) and body temperature of wild king penguins (Aptenodytes patagonicus) in different nutritional conditions during recovery after exposure to cold water. Over time, birds undertook an identical experiment three times, each characterized by different nutritional conditions: (1) having recently completed a foraging trip, (2) after fasting for many days, and (3) having been refed one meal after the fast. The experiments consisted of a 2-h session in a water channel followed by a period of recovery in a respirometer chamber on land. Refed birds recovered significantly more quickly than fed birds, in terms of both time to reach resting V O2 on land and time to reach recovery of lower abdominal temperature. Previous work found that when penguins are in cold water, abdominal temperatures decrease less in refed birds than in fed or fasted birds, suggesting that refed birds may be vasoconstricting the periphery while perfusing the gut region to access nutrients. This, alongside an increased resting [V O2], seems the most reasonable explanation for why refed birds recovered more quickly subsequent to cold-water exposure in this study; that is, vasoconstriction of the insulative periphery meant that they lost less heat generated by the body core.

Long-term fasting decreases mitochondrial avian UCP-mediated oxygen consumption in hypometabolic king penguins

“…A potential role of avUCP in these diving-related processes is also reinforced by the marked upregulation of avUCP expression after acclimation to sea-water in king penguin juveniles (59). Conversely, under adequate conditions of stimulation, activation of mitochondrial proton leaking may contribute to rewarming after diving sessions in a situation of low muscle contractions (33). Studies are clearly required to test these speculative hypotheses, although it is already apparent that exploring the mitochondrial mechanisms that control energy dissipating processes are of particular interest in understanding metabolic adaptations of living under conditions of harsh energetic constraints.…”

Thermal strategies of king penguins during prolonged fasting in water

“…Furthermore, as the VȮ 2 -heart rate relationship used to estimate VȮ 2 from the recording of heart rate in free-ranging king penguins (Froget et al, 2004) was derived from treadmill exercise in air (Fahlman et al, 2004), it might also be possible that the VȮ 2 estimate for the first hour after foraging is underestimating the true costs. Halsey et al (2008) determined the costs associated with recovery from hypothermia in king penguins after they had been swimming inside a shallow water channel for 2 h. During these trials in water, the abdominal temperature of fasted birds (M b 10.6 kg) declined by 1-6°C (maximum; depending on thermistor position within the abdomen). When recovering in air, the sVȮ 2 of fasted birds reached values ∼32 ml min −1 kg −1 (Halsey et al, 2008;their fig.…”

“…Halsey et al (2008) determined the costs associated with recovery from hypothermia in king penguins after they had been swimming inside a shallow water channel for 2 h. During these trials in water, the abdominal temperature of fasted birds (M b 10.6 kg) declined by 1-6°C (maximum; depending on thermistor position within the abdomen). When recovering in air, the sVȮ 2 of fasted birds reached values ∼32 ml min −1 kg −1 (Halsey et al, 2008;their fig. 1A).…”