To investigate thermoregulatory adjustments at sea, body temperatures (the pectoral muscle and the brood patch) and diving behavior were monitored during a foraging trip of several days at sea in six breeding king penguins Aptenodytes patagonicus. During inactive phases at sea (water temperature: 4-7 degrees C), all tissues measured were maintained at normothermic temperatures. The brood patch temperature was maintained at the same values as those measured when brooding on shore (38 degrees C). This high temperature difference causes a significant loss of heat. We hypothesize that high-energy expenditure associated with elevated peripheral temperature when resting at sea is the thermoregulatory cost that a postabsorptive penguin has to face for the restoration of its subcutaneous body fat. During diving, mean pectoral temperature was 37.6 +/- 1.6 degrees C. While being almost normothermic on average, the temperature of the pectoral muscle was still significantly lower than during inactivity in five out of the six birds and underwent temperature drops of up to 5.5 degrees C. Mean brood patch temperature was 29.6 +/- 2.5 degrees C during diving, and temperature decreases of up to 21.6 degrees C were recorded. Interestingly, we observed episodes of brood patch warming during the descent to depth, suggesting that, in some cases, king penguins may perform active thermolysis using the brood patch. It is hypothesized that functional pectoral temperature may be regulated through peripheral adjustments in blood perfusion. These two paradoxical features, i.e., lower temperature of deep tissues during activity and normothermic peripheral tissues while inactive, may highlight the key to the energetics of this diving endotherm while foraging at sea.
"In most eider colonies in Iceland, the nest density is closer to 20–250 nests/ha and there is more vegetation available for shelter than at Rif (2000 nests/ ha), so females do not pass other nests as often. Eiders are on a tight energy budget during incubation and it could be that sitting on an unguarded clutch when they have been disturbed from their own nest (i.e. by the eiderdown collectors) is a strategy to minimize heat loss from the brood patch on the bird (Schmidt et al. 2006). Eiders may egg dump, so incubation in other nests may reflect differential investment in care of their own offspring. "
[Show abstract][Hide abstract] ABSTRACT: Capsule Common Eiders at Rif in west Iceland commonly show joint nest attendance, which may be an exaggerated behavioural response to the visual stimulus of many nests so close to their own nest. This represents a new insight into incubation behaviour in colonies with extremely high nest densities.
Bird Study 01/2015; 62(1). DOI:10.1080/00063657.2014.993591 · 1.11 Impact Factor
"This was achieved by calculating the length of time from the end of the water channel session to the point at which lower abdominal temperature had increased to within 0.5ЊC of the lower abdominal temperature before the start of the water channel session. Half of 1ЊC was chosen because the variation in body temperatures of individual birds onshore is represented by a standard deviation that is less than this (Schmidt et al. 2006). "
[Show abstract][Hide abstract] 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.
"Secondly, glycolysis produces less ATP per mole of glucose than the Krebs cycle, and that it takes longer at the surface to remove lactate from the blood before diving again than after aerobic dives. Therefore, it is generally thought that diving seabirds use aerobic metabolism in most serial dives (Butler and Jones, 1997; Kooyman and Ponganis, 1998; Ponganis and Kooyman, 2000; Schmidt et al., 2006). Past research has shown that the body temperature of birds can drop during dives in cold water, which probably lowers metabolic rate (outside of exercising muscles) and thereby allows extension of aerobic dive duration (Culik et al., 1996; Bevan et al., 1997; Handrich et al., 1997; Butler, 2000). "
[Show abstract][Hide abstract] ABSTRACT: A major challenge for diving birds, reptiles, and mammals is regulating body temperature while conserving oxygen through a reduction in metabolic processes. To gain insight into how these needs are met, we measured dive depth and body temperatures at the core or periphery between the skin and abdominal muscles simultaneously in freely diving Brünnich's guillemots (Uria lomvia), an arctic seabird, using an implantable data logger (16-mm diameter, 50-mm length, 14-g mass, Little Leonardo Ltd., Tokyo). Guillemots exhibited increased body core temperatures, but decreased peripheral temperatures, during diving. Heat conservation within the body core appeared to result from the combined effect of peripheral vasoconstriction and a high wing beat frequency that generates heat. Conversely, the observed tissue hypothermia in the periphery should reduce metabolic processes as well as heat loss to the water. These physiological effects are likely one of the key physiological adaptations that makes guillemots to perform as an efficient predator in arctic waters.
Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology 07/2007; 147(2):438-44. DOI:10.1016/j.cbpa.2007.01.014 · 1.97 Impact Factor
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