Males of king penguins (Aptenodytes patagonicus) naturally fast during one month at the beginning of their breeding cycle in the sub‐Antarctic islands. Previous qualitative data have shown that this species adapts to prolonged fasting by mobilizing fat stores and minimizing protein loss and that this strategy ends with a progressive increase in protein utilization. In the present study, the quantification of nutrient utilization from body composition of captive birds indicates that, during the phase of protein conservation, 93% of the energy produced derives from the oxidation of fat stores, body protein accounting for the remainder (7%). Tissue composition analysis shows that integument (feathers, skin and subdermal fat) is the main lipid source (65% of the fat loss) during this period, and that pectoral muscles provide the majority of body protein (57% of the total loss). If the fast is prolonged until a body mass below 10 kg is reached, there is a progressive four‐fold increase (from 1 68 to 6.50 gN/24h) in nitrogen excretion, together with a progressive exhaustion of fat stores. This shift in fuel metabolism is not a direct consequence of total lipid depletion, because 22% of the initial fat content still remains when proteins are no longer spared. During this later metabolic phase, protein is not only provided by pectoral muscles (71% of the loss), but also by hindlimb muscles (13%), and there remains only 2% of the initial amount of lipid in the integument at the end of the fast. Total energy expenditure is close to the fasting basal metabolic rate during the phase of protein conservation (2.52 W/kg), but it increases by 33% (3.36 W/kg) during the phase of protein wasting. This difference is probably due to a rise in locomotor activity, that is interpreted as reflecting a stimulation of food foraging behaviour before the lethal depletion of nutrient reserves.
Trends in sea-bird population sizes reflect changes in marine resources, but are only vislble after years. Sea-blrds fast when breeding ashore and, therefore, breeding success largely depends upon body fuels accumulated at sea and food stored in the stomach for chicks. Using an automatic setup for identification and weighing of breeding king penguins Aptenodytespatagonicus, we demonstrate seasonal differences in the daily gain in body mass and duration of foraging trips of breeders at sea. Taking into account already available information, our data indicate that it takes longer for the breeders to obtain food when marine resources are decreas~ng. The overall gain in body mass of the birds at sea is unchanged. However, they accumulate larger body fuel reserves, which therefore increases their energetic safety margin at predictable times of lower food availability but reduces food brought back to the chicks. In contrast to these seasonal changes, variations in the duration of sojourns into the colony, when penguins come independently to feed the chicks, can be attributed to the stages of the breeding cycle. Our setup also enables discriminating when the breed~ng failure is either due to poor food provisioning at sea or to the inability of the birds to minimize the depletion of their energy reserves when ashore. Thus, it is now possible to use breeding penguins as continuous indicators of changes in marine resources, on a time-scale of only days or weeks, while at the same time avoiding human disturbance by entering colonies and handling the birds.
Birds and mammals have evolved many thermal adaptations that are relevant to the bioinspired design of temperature control systems and energy management in buildings. Similar to many buildings, endothermic animals generate internal metabolic heat, are well insulated, regulate their temperature within set limits, modify microclimate and adjust thermal exchange with their environment. We review the major components of animal thermoregulation in endothermic birds and mammals that are pertinent to building engineering, in a world where climate is changing and reduction in energy use is needed. In animals, adjustment of insulation together with physiological and behavioural responses to changing environmental conditions fine-tune spatial and temporal regulation of body temperature, while also minimizing energy expenditure. These biological adaptations are characteristically flexible, allowing animals to alter their body temperatures to hourly, daily, or annual demands for energy. They exemplify how buildings could become more thermally reactive to meteorological fluctuations, capitalising on dynamic thermal materials and system properties. Based on this synthesis, we suggest that heat transfer modelling could be used to simulate these flexible biomimetic features and assess their success in reducing energy costs while maintaining thermal comfort for given building types.
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