Data and R code from 'Warming up to a new coat: moulting king penguins exhibit hyperthermia and increased peripheral heat loss'

Penguins undergo catastrophic moult, which causes increases in metabolic rate,7 insulation, and heat loss via thermal windows. Here, we investigated the timing of these8 physiological changes to test two hypotheses. Under the thermal challenge hypothesis, we9 expected an initial rise in heat dissipation effort (i.e., increased peripheral vasomotion) followed10 by a rise in core temperature, indicating a failed aAempt to prevent hyperthermia. Under the11 warm-up hypothesis, we expected an initial rise of core temperature concomitant or followed by12 an increase of peripheral vasomotion, indicating regulated hyperthermia, possibly to accelerate13 feather development. We tested these hypotheses using simultaneous measurements of core14 and surface temperatures in capive king penguins (<i>Aptenodytes patagonicus</i>). Core and surface15 temperatures increased drastically but concomitantly during moult, providing tentative support16 for the warm-up hypothesis. Moulting penguins were never seen panting, suggesting that17 increasing peripheral heat loss was sufficient to regulate moulting-induced hyperthermia. Core18 and subcutaneous temperatures in wild individuals resembled patterns measured in captivity,19 despite lower heat load and additional options for behavioural thermoregulation. Together, these20 results indicate that hyperthermia is prevalent during moulting in king penguins, which raises21 questions regarding the ability of wild penguins to properly thermoregulate during moult under22 a warming climate.