Once a year, penguins undergo a catastrophic moult replacing their en=re plumage during a fas=ng period on land or on sea-ice during which =me individuals can lose 45% of their body mass. In penguins, new feather synthesis precedes the loss of old feathers leading to an accumula=on of two feathers layers (double coat) before the old plumage is shed. We hypothesize that the combina=on of the high metabolism required for new feathers synthesis and the poten=ally high thermal insula=on linked to the double coat could lead to a thermal challenge requiring addi=onal peripheral circula=on to thermal windows to dissipate extraheat. To test this hypothesis, we measured the surface temperature of different body regions of cap=ve Gentoo penguins (Pygoscelis papua) throughout the moult under constant environmental condi=ons. The surface temperature of the main body trunk decreased during the ini=al stages of the moult, therefore sugges=ng a higher thermal insula=on. On the opposite, the periorbital region, a poten=al proxy of core temperature in birds, increased during these same early moul=ng stages. The surface temperature of bill, flipper and foot (thermal windows) tended to ini=ally increase during the moult period, highligh=ng the likely need for extra heat dissipa=on in moul=ng penguins. These results raise ques=ons regarding the thermoregulatory capaci=es of wild penguins during the challenging period of moul=ng on land in the current context of global warming.