King penguin chicks lower their body temperature to conserve energy, reports a study in Nature Communications this week. This process, known as heterothermy, is a surprising find in such a large bird, but may explain how the chick is able to fast for up to five months in winter while waiting for the parents’ return.Gotz Eichhorn and colleagues measured the body temperature of free-ranging king penguin chicks and found that the chicks dropped their body temperature in response to factors such as cold meals and adverse weather. This process enables them to conserve energy during their long period of growth in a harsh climate while also having to intermittently fast over many months.