As the only creatures on earth to breed in the Antarctic winter, their survival, as well as those of their chicks, is put in jeopardy when the temperature falls to 40 below. So, instinctively, emperor penguins all converge on the same central point and begin to form a huddle. As those on the outside take the brunt of the cold, those on the inside take tiny steps that move the huddle in waves. The pack continues to shift and rotate from the center, so no one is left permanently in the cold. The formation often breaks down when those on the inside overheat, at which point the coldest penguins, which were on the outside, form a new center as the other members of the colony huddle around them.