Pascale speculated that both geese and penguins control blood flow to their feet in order to keep them warm. If you measured the temperature of a penguin’s right foot, you would see that the temperature cycles. It would be cold and then warm, cold and then warm, and so on. While one foot is cold, the other foot is warm. If you graphed the temperature of both feet, you would see the cycling of temperature as the feet take turns being warmed then cooled.