The Occurrence and Purpose of Huddling by Emperor Penguins During Foraging Trips

Abstract

Between May and October 1993, temperature/light recorders mounted on the backs of Emperor Penguins Aptenodytes forsteri on foraging trips recorded occasions when light intensities were consistent with night-time but temperatures exceeded 23°C (the upper limit of the sensors); ambient air temperatures were < −15°C. The most likely explanation for the low light and high temperatures is that the penguins huddled together to share body warmth. The penguins apparently huddled at night during journeys to and from the ice-edge, especially on arrival at the ice-edge, and occasionally between foraging days at sea. Between June and October, as day length and ambient temperatures increased, the frequency and duration of huddling events decreased. Away-from-colony huddling would reduce a penguin’s metabolic costs while resting on the sea-ice during cold periods and could reinforce a behaviour that is required to survive extended periods of fasting at the colony.