Yvon Le Maho

Centre d'Ecologie et Physiologie Energetiques, 23, rue Becquerel, 67087 Strasbourg Cedex 2, France, e-mail yvon.lemaho@c-strasbourg.fr

Le Maho, Y. 1999. How Emperor Penguins and King Penguins face physiological limitations to breed and forage under natural conditions.In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban: 1468. Johannesburg: BirdLife South Africa.

While breeding and moulting, Emperor Aptenodytes forsteriand King Penguins A. patagonicus alternate extended fasts on sea-ice or on land with foraging trips far out at sea where they make long, deep dives. Male Emperor Penguins, in contrast to Kings, assume the entire two month incubation task during the extreme cold of the Antarctic winter. While mating and incubating, male Emperors fast for 3-4 months at air temperatures usually below -20º C in winds often blowing at 100 km/h. We used deuterium-labelled water to determine energy and water turnover in incubating male Emperor Penguins. Huddling behaviour during incubation is crucial; it allows significant energy conservation, as indicated by their mean metabolic rate (MR) 25% below their resting MR, measured at thermoneutrality in controlled conditions. Emperor males have very low water turnover rates and are consequently able to go without drinking or eating snow for extended periods. Deep diving in both species presents a demanding physiological and ecological challenge. We used implanted data loggers, to study how King Penguins manage dives lasting up to 8 minutes and reaching depths of 300 m or more. We found that they allow their lower abdominal temperature to drop as low as 11º C. This controlled hypothermia, and ensuing reduced MR, would save energy, significantly contributing to their ability to make deep dives.