Ecological energetics of Eudyptes penguins at Marion Island

Abstract

Macaroni Penguins (Eudyptes chrysolophus) and Rockhopper Penguins (E. chrysocome) breed sympatrically at Marion Island in the sub-Antarctic, where they account for a substantial proportion of the avian biomass breeding at the island. This thesis documents the energy requirements of the two species during their respective breeding and moulting cycles at the island. Resting metabolic rates, calculated from lowest, stable rates of oxygen consumption over 24 h, averaged 25 % greater than basal metabolic rates predicted from allometric equations. Body temperatures of the penguins and the relationships between metabolic rates and temperature were investigated over a range of -10°C to 25°C. Lower critical temperature of Rockhopper Penguins was between 0°C and 5°C, but that of Macaroni Penguins could not be clearly ascertained. Measured metabolic rates of other species of penguins are reviewed and intra- and inter-specific differences in metabolic rates are discussed. In contrast to most penguins measured, individuals maintained in zoos or held in captivity for long periods had metabolic rates lower than predicted basal levels.