Acid-Base Balance in Three Species of Antarctic Penguins Exposed to Thermal Stress

Abstract

Antarctic penguins occasionally encounter intense solar radiation while in the rookery. Heat dissipation can become a problem for brooding adults, and panting is necessary sometimes for long periods of time. This study has quantitatively examined changes in blood gases and acid-base balance in three species of penguins as a result of thermal loads. The species were Adelie penguins (Pygoscelis adeliae), chinstrap penguins (P. antarctica), and gentoo penguins (P. papua). During moderate heat loads body temperature increased and panting began but arterial and venous pH, $P_{CO_{2}}$, and $P_{O_{2}}$ remained within the normal range. Under high heat stress the panting rate reached a maximum and severe respiratory alkalosis resulted. The gentoo penguins were observed to better tolerate thermal challenges than the other two species. Differences between the in vitro and in vivo blood buffer slopes were also noted between the species.