Effect of fasting on the V̇o2-fhrelationship in king penguins,Aptenodytes patagonicus

Abstract

King penguins ( Aptenodytes patagonicus) may fast for up to 30 days during their breeding period. As such extended fasting may affect the relationship between the rate of O₂consumption (V̇o₂) and heart rate ( f_H), five male king penguins were exercised at various speeds on repeated occasions during a fasting period of 24–31 days. In addition, V̇o₂and f_Hwere measured in the same animals during rest in cold air and water (4°C). V̇o₂and f_Hat rest and V̇o₂during exercise decreased with fasting. There was a significant relation between V̇o₂and f_H( r²= 0.56) that was improved by including speed, body mass ( M_b), number of days fasting ( t), and a cross term between f_Hand t ( r²= 0.92). It was concluded that there was a significant change in the V̇o₂- f_Hrelationship with fasting during exercise. As t is measurable in the field and was shown to be significant and, therefore, a practical covariate, a regression equation for use when birds are ashore was obtained by removing speed and M_b. When this equation was used, predicted V̇o₂was in good agreement with the observed data, with an overall error of 3.0%. There was no change in the V̇o₂- f_Hrelationship in penguins at rest in water.