Resting Metabolic Rates and Respiratory Quotients of Gray Seals (Halichoerus grypus) in Relation to Time of Day and Duration of Food Deprivation

Resting metabolic rates (RMR) and respiratory quotients (RQ) were measured in seven gray seals, Halichoerus grypus (three adults and four juveniles), at different times of day. Resting metabolic rates did not change significantly throughout the day. The lack of detectable diel changes in RMR may be attributed to the large body mass of the animals or to limitations of the experimental design. Respiratory quotient values differed significantly with time of day, being higher in the morning compared with other time periods. Further analysis indicated that apparent changes in RQ could be attributed to the confounding effect related to duration of food deprivation. Once corrected for this effect, RQ did not change in relation to time of day. The latter result suggests that gray seals may enter a starvation state after 24 h of food deprivation.