Correlates of seasonal changes in metabolism in Atlantic harbour seals ( Phoca vitulina concolor)

• Published in: Canadian Journal of Zoology
• Main Authors: Rosen, D A, Renouf, D
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1998
• Subjects: Phoca vitulina
• Online Access: http://dx.doi.org/10.1139/z98-080; http://www.nrcresearchpress.com/doi/pdf/10.1139/z98-080

This study tested the hypothesis that seasonal variation in resting metabolic rate (RMR) was more closely related to changes in total energy use than to energy intake. It also quantified the extent to which variation in metabolism contributed to changes in total energy expenditure. RMR, gross energy intake, and body mass and composition were measured in six captive Atlantic harbour seals (Phoca vitulina concolor) over 16 months. Gross energy intake during the year (across all seals) averaged 25.4 ± 4.1 MJ/d (mean ± SD). The energy used by the seals E used a composite measure of energy expenditure from ingested energy and tissue catabolism) averaged 19.2 ± 3.4 MJ/d. RMR averaged 11.2 ± 1.5 MJ/d during the year, while mass-corrected metabolism declined with age. The seals displayed significant changes in both absolute and mass-corrected metabolism during the year. Overall, E used was a stronger predictor of changes in metabolism than either gross energy intake or body mass. Mass-corrected metabolic rate was more closely related to E used than was absolute metabolism. Energy changes in metabolism during the year (range = 6.9 ± 1.9 MJ/d) were minor compared with those in E used (27.8 ± 7.3 MJ/d). These results suggest that seasonal changes in metabolism were a response to, or facilitated by, concurrent changes in E used but were not the cause of variation in E used . Rather, variation in both RMR and E used was the result of changes in other bioenergetic components of the seals' energy budget, such as activity.