Weaning mass affects changes in body composition and food intake in harbour seal pups during the first month of independence
Date
2003-05
Authors
Muelbert, MMC
Bowen, WD
Iverson, Sara J.
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Abstract
In phocid seals, the transition to nutritional independence is abrupt, with females abandoning
their offspring after weaning and returning to sea. We hypothesized that body size at weaning may
play an important role in the nature of this transition. We studied the changes in body composition
and water flux of newly weaning harbour seals over the first 4-6 wk postweaning. Thirty-three pups
were dosed with deuterium oxide to estimate total body water (TBW) and a subset of 24 was dosed
twice to estimate changes in body composition and water flux. All pups lost body mass over the study
period, but TBW increased during the period of mass loss, indicating continued lean tissue growth.
Combined data from this and our early study indicated that heavy (>median mass) pups were
relatively fatter (41.0% vs. 37.1%) and had significantly greater total body energy at weaning than
did light (less than or equal tomedian mass) pups. Percentage TBW declined linearly over time in
light pups but was constant in heavy pups for the first 19 d postweaning and then declined linearly.
Both the temporal pattern and composition of mass loss differed between light and heavy pups.
Estimated food intake increased in the second 2 wk of study compared to the first 2 wk, in both
light and heavy pups, reflecting increased foraging success but at levels still insufficient to meet
daily expenditures of most individuals.
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Citation
Muelbert, MMC, WD Bowen, and SJ Iverson. 2003. "Weaning mass affects changes in body composition and food intake in harbour seal pups during the first month of independence." Physiological and Biochemical Zoology 76(3): 418-427. Copyright © 2003 The University of Chicago Press.