Body condition at weaning affects the duration of the postweaning fast in gray seal pups (Halichoerus grypus)
Date
2008-05
Authors
Noren, Shawn R.
Boness, Daryl J.
Iverson, Sara J.
McMillan, Jim
Bowen, W. Don
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Abstract
Gray seals (Halichoerus grypus) undergo a terrestrial postweaning fast (PWF) that depletes
energy reserves acquired during the suckling interval. Plasticity in PWF duration may ensure that
pups of variable body condition depart for sea with adequate energy reserves. To test this
hypothesis, we examined body condition of 30 gray seal pups at weaning and monitored their PWF
duration. On average, fat accounted for 47.3% +/- 0.7% of their 53.2 +/- 1.3-kg weaning mass.
Although fasting duration averaged 21 +/- 1.1 d (n = 28), there was considerable variation in
fasting duration (9 to >31 d) and the resulting age when pups departed to sea (26 to >49 d).
Percent fat at weaning (38.6%-54.6%) was positively correlated with fasting duration (n = 28, r =
0.376, P = 0.0489). In contrast, total body gross energy (735.3-1,447.4 MJ) and body mass (39.0-66.0
kg) were not correlated with fasting duration. Thus, body composition, not overall body reserves,
predicted fasting duration, but the effect was weak, indicating that other factors also account for
the observed variation in fasting duration. We speculate that pups with greater percent fat more
effectively utilized lipid and conserved protein while meeting metabolic costs throughout the PWF.
As a result, fatter pups extended the PWF duration, which may be critical for development of diving
physiology and may have facilitated their survivorship to age 1.
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Citation
Noren, Shawn R., Daryl J. Boness, Sara J. Iverson, Jim McMillan, et al. 2008. "Body condition at weaning affects the duration of the postweaning fast in gray seal pups
(Halichoerus grypus)." Physiological and Biochemical Zoology 81(3): 269-277. Copyright © 2008 The University of Chicago Press.