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Feast or famine: Evidence for mixed capital-income breeding strategies in Weddell seals

Wheatley, K., Bradshaw, Corey J. A., Harcourt, R. and Hindell, Mark A. (2008). Feast or famine: Evidence for mixed capital-income breeding strategies in Weddell seals. Oecologia,155(1):11-20.

Document type: Journal Article
Citation counts: Scopus Citation Count Cited 27 times in Scopus Article | Citations

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IRMA ID A00003xPUB52
Title Feast or famine: Evidence for mixed capital-income breeding strategies in Weddell seals
Author Wheatley, K.
Bradshaw, Corey J. A.
Harcourt, R.
Hindell, Mark A.
Journal Name Oecologia
Publication Date 2008
Volume Number 155
Issue Number 1
ISSN 0029-8549   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-38649100036
Start Page 11
End Page 20
Total Pages 10
Place of Publication Germany
Publisher Springer
Field of Research 0501 - Ecological Applications
0608 - Zoology
HERDC Category C1 - Journal Article (DEST)
Abstract Evolved patterns of resource expenditure for reproduction have resulted in a life history continuum across species. A strictly capital-breeding strategy relies extensively on stored energy for reproduction, whereas income breeding uses energy acquired throughout the reproductive period. However, facultative income breeding has been shown in some classically capital-breeding animals, and was originally thought to provide a nutritional refuge for smaller females incapable of securing sufficient reserves during pre-partum foraging. We examined milk composition and milk output for the Weddell seal to determine to what degree lactation was aided by food intake, and what factors contributed to its manifestation. Milk composition was independent of maternal post-partum mass and condition, but did change over lactation. Changes were most likely in response to energetic and nutritional demands of the pup at different stages of development. During early lactation, females fasted and devoted 54.9% of total energy loss to milk production. Later in lactation 30.5% more energy was devoted to milk production and evidence suggested that larger females fed more during lactation than smaller females. It appears that Weddell seals may exhibit a flexible strategy to adjust reproductive investment to local resource levels by taking advantage of periods when prey are occasionally abundant, although it is restricted to larger females possessing the physiological capacity to dive for longer and exploit different resources during lactation. This supports the assumption that although body mass and phylogenetic history explain most of the variation in lactation patterns (20–69%), the remaining variation has likely resulted from physiological adaptations to local environmental conditions. Our study confirms that Weddell seals use a mixed capital–income breeding strategy, and that considerable intraspecific variation exists. Questions remain as to the amount of energy gain derived from the income strategy, and the consequences for pup condition and survival.
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Created: Tue, 05 May 2009, 14:12:46 CST by Sarena Wegener