A central principle in life-history theory is that reproductive effort negatively affects survival. Costs of reproduction are thought to be physiologically based, but the underlying mechanisms remain poorly understood. Using female North American red squirrels (Tamiasciurus hudsonicus), we test the hypothesis that energetic investment in reproduction overwhelms investment in antioxidant protection, leading to oxidative damage. In support of this hypothesis we found that the highest levels of plasma protein oxidative damage in squirrels occurred during the energetically demanding period of lactation. Moreover, plasma protein oxidative damage was also elevated in squirrels that expended the most energy and had the lowest antioxidant protection. Finally, we found that squirrels that were food-supplemented during lactation and winter had increased antioxidant protection and reduced plasma protein oxidative damage providing the first experimental evidence in the wild that access to abundant resources can reduce this physiological cost.
Bibliographical noteWe thank all field technicians, especially Ainsley Sykes and Elizabeth Anderson, for field data collection and management. We are grateful to Paula Redman and Peter Thomson for technical assistance in isotope analyses for the doubly-labeled water work. Thanks to Patrick Bergeron for providing the chipmunk daily energy expenditure data. Thanks also to Neil Metcalfe, Bruce Lyon, and two anonymous reviewers for helpful comments on the manuscript. Research support was provided by Natural Sciences and Engineering Research Council (NSERC) of Canada (A. G. McAdam, S. Boutin, M.M. Humphries), the National Science Foundation (DEB-0515849, A. G. McAdam), Aboriginal Affairs and Northern Development Canada Northern Scientific Training Program (Q. E. Fletcher, S. B. Woods), the British Ecological Society (C. Selman), and the National Institute on Aging (AG17994 and AG21042; C. Leeuwenburgh) grants. Personal support was provided to Q. E. Fletcher and S. B. Woods by NSERC Postgraduate Scholarships, and to A. Y. Seo by the American Heart Association (0615256B). This is paper number 66 of the Kluane Red Squirrel Project.
- Antioxidant protection
- Daily energy expenditure
- Doubly-labeled water
- Life-history theory
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Fletcher, Q. E. (Creator), Selman, C. (Creator), Boutin, S. (Creator), McAdam, A. G. (Creator), Woods, S. B. (Creator), Seo, A. Y. (Creator), Leeuwenburgh, C. (Creator), Speakman, J. (Creator) & Humphries, M. M. (Creator), Dryad Digital Repository, 8 Nov 2012