Animals that employ 'capital breeding' rely principally on stored reserves to support reproduction. Many species of Phocid seals appear to rely on a combination of stored reserves and ongoing foraging to support lactation costs. The Weddell seal (Leptonychotes weddellii) of Antarctica had been thought to fast during its relatively long lactation (6-8 weeks), but evidence from feeding biomarkers, diving behavior and maternal mass loss suggests that most females feed, at least in late lactation. Feeding is predicted to be especially important in smaller females with limited body stores of substrates and energy. The proposed research will investigate capital expenditure, lactation energetics and the importance of food intake in the Weddell seal using a novel multimarker approach to determine: (1) Changes in maternal capital stores over the course of lactation; (2) Maternal energy expenditure; (3) Maternal milk production including transfer of energy, fat, water and protein to pups; (4) Timing of the onset of feeding in lactating females and pups; (5) Contribution of food intake to the maternal energy and substrate budget; and (6) Duration of the lactation period and nature of the weaning process. By labeling maternal and offspring body water pools with two distinct isotopes of hydrogen, we can measure water turnover, changes in body composition, and milk transfer to pups, even if pups begin to forage. Onset of feeding by mothers and pups will be assessed from circulating levels of dietary biomarkers and will be compared to diving activity obtained from time depth-recorders and radiotransmitters. The quantitative importance of food energy intake to lactating seals will be determined by a comparison of summed energy expenditures to energy mobilization form stores in animals known to be fasting or feeding. Detailed estimates of energy and protein budgets of mother-pup pairs will be developed. Prey samples will be analyzed for analysis of gross composition, biomarker and energy content, and key hormones and metabolites in lactating Weddell seals will be monitored. From these data, the relative importance of capital expenditure and food intake, and of energy vs. protein, in the evolution of a mixed capital and income breeding strategy will be evaluated. To achieve broader impact for this work, a dynamic, multi-level outreach package, typical of the Smithsonian National Zoological Park's award-winning science outreach program, will be developed. This package will include exhibits located at the National Zoo that involve a range of techniques such as computer-based multi-media and video presentations, interactive exhibits, demonstrations and one-on-one interpretive interactions between scientists and zoo visitors. A web page about the project will be added to the National Zoo's extraordinarily popular web site. Scientists involved in the project will meet quarterly with youths from the Columbia Science Workshop, an NSF-funded science program for under-served minority youths located in the Zoo's neighboring community and run by the Zoo's science outreach staff.
