9321745 Kunz In nature, the energy an adult devotes to reproduction will affect not only the survival of a particular litter, but its ability to produce future offspring. Pregnancy and lactation place especially high energy and nutrient demands on the female, which may increase her susceptibility to starvation or disease. Thus, energy devoted to pregnancy and lactation must be counterbalanced against the female's future reproductive potential. Compromise must also be reached in balancing length of gestation against duration of lactation. Gestation is relatively inexpensive compared to lactation, as nutrients can be transferred directly to the developing young and thermoregulatory costs are minimal. However, transport of the growing fetus can impede normal daily activities and increase risk of predation. Patterns of energy expenditure during pregnancy and lactation should thus reflect the costs of maintaining and transporting a fetus versus feeding and caring for developing young.%%% The goal of the proposed research is to conduct a series of field and laboratory experiments to measure the cost associated with pregnancy in an omnivorous tropical bat, Phyllostomus hastatus. Daily energy expenditure and allocation will be quantified by measuring field metabolic rate (using doubly-labeled water) and body composition (through isotope dilution) of females at progressive stages of pregnancy. Nocturnal time-budgets of foraging females will be constructed using radio-telemetry to test the hypothesis that foraging time is a trade-off between supplying the growing needs of the fetus and minimizing the cost of transporting a developing embryo. Diet composition and nutritional content will be analyzed to determine how diet composition correlates with the cost imposed by pregnancy. Completion of these projects will be integrated with comparable data in the same species to provide important insights into the costs and compromises associated with reproduc tion in an omnivorous volant mammal.***
