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Primary Research Interests of the Laboratory:
Acquiring sufficient energy and essential nutrients to support maintenance, growth, and reproduction is critical to all organisms. Although many species meet their demand for essential nutrients while acquiring energy, this is not true for all species. Because the availability of essential nutrients can vary with season and habitat and the demand for these nutrients can vary between species and with age, season, and reproductive condition, different species have often evolved very different foraging strategies and physiological mechanisms that allow them to cope with nutritional constraints.
Our research focuses on understanding how nutritional constraints influence the reproductive performance, ecology, and the evolution of vertebrate life histories. Using a multidisciplinary approach, we rely on the principles of behavioral ecology to understand reproductive and foraging behaviors, physiological ecology to understand nutrient utilization and energy expenditure, and the methods of analytical and organic chemistry for nutritional analyses.
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Current Research Projects:
Calcium intake, mineral mobilization from bone, and reproductive performance in mammals.
The primary emphasis of the lab is understanding calcium constraints on reproductive performance. From conception to weaning, mammalian mothers supply most to all of the minerals necessary for offspring skeletal development. Calcium and other mineral supplied to pups comes from two sources, the maternal diet and mineral mobilized from maternal bone. Our work focuses understanding how calcium intake and bone mineral content interact and how these interactions ultimately influence offspring development. We believe that calcium availability can ultimately act as one of several factors which contribute to variation in litter size both within and between species. Auburn University undergraduates and high school students are involved in many aspect of this research.
Ongoing research on mice: Christina Booher is currently examining the effect of dietary calcium on reproductive performance in white footed mice. She is manipulating calcium content of mothers diets, using dual-x ray absorptiometry to examine changes in bone density, and examining reproductive performance by monitoring number of offspring and offspring growth. Dr Hood is examining constraints on mineral mobilization from bone during reproduction in laboratory mice and determining if locomotor stress acts to constrain the about of mineral that is mobilized during reproduction.
Ongoing research on seals: Seals produce milk that is higher in phosphorus than calcium but the significance of this deviation from the high calcium, low phosphorus ratio found in the milk of most mammals is unknown. Dr Hood collected samples from lactating Weddell seals in Antarctica in collaboration with Drs Oftedal and Eisert of the Smithsonian’s National Zoo. We are currently analyzing milk and tissue samples from these animals. This work is expected to improve our understanding of the relationship between milk composition and maternal and pup bone mineral dynamics.
Ongoing research on bats: Unlike other small mammals, bats give birth to only 1 or 2 young per reproductive bout. Many investigators have speculated that the small litter sizes of bats are in part associated with the low calcium content of their insectivorous diet. Both Hood and Booher have both examined mineral dynamics in insectivorous bats and continue to do in various side projects.
Milk composition methods development.
In collaboration with Dr. Olav Oftedal, Smithsonian Environmental Research Center and Dr. Mary Beth Voltura, SUNY Cortland, we have developed a technique for analyzing the proximate composition of milk collected from small mammals using a CHN elemental analyzer. A validation of this method will submitted for publication shortly. In addition, we wrote a book chapter for the ‘Ecological and Behavioral Methods for the Study of Bats’ (2nd ed., Kunz and Parsons, eds.) that makes recommendations for the collection and analysis of milk collected from small mammals. These procedures require considerable care over those used for sample collection and sample analysis for larger mammals. This book will be published in 2008.
Factors influencing milk composition.
With new methods available for measuring milk composition in individual animal, we have begun to examine factors contributing to individual variation in milk composition and production. In collaboration with Dr. Allyson Walsh at the Lubee Bat Conservancy, we are examining the effects of maternal condition and experience on milk composition and production in the island flying fox. These samples are currently being analyzed and we hope that the results of this work will be available in the near future.
Carotenoid absorption, breeding coloration, and body condition.
Ongoing research in birds: In collaboration with Geoff Hill at Auburn University, we are examining the combine effects of body condition, parasite load, and intake of dietary carotenoids on plumage coloration in American Goldfinch. Our first captive multifactorial test of the combine effects of these variables on breeding coloration will be submitted for publication in the near future. In addition, we are interested in determining if changes in gut morphology and dietary fat during molt influence carotenoid absorption.
Ongoing research in fish: Ed Parsons is examining why a carnivorous fish, the bluegill sunfish, consumes algae when it doesn’t appear to have the physiological and anatomical characteristics that would allow it to use algae as a source of energy. Because it has often been noted that nesting males display greater yellow-orange breast coloration than non-nesting males and females, we believed that this coloration could be derived from carotenoids, which are abundant in algae. Ed is currently examining the phenomenon for his MS at CCU.
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