Cynthia Hornung, M.S., 2001
(Raptor Rehabilitation Center, Alabama)Department of Biology
Murray State University, Murray, KY 42071
Maintenance of energy balance in small mammals: the importance of nutrient absorption rate and gut size.Abstract:
The roles of changes in gut capacity that have been documented in the laboratory remain unclear in the context of animals in the wild. My objective, therefore, was to further investigate the bio-energetic mechanisms that aid smaill free-living mammals in maintainting energy balance. I measured the vital organs, fiber and protein content of the diet, gut organs and the rate of glucose upatake within the small intestine of a male free-living white-footed mice among seasons and of lactating female white-footed mice during the summer. In males the kidney was larger in the summer than in the winter, which corresponded to a greater intake of protein. The caecum was longer in winter compared to fall and the caecum and colon were found to be heavier in spring compared to summer. The differences in caecum and colon size paralleled differences in the fiber content of the diet among the seasons. No difference was found in diet composition between the sexes. All gut organs were larger and the rate of glucose uptake was greater in lactating females as compared to summer caught males. Through the seasons, an omnivorous diet and the ability to enter daily torpor may have allowed this species to escape from negative consequences associated with changes in energy demand. An increase in gut tissue and rate of nutrient uptake are apparently only implemented in this species during periods of extreme energy demand (i.e., lactation).
Constructed by Brandon Kellie on 6/26/01.
