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COMPARATIVE NITROGEN REQUIREMENTS OF SMALL MAMMALS FOR REPRODUCTION: CONSEQUENCES OF DIETARY NICHE OR LIFE-HISTORY STRATEGY?
Citation:
Parsons, J. L., D. Leslie, E. C. Hellgren, R. L. Lochmiller, AND E E. Jorgensen*. COMPARATIVE NITROGEN REQUIREMENTS OF SMALL MAMMALS FOR REPRODUCTION: CONSEQUENCES OF DIETARY NICHE OR LIFE-HISTORY STRATEGY? Presented at Annual Mtg. Southwestern Association of Naturalists, Hays, KS, 04/01-30/2001.
Description:
Nitrogen dynamics in animal communities are of increasing interest, given growing amounts of environmental nitrogen and the key nutritional role of this element. We performed feeding trials on the hispid cotton rat (Sigmodon hispidus) and the fulvous harvest mouse (Reithrodontomys fulvescens) to determine nitrogen requirements for reproduction. Because of the relatively low-protein diet of wild cotton rats, we predicted that S. hispidus would have a lower nitrogen requirement. Females were fed one of seven experimental diets (1-3.5% nitrogen) from the third trimester of gestation through lactation. Offspring were weighed regularly from birth until weaning, and growth rate was regressed on maternal nitrogen intake. Breakpoint analysis indicated that S. hispidus required 2.31% dietary nitrogen (2.50 g/kg0.75) and R. fulvescens required 1.29% nitrogen (2.04 g/kg0.75) for maximal reproduction. Although our prediction based on dietary habits was not upheld, our data indicate contrasting physiological responses to changing nutritional conditions, perhaps dictated by a life-history dichotomy between these two species. Repercussions of increasing environmental nitrogen on population dynamics and species composition will be discussed. The views expressed are those of the authors and do not necessarily reflect the views and policies of the U.S. Environmental Protection Agency (EPA).