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POPULATION DYNAMICS OF HISPID COTTON RATS (SIGMODON HISPIDUS) ACROSS A NITROGEN AMENDED LANDSCAPE
Citation:
Clark, J. E., E. C. Hellgren, E E. Jorgensen*, S. J. Tunnell, D. M. Engle, AND D. Leslie. POPULATION DYNAMICS OF HISPID COTTON RATS (SIGMODON HISPIDUS) ACROSS A NITROGEN AMENDED LANDSCAPE. CANADIAN JOURNAL OF ZOOLOGY 81:994-1003, (2003).
Description:
Population dynamics of some small-mammal species appear to be regulated by plant-community structure, vegetative cover, plant diversity, and food quality. Thus, plant community changes associated with nitrogen additions would likely impact dynamics and structure of small-mammal populations. We conducted a mark-recapture experiment to examine how population dynamics of hispid cotton rats (Sigmodon hispidus) respond to low-level nitrogen additions in an old-field grassland. The experimental design consisted of 16, 0.16-ha plots with 4 replicates of each treatment combination (fenced, nitrogen addition; unfenced, nitrogen addition; fenced, control; unfenced, control). We predicted densities, reproductive success, movement probabilities, and survival of cotton rats would be higher on nitrogen-amended plots because of increased aboveground biomass and cover. Population densities of cotton rats tended to be highest on nitrogen-fenced plots, but densities on unfenced-nitrogen plots were similar to control and fenced plots. We observed no distinct patterns in survival, reproductive success, or movement probabilities with regards to nitrogen. However, survival and reproductive success tended to be higher for cotton rats on fenced plots compared with unfenced plots and was likely attributed to decreased predation on fenced plots. As low-level nitrogen additions continue to be applied and plant succession progresses, we predict cotton rat population parameters on control plots, especially fenced plots with no nitrogen addition, will eventually exceed those on nitrogen-amended plots as a result of higher plant species diversity, food availability, and better quality cover.