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Motivated by conservation concerns, we assessed whether Sigmodon hispidus (hispid cotton rat) affects the realized niche of Peromyscus polionotus ammobates (Alabama beach mouse). After experimentally removing S. hispidus and accounting for spatial autocorrelation in our data, we found weak evidence for an increase in habitat use by P. p. ammobates at locations previously occupied by S. hispidus. This pattern is consistent with a niche-constriction hypothesis, and was not observed on 2 control grids where removals were not conducted. Our results suggest that removal of S. hispidus from habitat remnants immediately following catastrophic hurricanes ameliorates extinction risk of P. p. ammobates, but we also stress the inferential limitations of our data and the need for further investigation of competitive interactions between these species.

Little is known about abundance-climate relationships for animals because few long-term field studies address the issue. We present results from a 20-year study of abundance of Peromyscus leucopus (white-footed mouse) and Microtus pennsylvanicus (meadow vole). P. leucopus exhibited a biennial cycle with an overall population increase. M. pennsylvanicus did not exhibit a population cycle, and population size declined. We attribute long-term changes in abundance of both species to succession from grass-dominated to tree-dominated vegetation. The only significant association we found between abundance of either species over 20 years and 4 climate variables was a positive relationship between M. pennsylvanicus and summer precipitation. However, all but 1 of the potential abundance-climate relationships were significant when temporal subsets of the original data were analyzed. Weak associations may exist between climate and abundance that are contingent upon other unidentified factors, which further suggests that abundance-climate correlations are sensitive to the particular time frame of a study.