Responses of mice to fluctuating habitat quality II. A supplementation experiment
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We studied numerical and physiological responses of populations of pinyon mice (Peromyscus truei) during low abundance to supplemental feeding in 1990-1991 in the White Mountains, Inyo Co, California. We tested six predictions regarding the effect of food on the population size, reproduction, and movements of mice. Overall, the addition of food to three of six trapping grids resulted in (1) no treatment effect on the population sizes of pinyon mice; (2) larger numbers of new adult mice (i.e., immigrants) on treatment grids the first year; (3) no effect on reproductive activity of pinyon mice; (4) no effect on concentrations of reproductive hormones or masses of mice; (5) no effect on distances moved between telemetry loci; and (6) no evidence of larger home ranges on control grids than treatment grids. We conclude that pinyon mice were not food-limited during our study, but that food did somewhat influence population dynamics. Based on data showing natural population highs in 1993, we suggest that our distribution of feeder boxes may have provided concentrated and stable food patches that caused adult pinyon mice to defend the resources, and keep population sizes reduced.