Responses of mice to fluctuating habitat quality I. Patterns from a long-term observational study
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We determined intra- and interspecific patterns of habitat selection of mice living in an environment with a simple, but extremely variable resource base: the pinyon (Pinus monophylla)-juniper (Juniperus monosperma) woodland of the western Great Basin. Although numbers of deer mice (Peromyscus maniculatus) and pinyon mice (P. truei) showed similar responses to variations in resource abundance, the timing and age-related composition of this response in deer mice differed markedly from that in pinyon mice. Pinyon mice were resident on our study grids, but deer mice migrated onto the grids in response to a heavy pinyon cone crop. There were more significant correlations in intraspecific (sex-age) abundance in low cone years than in high cone years, and there was a moderate negative correlation between subadult and adult female pinyon mice during high cone years. There was an overall pattern for both Peromyscus species of fewer and weaker correlations between abundances and habitat characteristics during low cone years. During high cone years both fall and winter breeding activity was evident, and pinyon mice showed a three-fold higher rate of winter breeding than deer mice. All age classes of pinyon mice and deer mice showed a trend of higher between-season residency during low cone years. We conclude that different models of habitat selection operate dependent on the sex-age segment of the population, season, and quantity and quality of the resource base.