The relationship between habitat heterogeneity, space use, and demography in a population of California voles.

HIgh quality habitat patches (having high percent cover of the perennial grass Elymus triticoides) were characterized by higher peak densities of Microtus californicus, more strongly female- biased sex ratios, longer average persistence (= survivorship), and higher rates of juvenile recruitment than were lower quality patches (Conium maculatum and annual grasses). For females, probability of persistence varied markedly in response to seasonal (wet vs. dry) variation in resource quality, while for males, probability of persistence was lower and constant across all seasons. Persistence of females did not vary with population density, but persistence of males was inversely related to density. Females tended to aggregate in high quality areas but the distribution of males was more uniform. The responsiveness of females to both spatial and temporal variation in resource quality reflects a direct reliance on resource acquisition for reproductive success, and their tendency to overlap intrasexually indicates a lack of strong intrasexual interference. The lack of responsiveness of males to resource variation may reflect a relative independence from resource acquisition in seeking reproductive success, while their low co-occurrence and greater sensitivity to density variation indicates the presence of strong intrasexual interference.-from Authors