Abstract
We employed a live-trapping grid encompassing several discrete vegetation patches to analyze spatial differences in demographic structure of California voles ( Microtus californicus ). Densely populated patches had female-biased sex ratios, longer individual persistence of females, higher per individual productivity and emigration rates, and lower immigration rates than did sparsely populated patches. Male density was relatively constant among patches, while female density varied by a factor of three. The high degree of stability this population exhibited over the four years in which density was estimated may be a result of the presence of perpetually unfilled dispersal sinks. A laboratory study showed that demographic performance in a given patch is strongly associated with the dietary quality of the vegetation present in that patch. Vegetative cover may also be important in contributing to demographic differences among patches, but is less important than food. Because the quality of diet and, presumably, protective cover, had the same effect on both males and females, it appears that sex differences in response to habitat heterogeneity are a result of differences in spacing behavior.
Published Version
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