Is patch use determined by fine-scale microhabitat differences or density dependent habitat selection?

Abstract

If individuals base their patch and habitat choices on fine-scale differences in microhabitat, then their use o f patches, defined by capture sites, should correspond with measures o f microhabitat. But if individuals assess and respond to habitat at larger spatial scales, then site use should correspond with habitat selection at those scales. I tested these predictions by monitoring the distribution of meadow voles (Microtus pennsylvanicus) in 0.25ha old-field enclosures in northern Ontario, Canada (the Lakehead University Habitron). I varied the population density in two pairs of adjacent enclosures and tested for habitat selection with habitat isodars. Three of four isodars were statistically significant, but even so, meadow voles were vague density-dependent habitat selectors. The use of capture sites was related to microhabitat only in the one case where isodars failed to detect density-dependent habitat selection. Otherwise, site use was related to the number of animals living in paired enclosures. Site use by meadow voles was determined primarily by density-dependent habitat selection.