On Measuring Microhabitat Affinities with Special Reference to Small Mammals

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Abstract
Two different sampling regimes were used to measure microhabitat utilization patterns in animal communities. The more common one employs a completely random arrangement of sampling stations with respect to habitat structure, and microhabitat affinities are inferred from correlations between animal density at a station and habitat features present nearby. An alternative method employs a stratified random arrangement of sampling stations. Microhabitat categories are defined a priori, predetermined sampling effort is expended in each microhabiat, and affinities are inferred from relative frequency of occurrence in each microhabitat. Assumptions implicit in each method are discussed for 5 California [USA] coastal sage scrub rodent species [Dipodomys agilis, Perognathus fallax, Peromyscus maniculatus, P. eremicus, Neotoma lepida], microhabitat affinities obtained by the 2 methods are compared. Although there is some qualitative agreement between methods, the stratified random regime has several advantages over the other for studies of microhabitat affinity. For other sorts of study, a completely random design may be superior.