A COMPARISON OF SMALL-MAMMAL COMMUNITIES IN A DESERT RIPARIAN FLOODPLAIN

We compared small-mammal communities between inactive floodplain and a ctively flooded terraces of riparian habitat in the Verde Valley of ce ntral Arizona. We used species diversity, abundance, weight of adult m ales, number of juveniles, number of reproductively active individuals , longevity, residency status, and patterns of microhabitat use to com pare the two communities. Although abundances of small mammals tended to be higher in the active floodplain, species diversity was greater i n the inactive floodplain. Results were inconsistent with our initial prediction that actively flooded riparian habitat acts as a species so urce, whereas inactive floodplain acts as a sink or dispersal site for small mammals. Within each habitat type, we found evidence of signifi cant microhabitat separation among the three most abundant small-mamma l species (Peromyscus boylii, P. eremicus, and Neotoma albigula). Perc ent cover by annual and perennial grasses and shrubs, substrate, and f requency of shrubs, trees, and debris were significant determinants of small-mammal distribution within a habitat type. We found that the th ree most abundant species selected a nonrandom subset of available hab itat. Nonrandom use of habitat and microhabitat separation were the tw o most important mechanisms structuring small-mammal communities in ri parian habitat of central Arizona.