ABUNDANCE OF COTTONTAILS (SYLVILAGUS) IN AN EXURBANIZING SOUTHWESTERN SAVANNA

摘要

Ranches are being converted to low-density exurban housing developments in the Southwest, with potentially significant but little studied impacts on biological diversity. We counted cottontail rabbits (Sylvilagus audubonii and S. floridanus) in a grassland and in a mesquite-oak savanna in southeastern Arizona, on 48 plots evenly divided among landscapes that were grazed by livestock, or embedded in housing developments, or both, or neither. Cottontails were more abundant in exurban neighborhoods thanin undeveloped areas, independent of grazing. They also were more common on ungrazed than on grazed lands, independent of development. Counts were positively correlated with the number of homes near plots. Counts also were positively correlated with height of ground cover and percent tree canopy, but only among plots in undeveloped landscapes. These results are consistent with the hypothesis that cottontails benefited from exurban development because of increased cover provided by structures and landscaping, especially in areas such as open grasslands with relatively little natural cover.