RESPONSES OF SMALL MAMMAL COMMUNITIES TO FLOW RESTORATION AND VEGETATION ALONG THE SANTA CRUZ RIVER

Abstract

Release of treated effluent at stretches of a dewatered river can alter the water resources, vegetation, and small mammal communities found at them. Previous research on this subject is scarce and has primarily focused on comparisons of riparian and upland habitats adjacent to non-effluent-dependent rivers. We investigated the impacts of flow restoration and vegetation on small mammal communities along the Santa Cruz River in Tucson, Arizona. We surveyed a dry site along the river and a wet site where effluent is being released. Surveying was done through trapping small mammals along transects and recording vegetation and water data at each trap site. We evaluated how vegetation differed between the sites and how small mammal abundance, diversity, and habitat selection differed. Vegetation diversity was higher at the dry site than the wet site, and species were not found to use vegetation types uniformly. Small mammal species diversity was higher at the dry site than the wet site. However, capture abundance was much higher at the wet site than the dry site. These results suggest that river flow restoration through effluent release may benefit some small mammal species significantly more than others. Our study was limited by its sample size and the number of sites surveyed, so future studies should be done to present a more comprehensive picture of the relationship between flow restoration, vegetation, and small mammal communities.