An urban cast of characters: Landscape use and cover influencing mammal occupancy in an American midwestern city

Abstract

With future human population growth concentrating in urban areas, cities are working to counterbalance ecological disturbances resulting from development by incorporating green space that supports greater biodiversity. An initial line of inquiry into designing wildlife-inclusive green space involves evaluating landscapes that are associated with the habitat use of urban species. In this study, we utilized occupancy modeling to estimate select terrestrial mammal presence in a fast-growing mid-sized midwestern city to determine possible taxa-specific associations with multiple land use and cover variables, specifically those associated with higher degrees of human activity. Using motion-triggered infrared trail cameras over eight seasons from winter 2017 to fall 2018, we applied a single-species, single-season stacked design to estimate occupancy for eight urban dwelling mammals. Taxa-specific models contained one of three possible detection variables (null, percent green space, or percent impervious surface) and combinations of three species-specific variables, natural and anthropogenic. We hypothesized that large species, coyote (Canis latrans) and white-tailed deer (Odocoileus virginianus), would exhibit the most positive association to natural land cover and the most negative association to anthropogenic land cover. We also hypothesized that small and medium sized species, eastern cottontail (Sylvilagus floridanus), gray squirrel (Sciurus carolinensis), opossum (Didelphis virginiana), raccoon (Procyon lotor), red fox (Vulpes vulpes), and striped skunk (Mephitis mephitis), would demonstrate a neutral association to land cover type, anthropogenic or natural. Our results indicated that the presence of anthropogenic features rather than any particular natural land cover may be driving wildlife distribution in our study area, as none of our species demonstrated a positive association to natural land cover (percent recreation, residential yards, vacant land, or woodland). Species with a wide range of body sizes, showed a negative association with residential yards, indicating that this type of green space may be an unnecessary or unsuitable subsidizing resource in our study area. With our results in mind, we recommend increasing the amount of natural or less manicured green space to offset the intensity of impervious surface as well as encouraging the establishment of native vegetation in existing and newly constructed residential development to better connect urban green space and residential yards to larger adjoining tracts of natural landscapes. For our study area and other cities in similar phases of development, these suggestions may be essential first steps to reduce biodiversity loss and strengthen community ecology as urban areas continue to grow.