Abstract: Anthropogenic linear infrastructures (ALIs), including roads, railways, and canals, can reduce landscape connectivity for wildlife. However, overpass crossing structures can facilitate animal movement across ALIs. Landscape factors across multiple scales and crossing structure features can influence animal use of overpasses, which can also vary across seasons. Compared to roads, little research has evaluated how factors at multiple spatial scales influence wildlife use of overpasses on major canals. Our objective was to understand how landscape and structural factors influenced wildlife use of overpasses along the Central Arizona Project (CAP) canal across three seasons (i.e., the hot-dry, hot-wet, and cool-wet seasons) during one year. Remote wildlife cameras were maintained at 40 overpasses on the CAP canal. We used Poisson generalized linear mixed models to compare crossing rate of animals among three seasons, and we used Royle-Nichols models to evaluate relative use of overpasses across a suite of landscape factors (i.e., plant productivity, terrain, and human development at broad scales and vegetation cover at fine scales) and between two overpass types (i.e., wildlife bridges and concrete overchutes). We detected 16 small to large-sized mammal species using overpasses to cross the canal, and focus on four focal species (e.g., bobcat, coyote, mule deer, peccary) for this presentation. Crossing rate at overpasses was highest in the hot-dry season for three species. Animals exhibited species-specific relationships with landscape and structural factors. For example, large herbivores (i.e., collared peccary and mule deer) increased use of OCS associated with greater amounts of plant productivity at broad scales. Between OCS types, mule deer exhibited higher use of wider concrete overchutes compared to narrower wildlife bridges. However, medium-sized carnivores (i.e., coyote and bobcat) exhibited higher use of wildlife bridges. In addition, bobcats increased use of overpasses associated with fine-scale vegetation cover. Some herbivores and carnivores decreased use of OCS associated with human development. Overall, our study suggests that it is likely important to provide a variety of crossing types that occur across several different environmental gradients to promote use of canal crossings for a diversity of animals in the wildlife community.
