Wildlife use of overpass and underpass crossings along the Central Arizona Project canal, Arizona

Anthropogenic linear infrastructures, including roads, railways, and canals, provide important resources to humans. However, linear infrastructures can reduce landscape connectivity for many wildlife populations. To mitigate these effects, crossing structures and crossing areas can facilitate animal movement across linear infrastructures. Compared to roads, little research has evaluated the factors influencing wildlife use of crossings along major canals. The Central Arizona Project (CAP) canal is a major linear feature in Arizona, and exhibits multiple types of crossing structures and areas. In Chapter 1, the objective was to evaluate the spatial (i.e., landscape features, crossing attributes) and temporal (i.e., season, time of day) factors influencing wildlife use of overpasses (n = 43) and siphons (n = 13) along the CAP canal. Using remote wildlife cameras, 17 species were detected using overpasses and siphons along the CAP canal during one year. Animals exhibited species-specific preferences for landscape features, such as topography and vegetation, and canal crossing types, although many species decreased use of overpasses associated with human development. In Chapter 2, the objective was to evaluate the influence of human activities at overpasses on use by mule deer across multiple analytical scales. Mule deer occupancy and relative habitat use at overpasses decreased in relation to human activity, including recreation. In Chapter 3, the objective was to evaluate seasonal use of underpasses (n = 12) by mammals, reptiles, amphibians, and invertebrates. Using specialized remote wildlife cameras, 30 species were detected using underpasses along the CAP canal across three seasons, and some animals exhibited variable crossing frequencies in relation to the summer monsoon season. Overall in this project, several species of small to large-sized mammals, reptiles, amphibians, and invertebrates used a variety of crossing types, including overpasses and underpasses, along a major canal. Ultimately, this study suggests that to promote landscape connectivity for the wildlife community associated with canals and other types of linear infrastructures, it is important to provide a variety of crossing types that occur across a range of landscape characteristics.