Human activities influence mule deer use of overpasses across multiple scales

Abstract

Anthropogenic linear infrastructures (ALIs), including roads, railways, and canals, provide important resources to humans, but they can affect wildlife through habitat fragmentation and reduced movement through landscapes. To mitigate these effects, overpass crossing structures (i.e., overpasses) can facilitate wildlife movement across ALIs and maintain landscape connectivity. Human activities can potentially influence spatial and temporal patterns in wildlife use of overpasses; however, little information is available about human–wildlife interactions across some types of ALIs. Using remote wildlife cameras, we evaluated human and mule deer (Odocoileus hemionus) use and interactions at 43 overpasses along the Central Arizona Project canal in Arizona, USA, during 2 seasons (warm and cool) from February 2021 to February 2022. Mule deer exhibited spatial avoidance of human activities at overpasses, although the effect varied across seasons and types of human activity. At a broad scale, the presence of recreationists at overpasses did not exclude mule deer from using overpasses to cross the canal; however, human presence reduced mule deer detection probability in the warm season. At a fine scale, mule deer decreased use of overpasses as activity associated with canal personnel (i.e., security and maintenance workers) increased in the cool season. For both seasons, mule deer exhibited greater overlap in daily activity patterns with recreationists compared to canal personnel. Further, mule deer shifted daily activity patterns to be more active earlier in the morning at sites with high amounts of recreational use compared to sites with lower recreational use. Because human activities can influence mule deer crossings at overpasses, managers might consider minimizing human activities at crossing locations to increase wildlife use and promote wildlife movement across canals and other types of ALIs.