The effects of interspecies interactions and human disturbances on wildlife in highway underpasses

Molly R. Caldwell, California Department of Fish and Wildlife
Mario Klip, California Department of Fish and Wildlife
Topic Area
Terrestrial Wildlife and Ecosystem Interactions with Transportation

Highway underpasses aim to provide wildlife safe passages under roadways. As enclosed travel corridors, underpasses facilitate close interactions between species, including humans. Despite likely predator-prey dynamics and human avoidance patterns by wildlife, there is limited research on interspecies interactions within these corridors. Three underpasses in Hallelujah Junction Wildlife Area, Sierra County, California, are used by wildlife including mule deer (Odocoileus hemionus), mountain lions (Puma concolor), coyote (Canis latrans), bobcat (Lynx rufus), and various rodents and lagomorphs. The habitat of the area is composed of sagebrush scrub, bitterbrush, and juniper woodlands. Camera traps were deployed on each side of the underpasses to understand wildlife usage. Data was collected from June 2017 to December 2018 with 3,584 total detections of wildlife. The objective was to determine whether interspecies interactions and human disturbances influence wildlife traveling through the underpasses on a spatial and temporal scale. Using single-species occupancy models, we calculated species' detection probabilities for each camera site with species' detection rates and human disturbances (human, cattle and ATV detection rates) as covariates. Additionally, species' daily activity patterns were estimated using kernel density functions and the amount of overlap between species' temporal activity patterns was calculated. The occupancy models provided evidence that mule deer avoided camera sites with higher mountain lion detections (p < 0.001). Coyotes were more likely to be detected at sites with higher rodent and lagomorph detections (p < 0.001). Additionally, coyotes avoided sites with higher human disturbances (p < 0.01). The estimates of daily activity overlaps showed mountain lions following mule deer activity patterns temporally. The overlaps also showed temporal avoidance between bobcats and coyotes, rodents/lagomorphs and their predators, and mountain lions and humans. The results found indicate that predator-prey interactions and human disturbances can have a considerable effect on the spatial and temporal patterns of wildlife in underpasses.

Abstract Keywords
Highway Underpasses
Interspecies Interactions
Human Disturbances