The Influence of Visitors, Habitat, and Methodology on Mexican Spotted Owl (Strik occidentalis lucida) Occupancy and Detection in a Remote Canyon Environment
Date of Final Oral Examination (Defense)
Type of Culminating Activity
Master of Science in Raptor Biology
Jen Cruz, Ph.D.
Jim Belthoff, Ph.D.
Jesse Barber, Ph.D.
National Parks across America play an important role in protecting natural resources and providing access to recreation for visitors. However, these goals may come into conflict as visitation rates rise. Grand Canyon National Park in Northern Arizona is one of the most highly visited parks in the United States, with over 6 million visitors a year. Backcountry hiking and camping are popular activities in the park, and many highly visited hiking trails and campgrounds overlap with known breeding areas of a threatened species, Mexican Spotted Owl. In this thesis, I explore the intersection of recreation and wildlife conservation at this popular park through the lens of long-term occupancy of a threatened species. My aims are to (1) assess the potential impact of visitor use on long-term occupancy (2001 to 2021) of Mexican Spotted Owls at the Grand Canyon, and (2) evaluate the potential for autonomous recording units (ARUs) to complement current survey protocols. To assess long-term occupancy, I ran a multi-season occupancy model using 20-years of call-back survey data conducted in protected activity centers (PACs), along with measures of visitor use and habitat characteristics. To assess the use of ARUs, I ran a single-season occupancy model using three years of data, which was collected using autonomous recording units in PACs from 2019 to 2021. I found that visitor use in the Grand Canyon had no effect on owl occupancy, which remained stable across PACs over the 20-year study period. Owl occupancy remained high across the 20-year survey period and was strongly informed by habitat characteristics. Specifically, Mexican Spotted Owls occupied PACs with higher proportions of mixed shrubland habitat and Supai formation. Conversely, owl occupancy decreased in PACs with more pinyon-juniper woodland habitat and Redwall Limestone. Assessing the use of ARUs as a complement to current protocol, ARUs were found to be a useful tool for supplementing traditional call-back surveys, particularly at PACs with extremely limited access. In particular, ARUs detected Mexican Spotted Owls with high probability early in the breeding season prior to the official call-back survey period, which allows managers to extend their monitoring period. In highly remote PACs, ARUs were more suitable than call-backs because they could collect more data with less effort. Incorporating this method into Spotted Owl survey protocol may be essential for improving monitoring of under-sampled locations, which is a critical component for assessing long-term trends for this species across its range.
Fuller, Kirsten, "The Influence of Visitors, Habitat, and Methodology on Mexican Spotted Owl (Strik occidentalis lucida) Occupancy and Detection in a Remote Canyon Environment" (2022). Boise State University Theses and Dissertations. 2020.