Assessing site occupancy of Mohave ground squirrels: Implications for conservation

Abstract

ABSTRACTTo better understand the distribution and habitat relationships of the Mohave ground squirrel (Xerospermophilus mohavensis), a California state threatened species, I investigated site occupancy of squirrels using remote‐sensing wildlife cameras (i.e., camera traps). In 2012, I conducted camera trap surveys at 96 randomly selected sites within and adjacent to the Desert Tortoise Research Natural Area, in the western Mojave Desert, California. In 1,105 camera trap days, there were 91 detections of squirrels at 30 out of 96 sites. I used single‐season, single‐species occupancy models to explore several survey and site variables hypothesized to influence detection probability (p) and site occupancy (ψ) of the species. Detection probability of squirrels varied with survey date and between 2 study areas, peaking in early April (p = 0.23, SE = 0.05 and p = 0.13, SE = 0.05, respectively) but decreasing approximately 4‐fold by the end of the study season in mid‐May. Site occupancy was positively related to the length of ephemeral stream channel(s) within a site, increasing from 0.24 (SE = 0.07) to 0.89 (SE = 0.10) with the range of stream channel lengths observed. Vegetation transects conducted at the study sites in 2014 indicated higher percent canopy cover, species richness, and diversity of perennial shrubs along ephemeral stream channels than in the surrounding upland habitat. This study provides the first estimates of site occupancy and detection probability of Mohave ground squirrels using the non‐invasive method of camera trapping. The findings have implications for design and timing of future studies, and highlight the importance of protecting ephemeral stream channels for Mohave ground squirrel conservation. © 2015 The Wildlife Society.