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Loss of roosting resources, either through disturbance or removal, negatively affects bats. Identifying sensitive species and determining roost requirements are critical components in conserving their habitat. Cavity roosting bats on the North Coast of California are known to use hollows in large redwood trees. In this study, we examined the factors determining the use of basal tree hollows by different bat species at eight redwood forest sites in Del Norte, Humboldt, and Mendocino Counties, California. Bat guano was collected from 179 basal hollow roosts from 2017 to 2018, and guano mass was used as an index of roosting activity. Nine bat species and one species group were identified by analysis of DNA in guano. Of 253 species identifications from 83 hollows, the most prevalent were Myotis californicus (California myotis; 28.5% of all identifications), the Myotis evotis-Myotis thysanodes group (17.4%), Corynorhinus townsendii (17.0%), and Myotis volans (15.0%). We evaluated the extent to which habitat variables at the scales of the hollow, vicinity, and site influenced the level of roost use. Correlations between guano mass and habitat variables were examined using multiple regression analyses. At the hollow scale, guano mass increased with ceiling height above the opening. At the vicinity scale, guano mass increased with less cover of small trees. At the site scale, there was no association between guano mass and distance to foraging areas, elevation, or number of nearby hollows. These tree hollow roost preferences can inform land managers when planning conservation and management of redwood forests.


Data in this repository were analyzed for my thesis and related publications. The data represent 1,547 guano collection visits, recorded as guano mass, at 131 basal hollows on the North Coast of California (Del Norte, Humboldt, Mendocino Counties) in 2017 and 2018. Hollow, vicinity, and site data are included as independent variables that were recorded once over the study period. Data collection methods are presented in the corresponding manuscript, available here: