Graduation Date

Spring 2021

Document Type



Master of Science degree with a major in Biology

Committee Chair Name

Dr. Joseph M. Szewczak

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Stephen C. Sillett

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Dr. C. John Ralph

Third Committee Member Affiliation

Community Member or Outside Professional

Fourth Committee Member Name

Theodore J. Weller

Fourth Committee Member Affiliation

Community Member or Outside Professional

Subject Categories



Loss of roosting resources, either through disturbance or removal, negatively affects bats. For sensitive species, such as the Townsend’s big-eared bat (Corynorhinus townsendii), determining roost requirements is a critical component in conserving their habitat. Such cavity roosting bats on the North Coast of California may use hollows in large redwood trees. In this study, I 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 using hollows by analysis of DNA in guano. Analysis of environmental DNA from soil was attempted, but failed. Of 253 species identifications from 83 hollows, the most prevalent were Myotis californicus (28.5% of all identifications), the Myotis evotis-Myotis thysanodes group (17.4%), C. townsendii (17.0%), and Myotis volans (15.0%). Guano production peaked in summer months at all study sites. I evaluated the extent to which habitat variables at the scales of the hollow, vicinity, and site influenced the level of roost use. Multiple regression was used to examine correlations between guano mass and habitat variables, and logistic regression was used to determine which habitat variables were important to C. townsendii. At the hollow scale, guano mass increased with height of the ceiling above the opening. Corynorhinus townsendii selected for large hollow diameters, low ground height, and high ceilings above the hollow 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 other nearby hollows. These tree hollow roost preferences can inform land managers when planning conservation and management of redwood forests.

Citation Style

Journal of Wildlife Management


Thesis/Project Location