Graduation Date
Spring 2021
Document Type
Thesis
Program
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
Biology
Abstract
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
Recommended Citation
Armstrong, Amon Jotesh, "Use of redwood basal hollows by bats: a focus on the Townsend's big-eared bat on the North Coast of California" (2021). Cal Poly Humboldt theses and projects. 491.
https://digitalcommons.humboldt.edu/etd/491
Included in
Forest Management Commons, Other Ecology and Evolutionary Biology Commons, Zoology Commons