Bat use of old growth redwood basal hollows with increasing isolation in contiguous, remnant, and legacy forest stands
Graduation Date
2008
Document Type
Thesis
Program
Other
Program
Thesis (M.S.)--Humboldt State University, Natural Resources: Wildlife, 2008
Committee Chair Name
Matthew D. Johnson
Committee Chair Affiliation
HSU Faculty or Staff
Keywords
Legacy trees, hollow, Forest, Foraging resources, Patch fidelity, Remnant, old-growth, Roost, Chiroptera, Guano, Habitat, Intensity of roost use by bats, Bats, Old-growth redwoods, Hollow isolation, Roost selection, Humboldt State University -- Theses -- Wildlife, Basal hollow, Frequency of roost use by bats
Abstract
Roosting habitat is one of the most essential habitat components to consider for conservation of bat populations. Basal hollows found almost exclusively in old growth redwood trees provide a distinct roost type that has been recognized as a widely used resource by bats in the redwood region. With the estimated removal of more than 95 percent of old growth redwood trees, the distribution of these roost types has become increasingly limited. One possible outcome of lowered roost densities is a concentration of bats in basal hollows more geographically isolated from others. This study examined the effect of hollow isolation on forest-dwelling bat populations in Del Norte County in northern California. I compared the frequency and intensity of bat use of basal hollows within three hollow isolation categories: (1) contiguous forest stands with low hollow isolation levels; (2) small remnant forest stands with moderate hollow isolation levels; and (3) second and third growth commercial forest stands with high hollow isolation levels. Using monthly bat guano samples as an index of use, I found no evidence for increased use of the most isolated hollows. To the contrary, bats appeared to use less isolated hollows with greater frequency and equal intensity to those hollows in areas with higher isolation levels. Hollow internal volume, overhead volume relative to the hollow opening, and proximity to water were important variables in predicting which hollows would be used most. My results fail to support past findings in the same region that showed greater use by bats of basal hollows in isolated remnant forest patches than those hollows found in contiguous forested regions. Future studies should look at species composition of bats roosting within basal hollows, hollow temperatures, and available foraging resources for increased understanding of bats in redwood forests and those factors that influence roost selection.
Recommended Citation
Roberts, Amy, "Bat use of old growth redwood basal hollows with increasing isolation in contiguous, remnant, and legacy forest stands" (2008). Cal Poly Humboldt theses and projects. 1526.
https://digitalcommons.humboldt.edu/etd/1526
https://scholarworks.calstate.edu/concern/theses/1n79h681b