Bat Avoidance, Exclusion, and Mitigation

There has been an increase in awareness of declining bat populations across the U.S. Many of California’s agencies are increasing and standardizing their requirements for protecting bats and their roosts. Gallaway Enterprises has been closely following these changes and responding by implementing scientifically appropriate and creative solutions for bat avoidance, exclusion, and mitigation techniques. Gallaway Enterprises is using the latest version of SonoBat acoustic bat detection software to aid in the process of identifying which bat species are present at many of our project sites. SonoBat software can determine species by analyzing calls that have been recorded by our biologists.


Gallaway Enterprises bat specialists stayed busy in 2018 with several bridge replacement and retrofit projects that had large bat maternity colonies roosting within the bridges. Two particularly challenging projects this year were the East Hill Road over Davis Creek Bridge Replacement project in Mendocino County and the Mockingbird Road over Robinson Creek Bridge Replacement project in Lake County. Structure- or bridge-roosting bats were not identified as a species with potential to occur on either project, but were discovered incidentally by Gallaway Enterprises during pre-construction surveys. One bridge was home to a large maternity colony and the other was a bat bachelor roost. Working closely with the contractors, local agencies, and the California Department of Fish and Wildlife (CDFW), Gallaway Enterprises developed avoidance and minimization measures and a plan for temporary and permanent roost mitigation. For these projects, time was of the essence. Gallaway Enterprises worked quickly to develop the mitigation measures and start consultation with CDFW to ensure minimal construction delays. Measures developed were project-specific and included construction of noise attenuation devices, acoustic and visual monitoring during pile driving, visual disturbance buffers, and the installation of bat exclusion devices to safely and humanely evict bats outside of the maternity season. Gallaway Enterprises bats specialists conducted compliance monitoring and installed exclusion devices at the bridges during the appropriate exclusion windows.

Lastly, Gallaway Enterprises worked with stakeholders to design and construct bat roosting habitat that mimics the pre-project roost temperatures in order to attract a wide arrange of bat species to mitigate the loss of roosting habitat. Boxes were a mix of wooden and concrete design and were strategically mounted to the new bridge structures, as well as, poles around the sites.