Bat Habitat Acoustical Monitoring

Bat Habitat Assessment and Acoustical Monitoring Surveys

Marin County Parks proposed the construction of two bridges at Cascade Canyon Open Space Preserve to allow access across San Anselmo Creek during high winter flows. In order to estimate the bat species assemblage and activity levels prior to construction, Nomad conducted a habitat assessment and acoustical monitoring surveys during the summer breeding season of 2020 both at the proposed bridge sites and multiple additional locations within the Preserve. Through the assessment process Nomad was able to focus acoustical survey efforts on likely habitats, allowing the identification of species potentially rearing young within and in the vicinity of the Preserve.

Nomad deployed full-spectrum acoustical monitoring equipment in as many varied habitats as possible, focusing on likely flyways such as creek corridors, habitat edges, and potential roost locations. The resulting data were analyzed using the SonoBat software package, and auto-classified results were manually vetted to ensure accuracy of species identification.

The results indicated that a wide diversity of bat species occur within the Preserve, including one species that was detected outside of its generally known range. Nomad was able to use the results to make recommendations to Marin County Parks about bridge design characteristics while also documenting an inventory and relative abundance of bat species across the entire Preserve.

Nomad faced challenges in the field such as maintaining equipment security in public-access areas, battery life and data storage limitations, difficult access to optimal acoustical monitoring locations, and strict budgetary limitations. Working within these bounds, Nomad generated a robust dataset and delivered a high-quality report with sound results and actionable recommendations.

LOCATION: Cascade Canyon Open Space Preserve, Marin County, California
CLIENT: Marin County Parks and Open Space District

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