Hoary bat data aggregation and range mapping

Bringing together the best available data for hoary bats in California and beyond

Hoary bats are a migratory tree-dwelling bat species that occur across much of North America. Unfortunately, they have been negatively impacted by renewable energy development, among other factores. To help support the development of best management plans that reduce the risks of renewable energy development to hoary bat populations in California, the California Department of Fish & Wildlife (CDFW) needs to collate the best available data describing the presence of this species across California and have a range map that helps identify where this species may be present at various points in the season.

Because bats are nocturnal and primarily active at night, one of the primary ways to determine where they occur is to use acousting monitoring. This involves placing bat detectors in possible bat habitat for one or more nights, and then processing recorded audio data to identify likely detections of bat species. The Bat Acoustic Monitoring Portal (BatAMP) in Data Basin provides a platform where bat researchers can then upload records of bat species that they have detected using acoustic monitoring. I developed the BatAMP Visualization Tool during my tenure with the Conservation Biology Institute, in partnership with the the USDA Forest Service (USFS), as a way to better explore and visualize these acoustic records over time and space.

The North American Bat Monitoring Program (NABat) is a research platform that aggregates observations on bat species using a variety of methods, including stationary and mobile acoustic detectors, roost site monitoring, population surveys, and capture records. The goal is to use standardized data collection methods to create a continental-scale synthesis of bat occupancy and trends. Historically, NABat acoustic monitoring data was focused on the summer active period, which meant that acoustic bat monitoring data for other seasons were typically uploaded to BatAMP instead.

In this project, we are collaborating closely with bat scientists in the USFS and CDFW to aggregate acoustic monitoring data from both BatAMP and NABat into a standardized dataset that can be used to explore bat occurrence over time across North America. This will enable them to better understand the seasonal distribution patterns of hoary bats throughout California and inform the creation of seasonal habitat maps.

Because the same original data may be uploaded to both BatAMP and NABat, but in slightly different ways, a significant part of the project involves de-duplicating records to help avoid double-counting observations. Both data sources are currently being aggregated together to integrate into the BatAMP Visualization Tool, which will be a primary tool for members of the project and broader bat monitoring community to explore these data.

We will also be integrating CDFW’s capture records and radio-tagged bat detections to help supplement the available occurrence data for hoary bats. Whereas acoustic detections indicate the likely detection of particular species, they are subject to error. In contrast, both the capture records and radio-tagged bat detections provide high confidence observations of hoary bats at a particular location and time.