Use of underground facilities by bats at the Hanford Site in shrub-steppe habitats in Washington

Jonathan Guy Lucas

Wildlife habitat conservation on military and other large publically owned landscapes is widely recognized as critical in the United States given continuing human population growth, increasing intensity of land use, and the large number of threatened and endangered species occupying these lands. The Department of Energy's, Hanford Site, in south central Washington, was established in 1943 for atomic bomb material production during World War II. The Hanford Site encompasses 1517 km2 (151,773 ha) of shrub-steppe landscape and now represents one of the largest blocks of such habitat in Washington. Plutonium production ended at the Hanford Site in the late 1980's and contaminant remediation began in 1989. As part of this long-term cleanup and shutdown process, we studied two sites with bat colonies (183-F clearwell and the190-D/DR process water tunnels) to determine the extent of bat use of constructed facilities (e.g., buildings, underground tanks and tunnels), scheduled for removal or closure. We conducted mist-netting, acoustic monitoring, infrared (IR) videotaping, and visual surveys from August 2007 to August 2010 to determine the potential importance of constructed facilities to regional bat populations. Approximately 3600 bats were discovered at 183-F, while about 340 bats were found at the 190-D/DR water tunnel, with each site containing maternity colonies. Genetic analysis of wing punch tissue from both colonies indicated the presence of Yuma myotis (Myotis yumanensis) and revealed ten overlapping matrilines between the two colonies, but no significant difference in their frequencies. Acoustic monitoring at 183-F indicated spring and summer maternity activity started to increase about mid-March. Surprisingly, some acoustic calls were recorded through fall and winter, with calls still being recorded down to minimum air temperatures of 13.8 0 C (7.1 0 F), indicating that not all individuals left the Hanford Site during winter. The 183-F clearwell is the largest known maternity colony of Yuma myotis (Myotis yumanensis) in Washington State and demonstrates the importance of assessing artificial structures potentially slated for removal or modification to assess their ecological importance for western bat species. Consequently, the 183-F structure was saved from potential future demolition and remains an important resource supporting regional bat populations.

Use of underground facilities by bats at the Hanford Site in shrub-steppe habitats in Washington

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