Talk Brandenbark™: Mitigation/Management tool for projects involving bark roostings bats

Multiple imperiled bat species around the world utilize trees with exfoliating bark for warm season roosting.  Impacts to this roosting habitat are a concern for transportation projects that occur within the range of a protected species.  Disturbance to roosts of protected species can require avoidance, minimization, and mitigation strategies.  Current mitigation strategies for impacts to summer habitat of bark roosting bats are not readily available, often ineffective and unproven, and can be cost prohibitive.  BrandenBark™ is an artificial roost structure developed to mimic the natural habitat of bark roosting bats.  It has been shown to be an effective artificial roost for six species of bats, including the U.S. federally endangered Indiana bat (Myotis sodalis) and other bat species that utilize bark roosts.  BrandenBark™ structures at the study site (Fort Knox, Kentucky, USA) have been utilized to provide habitat for Indiana bats within the range of a known maternity colony and have been placed in locations typical for Indiana bat primary roost trees.    During the study period (2012-2015), BrandenBark™ structures were selected by Indiana bats regularly with 77.2% (186 of 241) of roost visits documenting occupation and 72.7% (16 of 22) BrandenBark™ structures displaying signs of bat use within three months of installation.  Pre-volancy emergence counts (May through June, n=45) of 10 BrandenBark™ structures documented an average maximum emergence count of 92 bats, comparing favorably to the average adult maternity colony size of 80 female bats.  Post-volancy emergence counts (July through August, n=47) of 11 BrandenBark™ structures documented an average maximum emergence count of 122 bats.  Previous field studies have resulted in a post-volancy average maximum emergence count of 119 bats exiting from natural tree roosts.  BrandenBark™ also resulted in the second highest Indiana bat maternity emergence count recorded from a single roost with 451 bats.  The highest being 475 bats emerging from a natural tree.  Radio tracking and mist netting has resulted in documentation of Indiana bat use of 13 BrandenBark™ structures for a total of 248 bat days.  The roost area under BrandenBark™ is slightly warmer (= 24.6±7.2 [SD]°C) than that of natural bark (= 23.1±6.5°C).  Temperature differences between BrandenBark™ and ambient (= 2.1±2.7°C) are less variable than the temperature difference between natural bark and ambient (= 3.9±4.0°C), possibly indicating a more stable thermal environment.  In addition to being proven at the study site, BrandenBark™ has been deployed as a mitigation/land management tool by a number of transportation, natural gas, and wildlife conservation proponents to provide immediate roosting habitat for imperiled bark roosting species.  To date, 127 BrandenBark™ structures have been installed in eight U.S. states and one Canadian province.  BrandenBark™ provides instant long-lasting habitat commensurate with natural roosts, is easy to install and monitor, and does not require the purchase of additional land for placement when used as a mitigation option.

bat; mitigation; artificial bark; Indiana bat