Bridges are an important resource for bat roost habitats in many states across the U.S., primarily due to increasing pressures from forest habitat loss, wildfire, and spread of white-nose syndrome. The Indiana bat and the northern long-eared bat are listed as Federally Endangered and Federally Threatened under the Endangered Species Act (ESA), respectively. Given requirements within the ESA, a better understanding of artificial bat roost designs, long-term maintenance needs, criteria for monitoring success, and best design practices is needed to guide mitigation decisions made by transportation professionals. Information is available on existing bridge designs and bat roost use and features. However, an analysis of transportation structures and site-specific factors that influence the performance of bat roost mitigation is needed.
The purpose of this research is to conduct an analysis of transportation structures and site-specific environmental factors that influence the performance of bat roost mitigation in order to inform best mitigation design practices, and to develop a manual of best design practices.
Task 1: Gather background data via lit review and interviews with key professionals on key microhabitat and site criteria that influence the use of on-site (bat houses installed within or mounted to bridge/box culvert structures) and offsite (standalone bat houses) artificial bat roosts. Cost information for design, construction, and maintenance of various mitigation designs will also be collected. The effects of recent developments in bridge design and construction methods upon bat roost mitigation designs will be described.
Task 2: Conduct a comparative performance analysis of bat roost designs comparing structure types, site-specific conditions, monitoring opportunities, and costs for typical mitigation goals (re-establishing colonies after construction, providing habitat for maternity colonies, providing evidence of occupancy for target species, any unique needs for threatened or endangered species).
Task 3: Prepare a Best Design Practices Manual that includes the results of Task 1, compilation of monitoring data, and the comparative performance analysis.