Assessing Bridge Characteristics for Use and Importance as Roosting Habitats for Bats, November 2018

Bats play an important role in the natural balance of many ecosystems. As a result, there has been a growing concern about the number and status of bats in the US and beyond. Concern over bat populations is primarily driven by the fact that habitats used by bats for roosting and foraging have been disturbed, altered, or reduced. In Iowa, at least one federal endangered bat is known to exist and thought to be potentially impacted by habitat influences. Conservation efforts targeted toward bats can be hampered by a lack of information on their habitats and usage. Although it is widely accepted that bats use bridges as roosting sites, little attention has been given to understanding the combined bridge and location characteristics associated with their use of bridges as roosting sites. Therefore, it is important to investigate how, why, and when bats use bridges as roosting sites. A major goal for this study was to better understand when bridge replacement/repair/ rehabilitation projects have the potential for “taking” (i.e., harassing, injuring, or killing) bat species that have been identified as federally threatened or endangered bat species. The primary objective of this work was to better understand what type of bridges (based on bridge characteristics including local topography and habitat availability) are the most likely to be used by bats as roosting locations. The study also aimed to document the means and methods developed and followed to conduct this work so that the evaluation protocol can be used by other states/regions. The findings showed that bridge characteristics, combined with land cover and bat species distribution data, can help identify locations with higher probabilities of bat roosting. This information can be useful to transportation agencies as they plan bridge replacement/repair/rehabilitation projects and can help conservation efforts targeted toward bats