Most Likely Bridges as Roosting Habitat for Bats: Study for Iowa

Abstract

Bats play an important role in the natural balance of many ecosystems. There has been a growing concern about the bat population in the United States, mainly because of white-nose syndrome (WNS). The primary objective of this work was to better understand what types of bridges are the most likely to be used by bats as roosting locations. In one of the most comprehensive studies in the United States to date, 517 structures in the state of Iowa were inspected for evidence of bat roosting. Logistic regression models were fitted to identify structure, land cover distribution, and predicted bat species distribution characteristics that increase the probability of bat roosting. The final model indicated that probability of bat roosting on bridges increases under the following conditions: structures are prestressed concrete continuous, prestressed concrete or steel continuous; increased superstructure height above ground; increased superstructure depth; increased wetland coverage within a 0.1-mile radius of the structure; and increased number of potential bat species present at the location. The findings show that bridge characteristics, combined with land cover and bat species distribution data, are significant for higher probabilities of bat roosting. This information can be useful to transportation agencies as they plan bridge maintenance and renewal and can also help conservation efforts targeted toward bats. It is thought that the integration of objective, geospatial land cover data with potential bat presence data, and estimation of quantitative and relative influence of variables on probability of bat roosting are unique to this study.

Wildlife Use of Anthropogenic Structures: A Comprehensive Review of Bridge Use by Bats

“…Researchers in Montana examined 2,076 bridges maintained by the Montana Department of Transportation (MDOT) and US Forest Service and found 35–50% of bridges surveyed were used as night roosts, and 0.5–10% as day roosts across 52/56 counties (Bachen and McEwan, 2019). In Iowa, 124 of 517 structures (24%) had documented bat presence across the state (Bektaş et al ., 2018). Nearly three hundred bridges were randomly selected in Florida where 16 (5.4%) contained bats (Gore and Studenroth, 2005).…”

“…Beam and girder style bridges with open expansion joints (Fig. 4) are used as day roosts more than any other design of bridge due to the presence of numerous crevices (Davis and Cockrum, 1963; Keeley and Tuttle, 1999; Adam and Hayes, 2000; Lance et al ., 2001; Feldhamer et al ., 2003; Keeley and Keeley, 2004; Gore and Studenroth, 2005; Bektaş et al ., 2018; Meierhofer et al ., 2018; Bachen and McEwan, 2019; Etchison and Weber, 2020). Cast-in-place bridges are sometimes used by bats if the hollow interior of the structure is accessible, or if gaps are present between expansion joints (Davis and Cockrum, 1963; Keeley and Tuttle, 1999; Lance et al ., 2001; Feldhamer et al ., 2003; Keeley and Keeley, 2004; Bachen and McEwan, 2019).…”

Use of Ultrasonic Acoustic Technology for Temporary Deterrence of Bats from Bridges

“…White-Nose Syndrome (WNS) is estimated to have killed more than 5.7 million bats in eastern North America since it was identified in New York in 2006 (1). As a result of WNS and increased disturbance of habitats used by bats for roosting and foraging, there has been a growing concern about the bat population in the US in the last decade.…”

“…During the summer months, bat species have been known to utilize bridges as daytime roosting habitats and may also use them as places to form maternity colonies where they give birth and raise their young (1)(2)(3)(4)(5)(6)(7). Bridge repair and replacement projects are required to follow additional regulatory requirements to avoid and minimize impacts to bats, when protected bat species are present on bridges.…”

Deep Learning-Based Visual Identification of Signs of Bat Presence in Bridge Infrastructure Images: A Transfer Learning Approach

“…Researchers have designed field studies with biologists and engineers to determine the extent to which bats are using highway infrastructures and their roosting preferences, and developing methods that predict bat usage (11,(13)(14)(15)(16). A national survey was conducted including more than 2,000 bridges to study bat usage of bridges (11).…”