The continental United States hosts a diverse array of bat species vital to our ecosystems. However, several bat species are facing significant threats, including disease, habitat loss and human disturbance. Special attention has been given to cave-dwelling species impacted by white-nose syndrome, a deadly fungal disease. This article explains the protections in place for federally listed bats in the United States, with a focus on how project proponents can ensure compliance with the Endangered Species Act (ESA).
Listing Status
The ESA was enacted in 1973 in the United States to establish protection for species that are at risk of extinction, which are listed under the ESA as threatened or endangered. Under Section 7 of the ESA, projects that require a federal action are required to coordinate with the United States Fish & Wildlife Service (FWS) regarding the potential for a “take” (harass, harm, pursue, hunt, shoot, wound, kill, trap, capture or collect, or attempt to engage in any such conduct)1 of species within the project area. Projects that require a federal action are authorized, permitted, licensed, funded or being carried out by a federal agency in whole or in part.
Projects that do not require a federal action may still need to coordinate with FWS under Section 10 of the ESA to determine if an action is allowed or if an incidental take permit will be required. Note that coordination is not required under Section 10, but the responsibility is on project proponents to ensure compliance. Any violations of the ESA are punishable by law and can result in civil and criminal penalties.
While this article focuses on federal regulations, many states have additional protections in place for bats. Consulting with state agencies is essential to ensure compliance with all laws.
Several bat species are listed or proposed to be listed under the ESA. Four species cover a large area of the continental United States, and their associated conservation measures have significant implications for development processes, as well as the maintenance of transportation and utility infrastructure. The Indiana bat (IBat), northern long-eared bat (NLEB) and gray bat (GBat) are listed as endangered. On September 13, 2022, the FWS announced a proposal to list the tricolored bat (TCB) as endangered, but the current timing for the final listing is unknown.
For any federally listed species whose range mapping intersects with a project’s action area (Figure 1), projects must determine if a site contains suitable habitat for any species on their species list. This will enable project proponents to understand if their project activities are likely to adversely affect the listed species. If regulatory agencies agree that a project site does not have a suitable habitat and activities will not affect the species, conservation measures will not be needed.
Suitable Habitat
In general, the presence of trees or manmade structures (including bridges and culverts) will indicate potentially suitable summer habitat for bats. Suitable summer habitat is described further in this article for each species, as there are slight differences.
Suitable winter habitat is also important to identify in a project area. Sites with karst geology (e.g., caves and sinkholes) may provide suitable winter habitat. If a project falls within any hibernacula buffers such as caves or mines where bats will hibernate over the winter, as mapped by the FWS or a state agency, more restrictions may be imposed.
Indiana Bat (Myotis Sodalis)
Suitable summer habitat for IBat includes forests and woodlots containing potential roosts (i.e., live trees and/or snags less than or equal to 5 inches [12.7 cm] at diameter breast height [dbh] that have exfoliating bark, cracks, crevices and/or hollows), as well as linear features such as fencerows, riparian forests and other wooded corridors.
IBats also roost in human-made structures, such as bridges and bat houses (artificial roost structures); therefore, these structures should also be considered potential summer habitats.
Northern Long-Eared Bat (Myotis septentrionali)
Suitable summer habitat for the NLEB includes forests and woodlots containing potential roosts (i.e., live trees and/or snags less than or equal to 3 inches [7.6 cm] dbh that have exfoliating bark, cracks, crevices and/or cavities), as well as linear features such as fencerows, riparian forests and other wooded corridors.
The NLEB also roosts (although to a lesser degree than forested habitat) in human-made structures such as buildings, barns, bridges and bat houses. These structures should also be considered potential summer habitat.
Gray Bat (Myotis grisescens)
GBats occupy caves or cave-like structures year-round. While gray bats prefer caves, summer colonies have been documented using dams, mines, quarries, concrete box culverts and the undersides of bridges. Most gray bats roost in as few as 15 major hibernacula; therefore, any impact to any one of the hibernacula could result in the loss of a significant amount of roosting habitat or bats. Of these four bat species, this species is the only one that does not use forested areas/trees for roosting.
Tricolored Bat (Perimyotis Subflavus)
Suitable TCB summer habitat includes forests, woodlots and linear features (e.g., fencerows and riparian corridors) containing trees with potential roost substrate (e.g., live and dead leaf clusters of live and recently dead deciduous trees, Spanish moss [Tillandsia usneoides] and beard lichen [Usnea trichodea]).
TCBs also roost in human-made structures, such as bridges and culverts, and occasionally in barns or the underside of open-sided shelters, like porches and pavilions. These structures should also be considered potential summer habitat.
Conservation Measures
Because trees provide a suitable summer habitat for federally protected bats during their breeding season, the FWS has implemented restrictions for tree-clearing activities as a conservation measure for IBat, NLEB and TCB. Time of year restrictions (TOYRs) vary depending on the region, particularly if bats are present year-round. Notably, TOYRs focus on seasons when the bat is out of hibernation and present in a suitable summer habitat or, most importantly, during the pup season. The seasons can be accessed from Appendix L: Bat Activity Table of the FWS Indiana Bat and Northern Long-Eared Bat Survey Guidelines.2
Conservation measures for winter suitable habitat include reduced activity near known hibernacula. Coordination with the local FWS Field Office (FO) is needed to determine the necessary measures for a specific project.
Surveys and Habitat Assessments
Qualified biologists can conduct surveys to assess the presence of suitable habitat and bat activity in the project area (Figure 2). Approved surveyor lists are publicly available online for each local FO. Note that the FWS Indiana Bat and Northern Long-Eared Bat Survey Guidelines outline how and when to perform presence/absence surveys (acoustic or mist-net), hibernacula assessments, emergence surveys and bridge/culvert assessments, which may be necessary to understand which conservation measures are appropriate for projects. Note that surveyors must be approved by FWS, and there are specific windows during which surveys may be conducted. All results are subject to FWS approval.
Conclusion
The FWS has established bat protection measures that require collaboration between project developers, biologists and the FWS. Coordination early in the planning process and throughout the project stages is crucial so regulators and project proponents can assess the potential for suitable habitat, agree on potential impacts and develop mitigation strategies. By understanding the legal requirements and appropriate conservation measures, project proponents can ensure their activities comply with the ESA and minimize impacts on bat populations.
The future of bat conservation depends on ongoing research, habitat protection and public education. By working together, these vital ecological contributors can be safeguarded for generations to come.
References
- United States. (1983). The Endangered Species Act as amended by Public Law 97-304 (the Endangered Species Act amendments of 1982). Section 3(19). Washington: U.S. G.P.O. fws.gov/laws/endangered-species-act/section-3.
- U.S. Fish and Wildlife Service. 2024. Range-wide Indiana Bat and Northern Long-eared Bat Survey Guidelines. U.S. Fish and Wildlife Service, Region 3, Bloomington, MN. fws.gov/media/range-wide-indiana-bat-and-northern-long-eared-bat-survey-guidelines.
About the Experts
- Ellyse Marques, WPIT, project regulatory specialist, Wetland Studies and Solutions, Inc., a Davey Company, is on the Virginia Field Office’s Approved Surveyor List for acoustic surveys. She coordinates projects with federal, state and local regulatory staff to ensure compliance with endangered species, wetland and other protections.
- Alison Robinson, PWS, PWD, VSWD, CT, senior associate environmental scientist, Wetland Studies and Solutions, Inc., a Davey Company, coordinates bat habitat evaluations and acoustic surveys across the Mid-Atlantic. Her expertise also includes wetland delineation, mitigation banking monitoring and natural resource inventories.
