Olsson Associates


A 'batty' dilemma

Thursday, April 24, 2014

Joan Darling, PhD, and Dane Peterson, Environmental Assessment

Bats—the winged, night-insect-eating warriors—have instigated both fear and admiration among many. But bats are in trouble. Their numbers are declining due to disease and loss of habitat, and they have become an important awareness component for many of the projects Olsson staff members have worked on.

In truth, bats are poorly understood by most people, primarily because we don’t see bats on a daily basis. Television and movies have provoked fear of them, but bats are common and very important to the ecosystem. Unfortunately, though, many improvement projects that benefit humans can negatively impact bats, as seen in a loss of bats’ habitats for roosting, foraging, drinking, or hibernating.

Bats are important to us because each one can consume around 1,000 insects per hour during the night. Throughout the United States, scientists have estimated that bats are worth more than $3.7 billion a year in reduced crop damage and pesticide use (Bat Conservation International).

While there are no laws specific to protecting bats, impacts to bats should be considered during project planning. This is especially important for bat species that are considered threatened or endangered under the Endangered Species Act (ESA). These bats include the Indiana bat (Myotis sodalis), which is found in the eastern part of the United States, including Illinois, Indiana, Iowa, Missouri, and Oklahoma; and the gray bat (Myotis grisescens), which is found in several states, including Missouri.

Currently in some parts of the country, no bat species are listed as threatened or endangered. However, that may change soon for states such as Nebraska, Kansas, Minnesota, and the Dakotas. On October 2, 2013, the U.S. Fish and Wildlife Service (USFWS) proposed the northern long-eared bat (Myotis septentrionalis) for listing as endangered under the ESA.

Map depicting the estimated range of the northern long-eared bat (from the Interim Conference and Planning Guidance: January 6, 2014)The northern long-eared bat species can be found in nearly the entire eastern half of the United States. While no determination has been made yet on the listing of the northern long-eared bat, the USFWS hopes to have a decision by October 2014. It is likely the species will be listed as endangered, especially with the recent spread of white-nose syndrome (WNS) across the eastern United States. WNS is a fungal disease that has terribly impacted many bat species. It has been especially disastrous for the northern long-eared bat. For example, in the northeast part of the species’ range, the population has declined by 99 percent.

Although these population declines have only been documented due to the spread of WNS, there is now concern that other sources of mortality or other stressors on the northern long-eared bat may drive the species to extinction. Thus, it is essential to consider the effect a project may have on this and potentially other bat species.

Projects that may impact the northern long-eared bat include those that involve:

  • Permanently or temporarily removing forested habitat that reduces the amount of bat habitat available for roosting, foraging, or travel. Bats may be directly disturbed or killed if such impacts take place while the northern long-eared bat is present.
  • Removing occupied, man-made roosting structures.
  • Using pesticides and herbicides in a way that exposes the northern long-eared bat.
  • Removing clean water sources, which could reduce drinking sources, foraging habitat, and/or prey availability.
  • Impacting water resources that flow into the northern long-eared bat hibernacula during the winter, which may affect the cave climate.
  • Clearing trees within five miles of caves or mines where hibernation occurs, which would reduce staging/swarming habitat for the bat.
  • Blasting and drilling within a half mile of caves or mines where the northern long-eared bats hibernate during the winter, as it may disturb hibernating bats.
  • Operating wind turbines, particularly during the fall migratory period.

Olsson staff members can help clients who have projects that may impact bats. Olsson has the equipment and experience needed to conduct bat acoustical monitoring, bat acoustical data analysis, and mist netting.

If you have additional questions on how the listing of the northern long-eared bat as an endangered species or any other environmental concerns may affect your project, please contact Joan Darling, PhD, at 402.474.6311 or jdarling@olssonassociates.com to learn how Olsson can help protect these important creatures.

Bat monitoring equipment set up in the field to conduct passive, acoustical bat monitoring.

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