Bat Appreciation Month—GAI Performs Studies on Federally Listed Bats

More than a dozen species of bats live in the Northeastern and Midwestern United States (U.S.), making their homes in caves, trees, rocky outcrops, and even attics and barns.

October is Bat Appreciation Month. In recognition, GAI Consultants (GAI) is highlighting two federally listed bat species—the Indiana Bat (Myotis sodalis) and the Northern Long-eared Bat (Myotis septentrionalis). The federally endangered Indiana Bat lives in the eastern half of the U.S., while the federally threatened Northern Long-eared Bat resides in the Eastern and North Central U.S. and all Canadian provinces. Each year, female bats of these species gather in the forest in groups called “colonies” to give birth and raise their young. They feed exclusively on insects and can eat hundreds per night—essentially offering farmers and local residents a form of natural pest control.

Federally Listed Bats

Since their populations have dwindled, these bat species have been placed on the list of federally protected species under the Endangered Species Act. The Indiana Bat and Northern Long-eared Bat now face the threat of White-Nose Syndrome, a new fungal disease that affects bats during winter hibernation and has reduced their numbers by more than 90 percent in some states.

Tree Clearing—Surveying for Federally Listed Bats

Although they hibernate in caves in the winter, the Indiana Bat and Northern Long-eared Bat spend the summer months roosting under loose bark or inside tree cavities, so they are particularly sensitive to any disturbance to forested habitat. Our clients’ projects oftentimes require tree clearing; therefore, to protect federally listed bats that might be using trees for habitat, GAI’s bat biologists are deployed to conduct surveys and determine if listed bats are present. In the event that the listed bats live within the project area, extra measures must be taken to ensure the species are protected.

Mist Net Surveying—Humane and Safe Inventory of Bats

GAI’s bat biologists are recognized as qualified bat surveyors by the U.S. Fish and Wildlife Service and individual state agencies across the Eastern and Midwestern U.S. One method they use to survey for federally listed bats is called mist netting. Mist nets are placed across forested corridors such as roads, trails, or streams, where bats travel between roosting and foraging areas. These corridors, or “tunnels” through the forest, can vary from 10 to 60 feet wide. The mist nets are made of thin polyester mesh and are strung on pulley ropes between anchored poles that can reach almost 30 feet high. When properly placed, mist nets are nearly undetectable to unsuspecting bats as they travel through these areas.

Conducted over multiple nights per area, these bat surveys start at dusk and continue for upwards of five hours nightly. Surveys can only be performed during good weather to ensure that conditions are ideal for catching bats. GAI’s bat biologists diligently monitor mist nets to remove captured bats quickly and identify and record data on each bat before its release. Bat biologists rely on their experience to ensure the bats are handled safely and humanely throughout the survey. They use flashlights to find their way in the dark, but conduct mist net surveys quietly and without damage to survey areas.

For questions or additional information about federally listed bats and/or bat surveying, contact GAI’s in-house bat biologists Adam Mann at 859.692.4122 or Jason Duffey at 859.692.4152. To learn more about Bat Appreciation Month and how to get involved, visit

For related information, check out the following articles and blog posts:

Bat Box Installation: An Effective Mitigation Strategy | March 31, 2016
Northern Long-Eared Bat – Section 4(d) Rule Finalized 2.16.16 | February 11, 2016
A Peek into the Nightlife of a Bat Biologist | August 6, 2015
Northern Long-Eared Bat Gets Federal Protection | May 4, 2015
The Indiana Bat | August 29, 2012

Learn More.