Acoustic and Roost Box Preference Studies to Benefit Illinois Bats

by Teya Broyles | November 2, 2026 | Research

A close-up of a golden brown bat being held in the black gloved hand of a scientist.

A federally and state-listed northern long-eared bat from Birk 2 Mine. Photo by Joe Kath.

Throughout Illinois there are 13 bat species. Six of these species are Species of Greatest Conservation Need within the Illinois Wildlife Action Plan. Species of Greatest Conservation Need are species identified in the Illinois Wildlife Action Plan that are endangered, threatened, or have conservation status ranks indicating that they are at high or very high risk of extirpation in Illinois. All of these species are state listed in Illinois and three are federally listed.

A table with four columns and fourteen rows. Across the top, left to right, the title of the columns are bat species found in Illinois, species of greatest conservation need, Illinois Listed, and Federally Listed. The column with the bat species found in illinois include little brown bat, Indiana bat,southeastern myotis, gray bat, northern long-eared bat, eastern small-footed myotis, silver-haired bat, tri-colored bat, big brown bat, eastern red bat, hoary bat, evening bat, Rafineque's big-eared bat. The species of greatest need include Indiana bat, southeastern myots, gray bat, northern long-eared bat, eastern small-footed myotis, and Rafinesque's big-eared bat. The Illinois listed bats include Indiana bat, southeastern myotis, gray bat, northern long-eared bat, eastern small-footed myotis, and Rafinesque's big-eared bat. The federally listed bats include the Indiana bat, gray bat, and northern long-eared bat. — Bat species found in Illinois identified as Species of Greatest Conservation Need, State listed in Illinois and federally listed.

To improve conservation for bat species in the Midwest, a partnership between the Illinois Department of Natural Resources (IDNR), the Illinois Natural History Survey (INHS), the Iowa Department of Natural Resources, and Iowa State University was formed and continues work on Bat Conservation in Iowa and Illinois. The funding for this project came from the Competitive State Wildlife Grants Program through the U.S. Fish and Wildlife Service.

Acoustic Monitoring Project

Against the ceiling of a rocky cave are colonies of hibernating bats. They form brown irregular shapes on the ceiling. — Hibernating Indiana bats in southern Illinois. Photo by Tim Carter.

The first phase of this project (U-4-D-1) occurring from 2022-2024 and the current phase (U-6-D-1) will run from 2025-2027. This work continues and expands acoustic monitoring in both states and provides information to the North American Bat Monitoring (NABat) Program whose goal is to assemble data to deliver status and trends on North American bats. In addition, the results from this project inform IDNRs’ Endangered Species Program about the location of bats in Illinois.

One objective of this project is to expand the number of Long-Term Acoustic Monitoring Stations in Illinois. These stations provide co-located weather data and acoustic information outside of the standard NABat monitoring period (generally the summer active period) which allows for information to be gathered during migratory periods. Prior to the second phase of this project, there were four Long-term Acoustic stations in Illinois located at Jubilee College State Park, Warbler Ridge, Embarras River Bottoms and Magazine Mine. In 2026, new long-term acoustic stations were scheduled to be set up at Ayers Sand Prairie State Nature Preserve, Pere Marquette State Park and Morton Arboretum. The long-term acoustic monitoring station at Morton Arboretum was set up and has been active since June 18, 2026. The other two long-term acoustic stations are awaiting final approval of their installation locations.

Each of five pilot locations located in Iroquois County State Wildlife Area, Funks Grove, Dixon Springs State Park, Union County State Fish and Wildlife Area and Horseshoe Lake State Fish and Wildlife Area had temporary acoustic monitors installed in the spring of 2026 to inform site selection for future Long-Term Acoustic Monitoring Station Placement (Figure 3).

Effectiveness of Artificial Roosting Habitat Use

A map of the state of Illinois with the counties outlined and the rivers and lakes depicted in light blue. The legend of the map includes Long-term acoustic monitoring stations existing in their 1st installation marked by a blue circle, 2026 pilot marked by an orange circle, existing marked by a magenta circle. There are 1st installations at Ayers Sand Prairie, Morton Arboretum, and Pere Marquette. There are 2026 pilot stations existing at Iroquois County State Wildlife Area, Funks Grove, Dixon Springs, Union County Refuge, and Horseshoe Lake. There are existing stations at Jubilee, Warbler Ridge, Embarras River Bottoms, and Magazine Mine. — Figure 3: Long-Term Acoustic Monitoring Stations in Illinois Effectiveness of Artificial Roosting Habitat Use.

Another objective of this cooperative project is to examine the effectiveness of artificial roosting habitat use by bat species in Illinois. This project utilizes three different artificial roost types, including the chamber box, BrandenBarkTM and rocket box.

Chamber boxes are the classic “backyard bat house” with wooden sheets for the bats to roost between. BrandenBarkTM mimics loose bark on a dead tree. Rocket boxes are similar to the chamber box, but they wrap around a steel pole so bats can easily move around and select a preferred temperature within the box.

Three artificial habitat structures were installed at Forbes State Park in 2026, and the researchers will continue to identify suitable locations to place these bat boxes at Orient Bottoms State Fish & Wildlife Area and Pyramid State Recreation Area.

Species Use of Roosts

INHS researchers also conducted DNA analysis to determine which species were using the roosts. Twenty-one guano samples were collected and assessed from below roosts at Trail of Tears State Forest, Amboy Marsh, Sangamon River Forest Preserve, Lake of the Woods Forest Preserve and Siloam Springs State Park. The assessment was able to identify big brown bats (Eptesicus fuscus) and little brown bats (Myotis lucifugus) from these samples. Emergence counts were also conducted to determine how many individual bats were using these roosting sites. At two out of the five sites where emergence counts were completed, bats were seen emerging from the artificial roosting structures. This work helps us understand which species will use these roosts and determine the best management practices to conserve these species.

A photo collage of three images arranged side-by-side in a row. The photo on the left is a tall box designed for bat roosts on a tall metal pole. There is a gray overcast sky in the background. The middle photo is of a flatter box shape attached to a wooden telephone pole designed for bat roosts as well. In the background is a lush leafy woodland. The photo on the right is of a telephone pole wrapped at the end with fake tree bark also designed as a bat roost. In the background is a bright blue sky. — Figure 4: Bat roost styles from left to right: rocket box (Warbler Ridge Conservation Area), chamber box (Forest Glen Preserve) and BrandenBarkTM (Warbler Ridge Conservation Area).

Teya Broyles is a Graduate Public Service Intern at the Illinois Department of Natural Resources working in the Division of Natural Heritage. She is currently pursuing a master’s degree in Environmental Science with a concentration in Sustainable Development and Policy at the University of Illinois Springfield. She received her bachelor’s degree at the University of Illinois Springfield receiving a double major in Environmental Studies and Communication.