Bat Week is October 24-31.
CHAMPAIGN, Ill., 10/26/20: Thirty minutes before sunset, Illinois Natural History Survey (INHS) scientists and volunteers set up chairs in the prairie grass at Coles County’s Warbler Ridge Nature Preserve, look up at the summer twilight sky, and wait for the bat show to begin. Soon, the bats emerge from their bat houses to feed and fly off into the night.
A good showing of bats is exciting news for the scientists: bat-focused habitat conservation efforts have proven to be effective in attracting and nurturing bat populations, but this work can take time to pay off.
The INHS Illinois Bat Conservation Program (IBCP) partnered with Grand Prairie Friends (GPF), an Urbana-based, non-profit conservation organization, in 2018. In the first two years of the project, Grand Prairie Friends purchased additional acreage, planted trees and pollinating plants, added wetlands, and erected 12 artificial roosts in two locations within Warbler Ridge.
In 2018 the IBCP team collected acoustic bat calls and captured bats using mist netting to determine relative bat activity and which species were residing in Warbler Ridge. In 2019 and 2020, the scientists and GPF volunteers returned regularly to observe the newly erected structures at sunset to determine if bats were emerging from structures. Increasing bat populations indicated that the restoration efforts were successful.
“Bats have many interesting habitat requirements, such as water sources, trees for roosting, and foraging areas,” said INHS biologist Mark Davis. “This effort was a holistic, ground-up restoration where they tried to provide everything a bat population might need to thrive in central Illinois.”
The INHS project’s goals were to collect baseline bat data in 2018, site the artificial roosts based on collected data, and observe population changes over time as the restoration project advanced. The new roosts provided a location from which to observe the bats and serve as habitat until newly planted trees are old enough for roosting.
Scientists selected two kinds of bat structures unlike the typical bat house, including the tall, double-chambered rocket box and BrandenbarkTM, an artificial bark. The bats’ most popular structure so far is the artificial tree bark placed atop 20-foot telephone poles at the forest’s edge and close to a creek, according to mammologist and program coordinator Tara Hohoff.
The bat house design allowed bats to move in and out of the direct sun so they could regulate their own temperatures. Some bat species roost in dead trees under the bark, so the bat structures simulated these conditions.
Bats will seek out new roosts only if they need them, such as when a dead tree falls or loses its bark or forests stands are cleared. Hohoff said she hoped that bats would choose the bat houses but didn’t anticipate they would move into their new homes so soon.
“I kept saying to volunteers, ‘don’t get too excited; it may take a while,’” she said. In 2019, there were not any bats using the structures, but they filled the sky during the surveys in 2020. In one structure, they found more than 100 bats.
“We got lucky that the bats needed a new roost and they found ours,” Hohoff said. “Our success in drawing the bats was probably a combination of bat house placement, giving bats the option of different types of houses, and their need for a new roosting location.”
As Hohoff observed bats exiting the structure in 2020, she used an ultrasonic recorder to try to identify what species they were. The most common bat she recorded was the evening bat. During mist netting in 2018, they confirmed presence of big brown, eastern red and evening bats. The acoustic data from 2018 suggests there are also tri-colored, little brown, and hoary bats at the site.
In the past few decades, bat populations have dwindled in the state.
“Bats are having a tough go of things in Illinois because they have the deck stacked against them,” Davis said.
Some species are strongly affected by white nose syndrome, a deadly fungal disease. Wind turbines kill thousands of bats each year, and agricultural pesticides kill insects that bats eat. Loss of natural habitats to cropland or development also limits bat populations.
The conservation project is an example of how restoring habitats is a boon for bats.
“It becomes clear when we see what used to be a cornfield now harboring a population of bats that restoration works,” Davis said.
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Media contacts: Mark Davis, 217-300-0980, davis63@illinois.edu; Tara Hohoff, 217-300-6554, thohoff2@illinois.edu; news@prairie.illinois.edu