DNR research reveals bats’ nighttime secrets

Courtesy of the Wisconsin Department of Natural Resources

WISCONSIN – As Wisconsin’s cave bats return to their winter hibernation sites, Wisconsin Department of Natural Resources (DNR) bat biologists are analyzing new information to help solve the mystery of where these nocturnal creatures spend their nights in summer.

The research aims to help the DNR better understand bats’ summertime behaviors and movements, and how their populations are rebounding from white-nose syndrome. This deadly disease of bats has decimated Wisconsin’s cave bat species since it was first detected in 2014.

Tracking bats movements’ year-round

For several years now, DNR bat biologists and partners have been installing technology in major bat winter hibernation sites to automatically record when bats arrive and when they leave. The remote technology gives the DNR a variety of important information without having to send bat biologists to faraway sites to look for bats outfitted with numbered metal bands placed on bats in previous years.

The DNR started to expand the remote technology to bats’ summer roosts starting in 2020. Biologists captured and inserted microchips in 81 bats at Yellowstone Lake State Park and Governor Dodge State Park in southern Wisconsin before releasing them. The microchip is the size of a grain of rice and is automatically read when the bat flies past an antenna system. Antennas to read the microchips were placed in a total of five bat houses at the same state parks in spring 2021.

“In the wake of white-nose syndrome we have very little information on survival of bats at summer roost sites,” said DNR Bat Biologist Heather Kaarakka. “We’re starting to get a picture of survivors at winter sites, but what’s happening at summer sites is still largely a mystery.”

By tagging bats, the DNR is learning about returning bats that are surviving white-nose syndrome, how they move around in summer and their behavior.

The research can help the DNR make more informed decisions about suitable roost box design and construction, how many boxes bats may need, and when to manage bat houses or build roosts based on bat phenology.

First arrivals at bat houses

While the bat biologists are still analyzing data, early results are solving some bat mysteries.

Tagged bats started to return to the bat houses at Yellowstone Lake State Park and Governor Dodge State Park in early April. Overall, 27 tagged bats were recorded at Yellowstone Lake State Park and 17 at Governor Dodge State Park.

Bats moved often among the 20+ bat houses at Yellowstone Lake and one bat tagged at Yellowstone Lake even made a stop at Governor Dodge in spring during her migration back to Yellowstone Lake.

“It’s pretty exciting to be able to track these bats this way,” said J. Paul White, DNR bat team lead. “It’s redefining our idea of a roost and how these bats are using it. “Before this we had a sense that a particular bat or colony would mostly use one bat house. If you look at data from this summer, however, it’s rarely the case that a bat is using a roost box for a sequential stretch of time, like a week or two. They are using different roosts periodically and likely roosting in other nearby bat houses or attics every so often.”

The research will continue in 2022 as part of a larger project coordinated by the United States Geological Survey (USGS) National Wildlife Health Center to develop a vaccine against white-nose syndrome.

For more information on Wisconsin’s bat population, visit www.wiatri.net/inventory/bats/.

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