State research sheds light on bat supermoms and summer habitats

MADISON – State conservation biologists radio-tracking cave bats to learn more about their summer habitats are also turning up insights into the strength, stamina and sacrifices of mother bats.

DNR Conservation Biologist Heather Kaarakka radio-tracks a bat to help learn more about the habitat it needs during the summer.
DNR Conservation Biologist Heather Kaarakka radio-tracks a bat to help learn more about the habitat it needs during the summer.
Photo Credit: Michael Kienitz

The Wisconsin research is part of a multi-state, multi-year project with Minnesota and Michigan that is funded by a federal grant to learn more about several hibernating bat species that use forests extensively in summer and whose populations have been decimated by white-nose syndrome in eastern states in recent years. The information will help continue to allow forest management that will ultimately benefit the bats.

“Unfortunately, we’re unlikely to find something to stop the disease in Wisconsin. So we are trying to gather information that will allow us to do the best job in managing bats in the post white-nose syndrome landscape,” says Heather Kaarakka, a DNR conservation biologist and one of the researchers.

White-nose syndrome is a deadly disease of bats that does not affect humans but covers bats in a fungus that awakens them while they are hibernating, burning precious energy stores and leading to starvation. White-nose syndrome was first detected in Wisconsin in 2014 and has spread across the state; sites where the disease was first documented have seen some bat populations decline by more than 90 percent.

Bats play an important role in Wisconsin’s ecosystems and economy; they are voracious insect eaters, with a 2011 North American study estimating that bats save Wisconsin’s agriculture industry between $658 million to $1.5 billion annually in pesticide costs.

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Radio-tracking cave bats

To conduct their research, Kaarakka and DNR biologists Paul White, Katie Luukkonen and Jennifer Redell set up fine mesh nets in the bats’ travel corridors. When a bat of interest, either a northern long-eared bat or an eastern pipistrelle, flies into the net, they quickly retrieve it and if it’s a female of a species of interest, they attach a small radio transmitter between the shoulder blades using nontoxic, temporary glue.

The researchers return on subsequent days and nights to find the bat and track it back to the tree where it roosts; to count bats emerging from the roost, and to assess and catalog information about the habitat including the tree species, height of the roost, proximity to water and more.

Their research has revealed that northern long-eared bats are incredibly adaptable to the environment they are in, White says. They use a lot of different tree species, both live trees and dead trees, and are found in the crevices or under bark that is sloughing off the trees. “We do think they can positively respond to sustainable forestry,” he says.

Radio-tracking of eastern pipistrelles started in 2016 and will continue next year to further understand their habitat needs. First-year results revealed the bats roosting in leaf clusters in trees in small groups of six to 14 bats.

Eastern pipistrelles may forage as far as 2 miles away from their roost and are switching roosts much more than expected. The mothers may be moving their pups every day and a half, perhaps to stay ahead of predators. The pups grab onto the mother and move, no small feat for a flying mammal that weighs only 7 to 9 grams, White says.

“Male bats have a pretty easy life. They mate and feed themselves. The females leave the hibernation site early, give birth to one or more pups, nurse the pups and feed themselves,” he says. “All of that makes it very challenging for a female bat to survive.”

Across their field work, the researchers captured more male eastern pipistrelles in their nets than females. White worries that this imbalance may be a sign that white-nose syndrome has killed females and fewer of them are out on the landscape this summer.

All of the data DNR researchers collect will be provided to a contractor that will be getting data as well from Minnesota and Michigan researchers and using the information to develop a bat habitat conservation plan for the Upper Midwest. Due to declines caused by white-nose syndrome and continued spread of the disease, the northern long-eared bat was listed as threatened under the federal Endangered Species Act on April 2, 2015.

DNR research continues in 2017 to learn more about the eastern pipistrelles’ summer habitats. People can help fund this and other bat research to better help Wisconsin bats recover from white-nose syndrome by making a tax deductible donation to the Natural Heritage Conservation Program — choose “Mammals – Bats” from the drop-down menu for the donation fund.

To learn more about Wisconsin bats and sign up to receive updates about bat news in Wisconsin  search the DNR website,, for saving Wisconsin bats or visit the Wisconsin Bat Program website.