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Most of the bats being found outside are large brown bats, the most common kind of non-migrating cave bats native to Wisconsin.
The recent streak of unseasonably warm weather pleases many humans but it’s causing problems for the already-stressed Wisconsin bat population.
Spring-like temperatures are bringing hundreds of common large brown bats out of hibernation but once awake, the flying mammals are not yet finding an ample supply of bugs to eat. This can leave bats too weak to move or otherwise return to their roosts until food supplies improve, wildlife experts say.
The normal high temperature this time of year ranges from 26 to 38 degrees Fahrenheit, according to the National Weather Service, but Madison reached 62 degrees on March 8.
As a result, bats in various stages of distress are turning up in yards, parks and driveways in the Madison area. Some are attached to outside walls; others are tucked into corners of windows seeking shelter.
“Whenever we get these big temperature fluctuations, bats start showing up and we’re seeing a lot of them right now,” says Paige Pederson, a licensed wildlife rehabilitation specialist with the Dane County Humane Society.
The Dane County Humane Society, a nonprofit which serves a 12-county region in southwest Wisconsin, has been fielding calls from the public and accepting bats brought into the center. About 90 percent of the animals are large brown bats, the most common of the four kinds of non-migrating cave bats native to the state.
Pederson says bats who have been hibernating in attics or basements can get fooled when the weather warms suddenly.
Once outdoors, bats who can’t find adequate food quickly lose strength.
“Any bat you find outside this time of year is going to need some sort of intervention to keep it alive,” she says.
Bat populations in Wisconsin are already under pressure from white nose syndrome, a devastating fungal disease first discovered in New York in 2006 that has since spread east and into Canada. It’s considered the biggest threat ever to North American bat populations, leading to 100 percent declines in some species.
White nose syndrome has already had a major impact on all four of Wisconsin’s cave bat species: big brown bat, little brown bat, northern long-eared bat and eastern pipistrelle.
Bats are a key part of the ecosystem; they disperse seeds and consume many types of pests and insects. They are considered vital in reducing risks of mosquito-borne diseases such as West Nile virus.
If you find a dormant bat be careful not to handle or otherwise injure it, says Lisa Juday, a Dane County animal control officer.
Juday suggests trying to scoop the bat into a plastic container with a lid using a small piece of cardboard.
“People should exercise a modicum of caution but bats don’t pose any threat to people,” she says.
Dane County will respond to bat calls but taking the animal directly to the Humane Society is probably the best way to ensure its survival. Call 608-287-3235 for more information.
Rehabilitation specialist Pederson says the good news for bats is that more people are starting to realize their important role in the natural environment and the need to protect them. She says the best thing someone can do is put a bat house on their property.
“I’m glad to see more people are realizing how great bats are,” she says. “They need our help.”
