My earliest memories of bats are from watching Bela Lugosi in the old Dracula movies and the time a bat got into our farmhouse when I was maybe 11 years old.

I remember watching re-runs of Dracula movies on Saturday afternoons, wondering why a vampire and a bat were associated at all.  Of the 1,400 bat species worldwide, only three of them are true vampire bats, that is bats that “drink” blood.  Those three are in Central and South America, and they make a small wound on cattle and chickens and lap up the blood and are a mere 2-3 inches long, so they certainly are nothing we need to worry about here in Wisconsin.

My second memory is clear as day.  Waking up to the sound of my mom and dad yelling that there was a bat flying around the second story of our old farmhouse.  My dad was able to catch it with a sheet and release it outside, but I remember we were told to be careful outside in the evening because bats would get in our hair or the back of our shirts and come in the house.  As an adult, I’m not so sure that was accurate.  Why would a bat, flying around looking for insects to eat, look at an 11-year-old with a buzz-cut running around in the yard and think to itself ‘that looks like a good place to land and either rest or get insects?’  Still, that advice sticks with me 45 years later!

Actually, a third memory is when I was in India on a work trip.  We were outside a factory in a huge city, and in the very tall trees outside the building were gigantic fruit bats, known as Flying Foxes, sleeping for the day.  They are about 1 foot long, but their wingspan is about 4 feet, so when they open their wings, they are quite huge.   They are completely harmless to people and animals, as they eat fruit (hence their name) and drink nectar.  It is a bit intimidating to see large groups of these bats hanging in trees, stretching their wings out, but the locals were quite happy they were there.  Their eyesight is terrific, as they only eat fruit during the day, and the fruit isn’t running away like insects do!

Around here in southwest Wisconsin, we don’t have bats that big.  Our eight known species (of 1,400 bat species worldwide) are just a couple of inches long with 10-14 inch wing spans.  They are right around us almost every night, invisible to the eye and silent to the ear.  Since bats use ultrasound to detect insects and navigate in a process known as echolocation, electronic “bat detectors” are used to make their ultrasonic calls audible to our ears.  This is the technology the Department of Natural Resources (DNR) uses to monitor and study bats, and as a volunteer with the Friends of Vernon County Parks and Forests, I had the chance to do several bat surveys this year.  Each species of bat has a specific frequency range and waveform, so sonograms from the recordings can tell us what kinds of bats are around here.

As I walked over many different routes, including the City of Viroqua, four of our county parks, and some private properties, I felt a little bit like the folks in Ghost Hunters.  I’m carrying an ultrasonic detector with lights glowing, scanning the skies as I move, getting the occasional set of screeches telling me it’s detected a bat.  It’s dark, of course, because the routes start after sunset, but you can see surprisingly well even in near darkness.  Headlamps help for the occasional root or rock that’s in your way, and even with the white light on it’s not a disturbance to the bats.  Nature is also surprisingly noisy at night.  Bugs are flying around making noises, occasionally hitting you.  You can hear glugs from the water as fish and turtles move around and incredibly loud frog calls.  The occasional deer snorts and huffs in concern and thunders away into the woods.  As usual, every noise at night is amplified, so the little squirrel or mouse sounds like a bear or moose headed your way.

What aren’t visible or noisy at all are the bats.  I think this is one of the reasons that bats don’t get a lot of love, like birds or butterflies or bees.  They’re invisible and silent, so we don’t notice much if they’re around or if they’re not.  Birds, which I also enjoy, are fantastic to see and hear, and we revel in the miracle of migration every spring and fall.  It’s immediate satisfaction to see a flash of blue or yellow or red and to identify a bird.  Bats have great variety too, but in silence and invisibility, so it’s much harder to appreciate and enjoy.  In reality, though, we can’t hear them.  They’re really not silent, as the sonar call of the big brown bats are 138 decibels, like a siren or jet engine!  If we could hear bats in our audio range, we’d hold our ears all night!

On one evening, three of us walked a route around a county park listening for bats.  The younger- and sharper-eyed of us could see the bats until it got really dark, but I was going solely on the squawks and squeaks from our ultrasonic detector.  Later, I would learn from the DNR that we had heard five different species of bat on that one route.  Each bat species uses its echolocation at a specific frequency range and a specific waveform, so multiple species can be around you at the same time without conflicting with each other.  Their ears have dramatic shape differences to receive the signals unique to their species.  Some have ears that are small and pointy; others have ears that are huge and rounded-looking, almost like seashells cut in half.  They have grooves and shapes to optimize their ability to receive back the echolocating signal they are transmitting.  Even if multiple bats of the same species are around you, they will shift their ultrasonic signal just slightly from each other so they only hear their own signal return.  As an engineer, I am in awe of the functionality and efficiency of this system, enabling many bats at the same time to forage for insects in one area.  In pictures, they often look quite threatening, mouth open and teeth bared.  This is really because they are emitting their ultrasonic signals through their mouths trying to “see” what’s going on in front of them, not really because they’re mean or overly aggressive.

Bats are mammals, giving live birth and nursing their young.  The different species live from 10-30 years, and most give birth to one baby (in bat lingo a ‘pup’) each year.   Amazingly, bats breed in the fall, but delay fertilization until spring!  So female bats emerge from hibernation already pregnant.  We have Wisconsin bats that hibernate here, over the winter, in caves, but we also have bats that migrate south for the winter.  When you see a map of Wisconsin and where the over-wintering caves and mines are, 90% are in southwest Wisconsin – right here!  It gives me a sense of an extra obligation to do what we can to help bats since half of them spend their whole life here. The migratory bats go to the southern or south-central US, where they still hibernate, some in caves and some in tree hollows or crevices, since it is so much warmer there.

All of our bats are insectivores, with one bat eating as many as 3,000 flying insects a night during the summer.  In addition to eating nuisance insects like mosquitos (including those that carry West Nile virus), they are hugely important at eating insects that are agricultural pests.  They eat potato beetles, corn earworm moths, corn borers and cutworm moths, and coddling moths that impact walnuts.  The value of those pests being eaten by bats is estimated as $1B in Wisconsin alone!  Doing the bat surveys this summer here in Vernon County it’s easy to see why bats can be successful eating their body weight each night in insects.  The fireflies were so numerous on a couple of nights it was like flying into O’Hare Airport at night – lights blinking as far as you could see by the thousands.  When headlamps are turned on, the moths, beetles, fireflies, and other bugs are swarming overhead so thickly I think even I can catch them!

Insects aren’t totally without defenses, though.  Some insects emit ultrasonic signals to try to confuse the bats, what us Star Trek fans would call jamming signals.  Some of those insects can even be detected by the ultrasonic sensors we’re using to listen for bats.  Swallowtail butterflies have a little flap that hangs off the back of their wings, hence their name swallow-tail.  As Ed Yong shares in his book An Immense World, these tails produce echoes in the echolocation sonar of bats confusing them and causing them to sometimes miss the capture.  As I read this book, I realized that my imagination about these swallow-tails is limited by my five senses – was it there for some visual aid to mating, or to help it physically fly?  No, it was to help the butterfly to avoid bats’ echolocation, something I couldn’t even imagine!  As an aside, the book An Immense World is one of my absolutely must-read recommended books.  It is about the different ways animals and insects and plants sense the world around them and how it’s hard to even fathom sometimes how they do it, with only our five senses to go on.

In addition to pest control for agriculture, bats are pollinators for many crops.  Not so much here in Wisconsin, but on a global scale mango, banana, guava, and agave all require bats for pollination.  Agave is used for tequila, so thank you bats in Central America for my drink tonight!

A relatively new threat to bats is white-nose syndrome.  It was first identified in the US in 2006 in New York state and was discovered in Wisconsin in 2014.  Noted by a white powdery substance on the nose, the disease is caused by a fungus that disrupts the bat hibernation.  It causes the bats to wake up repeatedly in the middle of winter, when there isn’t insect life for them to eat, and they eventually die of starvation or other complications such as exposure to the elements.  When the fungus gets into a hibernation site, between 80-100% of the bats die in just a couple of years.  The fungus that causes white-nose syndrome is believed to have originated in Europe and is an invasive species here.  It’s believed European bats have some immunity, so they are not affected like our bats are.

So how are bats doing around here?  It’s hard to answer, partly because there isn’t a lot of data on how bats were doing before white-nose syndrome, or after.  That’s part of the reason I am doing bat surveys, so we can see how they are.  A DNR study at Yellowstone Lake State Park, just a little south of here, has shown population declines in roosts there from about 3,500 bats to 500 bats, an 85% decline over about three years, due to white-nose syndrome.  The good news is that those declines have stabilized, with populations the last six years remaining pretty flat, and maybe there’s actually been a slight increase in the last couple of years.  This could be because bats that survived that initial fatality have some kind of immunity, or the roosts they are using may be slightly less hospitable to the fungus, or something else.  The DNR is continuing to study the problem and trying out vaccines and other strategies to help the bats. It’s amazing that one fungus can cause so much destruction so quickly.  With our own recent history of COVID, imagine if we spent every winter packed into groups of tens to hundreds of thousands of people packed cheek to jowl to maintain our body heat, like the bats do.  It’s easy to see why such an infection could be devastating.

So, our bat populations are down as well, probably around 80-90% depending on the species.  The good news, though, is we’ve found five of the eight Wisconsin species in our surveys this spring, so they’ve at least survived.

One of the bats found in Wisconsin is on the Federal Endangered Species list – the northern long-eared bat.  The US Fish and Wildlife Service has proposed adding the tricolored bat (also known as the Eastern Pipistrelle) to the endangered species list and is currently reviewing the status of the little brown bat.  It’s clear that our bats are in trouble!  Vernon County is supporting its bats by joining the Lake States Forest Management Bat Habitat Conservation Plan.  This is an agreement between Wisconsin, Minnesota, and Michigan DNR departments and the US Fish and Wildlife Service to protect the bats but also to allow public and private landowners to use best practices to maintain their forests without prosecution for incidental destruction of bats.

Bats are sometimes seen during the day, and it’s generally not something to be alarmed about.  No matter what, you should leave wild animals alone, but sometimes bats are just going from one place to another, much as we might see someone driving around at night.  Less than 1% of bats carry rabies, but any animal that feels threatened may bit or scratch in defense, so leave them alone!  If you must interact with one, wear long sleeves and leather gloves, and verify that you haven’t been bitten or scratched.  If you are bitten by a bat (or any other wild animal), go to the doctor immediately.  The new rabies shots aren’t like when I was growing up, where we were terrified of getting 10 painful shots in the stomach (or at least that’s what they told us).  Now it’s just two shots in the arm; but it’s still not good to get rabies!

What can you do to help?

  • Just as with birds, promote insects in your yard. Plant native plants, and don’t use pesticides if you can help it.
  • Put up a bat roost. It’ll give them one more option for where to roost during the summer.  The bat houses we put up are NOT for winter hibernation but are for a place to roost and rest at night during the summer when they’re active.  Some roosts are also used as nursing roosts, where many female bats will join together to nurse their young pups.  Plans are available on the DNR website.
  • Don’t kill bats if they do get in your house. Open windows or doors to let them fly out on their own, or try to catch them and let them go outside.  For bats in the attic or other spaces, have your house sealed up by a professional who will let the bats out first then seal the holes up.
  • If you know of a cave or place where bats roost during the summer or overwinter, don’t go in! During the winter, when the bats are hibernating, going in and disturbing them can wake them up.  Waking up a bat causes it to burn the equivalent energy of 30 days of being in hibernation and can mean the difference between a bat waking up hungry or dying during the winter.
  • Do volunteer citizen science and work with the DNR to do bat surveys. There are opportunities to do roost counts (counting bats using a bat box) or doing walking or driving surveys using an ultrasonic detector, like the Friends group did in our county parks.  Adding data to the DNR database lets them make better decisions on how to positively impact bats.  I’d like to thank the other volunteers who helped train me and went out with me as I did the surveys around Vernon County – it’s a lot more fun and a lot safer with a partner or two!  Keep an eye on our Friends of Vernon County Parks and Forests Facebook page for results as we get them back from the DNR.
  • Donate to the Wisconsin Bat Conservation Fund:


Additional information on bats can be found here:

  • WIATRI (Wisconsin Aquatic and Terrestrial Resources Inventory)
  • Do Bats Drink Blood? By Barbara A Schmidt-French and Carol A Butler
  • An Immense World by Ed Yong
  • The Secret Lives of Bats by Merlin Tuttle
  • Wisconsin DNR, Wisconsin Bat Program
  • Bat Conservation International

Photo credit:  Liz Hamrick