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Wild About Illinois Bats!

Thirteen species of bats are currently recognized as living in Illinois. They are small mammals, and all of the bats of Illinois feed on insects. Because insects are not available year-round in Illinois, bats must hibernate, migrate or adjust their activity in some manner to survive the winter. Bats are the only mammals with true flight. Their wings are made of the skin of the arm, hand and fingers. Mating occurs in late summer or fall with fertilization delayed until late winter or spring. Female bats bear live young and feed them after birth with milk produced from the mammary glands until they are able to hunt on their own. Predators of bats include cats, raccoons, hawks, owls, shrikes, opossums, skunks, snakes and weasels. Six of the 13 bat species in the state are listed as endangered or threatened. Cave closures, habitat loss and/or disturbance (for roosting and feeding), accumulation of insecticides, intentional killing, wind turbines and diseases, such as white-nose syndrome, are all contributing factors to the reduction of bat populations. Human fears and misunderstandings also negatively impact bats.​

External Structures

Species Gallery

Kingdom: Animalia - Animals are multicellular organisms that rely on other organisms for nourishment. There cells do not have cell walls. Most animals are capable of movement at least in some portion of their life cycle. Reproduction is generally sexual, but in some animals asexual reproduction may be utilized at certain times.
Phylum: Chordata - The Phylum Chordata contains the vertebrate animals. Mammals, birds, reptiles, amphibians and fishes are included in this phylum. These animals have a notochord at some point in their development. They have a tubular nerve cord along the back. Gill slits and a tail are present at some point in their life cycle. They have an internal skeleton.
Class: Mammalia (Mammals) - Mammals are warm-blooded. Most mammals have young born after developing inside the mother's body in a special organ called a uterus. After birth, the young are fed with milk produced in the female’s mammary glands. A mammal has a large and complex brain.
Order: Chiroptera (Bats) - Bats are the only true-flying mammals. Their hands are modified into wings. They use echolocation to find food, but small eyes are present, and they can see well. The tragus at the base of the ear assists in hearing.
Family Vespertilionidae: (Evening Bats and Vesper Bats) - A prominent tragus (a piece of skin that extends into the middle of the ear) is present in all of these bats. There is no leaflike flap on the nose. They eat insects. Some bats that live in Illinois in the summer migrate out of the state in the winter, while other bats hibernate. Illinois’ female bats undergo delayed fertilization. They mate in fall and store sperm in their uterus until ovulation occurs after the female exits hibernation.
     eastern red bat (Lasiurus borealis)
     hoary bat (Aeorestes cinereus)
     Rafinesque's big-eared bat (Corynorhinus rafinesquii) [state endangered]
     silver-haired bat (Lasionycteris noctivagans)
     big brown bat (Eptesicus fuscus)
     tri-colored bat (Perimyotis subflavus)
     evening bat (Nycticeius humeralis)
     gray bat (Myotis grisescens) [state and federally endangered]
     southeastern bat (Myotis austroriparius) [state endangered]
     northern long-eared bat (Myotis septentrionalis) [state and federally threatened]
     eastern small-footed bat (Myotis leibii) [state threatened]
     little brown bat (Myotis lucifugus)
     Indiana bat (Myotis sodalis) [state and federally endangered]


All bats that live in Illinois have a special hearing system for locating food and navigating in the dark. The process is called echolocation. In echolocation, bats send out high-pitched squeaks that bounce off objects and return to the bat as echoes. Humans usually cannot hear these sounds although we can hear some other sounds that bats make. 

Bats' large, sensitive ears help to collect the returning sound waves. The tragus is a pointed projection of the external ear. It helps channel sound waves into the ear. Echolocation allows bats to recognize the size, shape and texture of an object and determine if it is moving. It is only used on objects that are a short distance away from a bat. With this system, bats may fly accurately in total darkness.


Bats are very important ecologically and economically. They are predators of night-flying insects. They reduce insect pests of agricultural crops. They disperse plant seeds. Although none of the species that live in Illinois do so, many bat species are pollinators.

Bat populations are declining worldwide. In Illinois, four of the 13 species present in the state are listed as endangered and two are threatened. Cave closures, habitat loss and/or disturbance (for roosting and feeding), accumulation of insecticides, intentional killing, wind turbines and diseases,

What can be done to help bat populations in Illinois? The Illinois Wildlife Code, the Illinois Endangered Species Protection Act and the federal Endangered Species Act are laws that help protect bats. The Illinois Cave Protection Act is designed to protect caves and the animals that live in them. Gates that allow bats to enter and exit but keep people out have been installed at the entrance of some caves. Forest habitat and large, dead trees can be preserved. Bat houses can be built or purchased and installed. Education is a tool being used to overcome negative perceptions of bats.

White-nose Syndrome

little brown bat showing signs of white-nose syndrome
Photo © U.S. Fish and Wildlife Service

White-nose syndrome is a disease that is devastating bat populations in North America. Caused by the fungus Pseudogymnoascus destructans, it has resulted in the death of millions of bats. This fungus grows in cold, moist conditions, and hibernating bats are very susceptible. It was first found in the United States in the winter of 2005-2006 in New York and spread quickly. White-nose syndrome was first detected in Illinois in the winter of 2012-2013.

The fungus is present in Europe, but it does not cause such high mortality rates there. It is believed that it reached the United States by someone unintentionally transporting the fungus from Europe. Clothes, equipment and shoes can transport the fungus. Bats can carry and pass along the fungus through physical contact with other bats. The fungus appears as a white coating on the nose and wings of infected bats.

Infected bats change their behavior. They may fly outside in winter. They hibernate closer to a cave entrance than normal, where temperatures are colder and not as stable as deeper in the cave. Infected bats become active more often than normal, using up fat reserves needed for hibernation. Infected bats usually die of freezing or starvation. The Indiana bat, eastern small-footed bat, tri-colored bat, little brown bat, northern long-eared bat and big brown bat are the species most affected. All of them hibernate in caves. Currently, there is no method to treat infected bats or eliminate the fungus. Some caves have been closed to people, but bat-to-bat contact and physical transport cannot be stopped.

Bats and Rabies

All mammals are susceptible to rabies, and some mammals act as a reservoir for these viruses (Family Rhabdoviridae, genus Lyssavirus). The rabies virus attacks the central nervous system, resulting in swelling of the brain and sometimes the spinal cord. Rabies infections generally occur when saliva from the infected animal enters a wound on the victim's skin, such as from biting or scratching with claws. A rabies infection can be fatal to any mammal, including humans. The wild mammals in the United States most commonly affected by rabies are foxes, raccoons, skunks and insect-eating bats.

In Illinois, most rabid animals found are insect-eating bats. Humans are more likely to be in contact with rabid bats than other rabid animals because bats tend to live in closer association with humans. Rabid bats are often slow-moving or sluggish and may be seen during the day in places that you would not expect to see a bat.

The main method of avoiding bat-related rabies infection is to not pick up or touch bats. Your pets may contact a rabid animal without your knowledge. Dogs in Illinois must be vaccinated for rabies. Many local governments also require cats to receive rabies vaccinations. These efforts greatly reduce the spread of rabies to humans.

If you see a bat that you think might be showing symptoms of rabies infection, call your local animal control department, police department or natural resources biologist to report it. Do not pick up or touch the animal.

The incidence of rabies in wild bat populations is very low. Rabies rates in bats tested for this disease tend to be higher because many more bats that are diseased or injured are tested than are healthy bats. In the United States, very few people are infected with rabies each year. A vaccine to combat the virus is effective if administered soon after exposure. If you should be bitten by an animal suspected of having rabies, seek medical assistance immediately.

Click here for the IDNR pamphlets Bats and Rabies and Bats and You.

Educational Resources & Bibliography

Feldhamer, George A., Hofmann, Joyce A., Carter, Timothy C., and Joseph A. Kath. 2015. Bats of Illinois. Indiana State University Center for Bat Research, Outreach and Conservation, Terre Haute, Indiana. 84 pp.

Hofmann, Joyce E. 2008. Field manual of Illinois mammals. Illinois Natural History Survey, Champaign.
358 pp.

Illinois Department of Natural Resources. 2001. Bats and Rabies.

Illinois Department of Natural Resources. 2020. Checklist of Illinois endangered and threatened animals and plants.

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