Utility Links


Archive - August 2019

What are Bats?
Bats are mammals. Like all mammals, they have four limbs. They have hair (fur). Their body temperature is kept at the same level regardless of the outside temperature except when they are hibernating. Their young are born after developing inside the mother's body in a special organ called the uterus. After birth, the young are fed with milk produced in the female’s mammary glands. Bats have a complex brain. Bats are the only mammals with true flight. Their wings are made of the skin of the arm, hand and fingers.
How Big are They?
The hoary bat (Lasiurus cinereus) is the largest bat species in the state with a wingspan of 13.4-16.1 inches. The smallest bat species of Illinois are the tri-colored bat (Perimyotis subflavus) and the eastern small-footed bat (Myotis leibii) each with a wingspan of 8.0-10.0 inches.
Where Do They Live?
Bats can be found statewide. However, each species has its own preferred habitats. Some bat species are restricted to specific regions of the state. See the list of species at the end of this page for more details.   

How Do They Reproduce? 
Mating occurs in late summer or fall with fertilization delayed until late winter or spring. Female bats bear live young (pups) and feed them after birth with milk produced from mammary glands until the pups can fly on their own. 

What Do They Eat?
All bats of Illinois feed on insects. Some catch insects in flight. Some glean insects that they find while crawling on vegetation. Others use a combination of both techniques. Because insects are not available year-round in our state, bats must hibernate, migrate or adjust their activity in some manner to survive the winter. 

Does Anything Eat Them?
Predators of bats include cats (Felis catus), raccoons (Procyon lotor), hawks, owls, shrikes, opossums (Didelphis virginiana), skunks (Mephitis mephitis), snakes and weasels. 

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, such as white-nose syndrome, are all contributing factors to the reduction of bat populations. Human fears and misunderstandings also negatively impact bats. 

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
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. 

Thirteen species of bats are currently recognized as living in Illinois. More information about each species and bats in general can be found on the Illinois Bats poster from the IDNR. Order or view the poster on the publications page. This poster was funded in part by the Decatur Audubon Society, Decatur, Illinois. 

eastern red bat (Lasiurus borealis)
Wingspan: 11.0-13.0 inches  
Illinois Range and Habitat: statewide; associated with trees 
Status: common from spring through fall 

hoary bat (Lasiurus cinereus)
Wingspan: 13.4-16.1 inches    
Illinois Range and Habitat: statewide; associated with trees
Status: common during spring and fall migration and present in summer 

Rafinesque's big-eared bat (Corynorhinus rafinesquii)
Wingspan: 10.0-12.0 inches  
Illinois Range and Habitat: a few counties in southern Illinois; swamps and forests along streams
Status: endangered in Illinois 

silver-haired bat (Lasionycteris noctivagans)
Wingspan: 10.0-12.0 inches  
Illinois Range and Habitat: statewide during migration; associated with forests 
Status: common during migration

big brown bat (Eptesicus fuscus)
Wingspan: 12.0-14.0 inches 
Illinois Range and Habitat: statewide year-round; variety of habitats 
Status: common

tri-colored bat (eastern pipistrelle) (Perimyotis subflavus)
Wingspan: 8.0-10.0 inches 
Illinois Range and Habitat: statewide; forests and agricultural areas
Status: common

evening bat (Nycticeius humeralis)
Wingspan: 10.0-11.0 inches     
Illinois Range and Habitat: statewide in summer; agricultural fields and woodlands   
Status: common in summer

gray bat (Myotis grisescens)
Wingspan: 11.0-12.0 inches 
Illinois Range and Habitat: counties along the central and lower Mississippi River, the Ohio River border counties and LaSalle County; associated with forests and caves
Status: endangered in Illinois and federally

southeastern bat (Myotis austroriparius)
Wingspan: 9.5-10.5 inches   
Illinois Range and Habitat: southernmost eight counties; associated with swamps, forests and streams  
Status: endangered in Illinois

northern long-eared bat (Myotis septentrionalis)
Wingspan: 9.0-10.5 inches  
Illinois Range and Habitat: statewide; associated with large, contiguous tracts of forests
Status: threatened in Illinois and federally

eastern small-footed bat (Myotis leibii)
Wingspan: 8.0-10.0 inches 
Illinois Range and Habitat: two counties in extreme southern Illinois; upland habitat with exposed rocks and caves 
Status: threatened in Illinois

little brown bat (Myotis lucifugus)
Wingspan: 8.7-10.6 inches 
Illinois Range and Habitat: statewide; associated with farm fields, forest edges and urban areas 
Status: common

Indiana bat (Myotis sodalis)    
Wingspan: 9.0-11.0 inches
Illinois Range and Habitat: present in southern and central Illinois in summer and in southern Illinois in winter; associated with mines, caves, forests, swamps and streams 
Status: endangered in Illinois and federally