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Like Most Bats, Evening Bats Live Up To Nocturnal Name

In October, bat decorations can be found anywhere you look, and they often look really similar to each other. But bats aren’t just fall visitors to Illinois; they live here for most of the year. And not all bats look the same. Right here in Will County we have eight different species of bats. They have their own distinct looks, habits, flight patterns and sounds. Today we’ll be getting up close and personal with one of them: the evening bat (Nycticeius humeralis).

(Photo via Shutterstock)

Now wait one minute. Aren’t all bats evening bats? After all, they are nocturnal. It is true that bats are nocturnal, which means they are most active in the evening. They sleep during the day and are awake at night. We can see them flying across the night sky once the sun starts to set and the sky begins to darken, and even later into the night if the moon is bright enough for us to see.

Even though most bats fit this description, this is the bat that got the evening bat name, and we don’t know why. Other bat species have different common names like little brown bats and hoary bats.

Take a closer look

Evening bats are on the medium side, which is still pretty small as far as bats go. Their bodies are about 3 inches to 4 inches long, and they only weigh a quarter ounce to a half ounce. That’s about as much as a pencil weighs. Evening bats have dark brown fur, but the hairs can be light gray at the tips. They have black ears, and their muzzles, or the part of the face with their nose and mouth, are wide, similar to dogs.

See the four “fingers” covered by patagia and the thumb on top. (Illustration via Shutterstock)

Bat wings are like human hands. They have four fingers that are covered by a hairless membrane called patagia. They have a clawed thumb on the top of each wing that is not covered. Their wings connect the legs, body and forelimbs, or arms. Evening bats’ wingspan is about 10 inches when flying, but they close their wings and tuck them in close to their bodies when they roost. Try this with your own hands: Spread your fingers wide like a bat’s flying wings. Then close them into tight fists like a bat roosting.

At home

Bats are often shown living in caves, but that’s not true for evening bats. Instead, evening bats live in forest habitats and open areas like wetlands and trees along riverbanks. They will roost, or rest and sleep, in the holes or cavities of trees and under loose bark. They will also roost in the attics of buildings.

(Photo via Shutterstock)

Evenings bats are not usually found in Illinois during the winter. Researchers think they migrate south to warmer weather, but more study is needed to be sure.

Growing up

Fall and winter are mating season for evening bats, but the females practice delayed fertilization and don’t become pregnant until spring. In May, female bats begin gathering together in maternity colonies that have anywhere from 15 to 300 bats. The adult males are not a part of these colonies. They live on their own, at least through summer and fall. Their winter habits are still a mystery.


Words to know

Membrane: A thin sheet of tissue acting as a boundary or lining.

Nocturnal: Active at night.

Roost: To settle or congregate for rest or sleep.


Most evening bats have twins, which is unusual for bats. Most bat species only have one baby, or pup, each year. The mothers roost together and help each other take care of the pups. Even within those large colonies of mothers and babies, a mother evening bat can recognize her own pup by its scent and sound. They are really caring moms!

Pups are fed by their mothers, or other mothers in the colony, for about three weeks. By then they can fly, turn and land and are practicing their hunting skills. Once they are 6 weeks old, the males are ready to survive on their own and leave the colony. The female pups will stay with the colony for a year. After a year they will leave to find a mate and become mothers themselves.

On the hunt

Have you ever heard the saying, "Blind as a bat?" Some people think bats have bad eyesight because they use echolocation to hunt in the dark, but that’s a misunderstanding. Bats have excellent eyesight, even in the dark. Echolocation is an adaptation, or special ability, bats have that helps them hunt with even more accuracy.

(Illustration via Shutterstock)

Bats make a chirping noise while they are flying to try to find prey to eat. Evening bats prey on insects. Those sound waves hit objects and bounce back to the bat. Using echolocation, bats can tell the location, size and shape of their prey, and even what direction it is flying!

Evening bats hunt for small flying insects like beetles, moths, spittlebugs and flying ants. They are slow and steady fliers. They fly high in the sky in the early evening before sunset and then fly lower later at night. While hunting for their food, evening bats are also trying to avoid being hunted themselves. Snakes, owls, raccoons and hawks would all be happy to catch a bat for their evening meal!

A friend to us

Among the insects evening bats like to eat are corn rootworms and spotted cucumber beetles. These two insects are considered major agricultural pests. That means they eat or damage crops that farmers are trying to grow. With their big appetites for insects, evening bats help control insect populations that may increase the amount of crops farmers are able to grow and sell. That’s good news for all of us, because we depend on crops to fill our own bellies. Thanks, evening bats!

To return the favor, we can be friends to evening bats by spreading the word about how they help us. We can also plant flowers that attract insects they like to eat and avoid using pesticides so what they eat is healthy and not poisoned with chemicals.


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