The Bats of Chicago

October 29, 2013

For the last couple years, Lincoln Park Zoo’s Urban Wildlife Institute has spent some time listening to the skies. Because of this data, we now have a pretty good idea of who is flying around at night, chomping up all of the nighttime insects, from moths to mosquitoes.

Now that the weather is turning cooler, most of our bat friends have travelled to their wintering grounds, be them local caves or warmer spots down south. But with Halloween around the corner, it’s time we became better acquainted with our nighttime neighbors. And while these animals might seem particularly spooky this time of year, don’t let their haunting reputation fool you: bats are an essential part of our ecosystem, even in cities!

Of the eight species flying around Chicago, here are five of the usual suspects we see and hear at night.

Creative Commons picture of a hibernating big brown bat. Photo by Ann Froschauer/USFWS.

Big Brown Bats

They’re one of the most common city-dwellers. Females of this species can live in groups of 60 or more individuals. They raise their pups together in these maternity colonies and come back to the same group year after year.

Bats are very long lived for their size, often reaching 15 years of age. Because of this, some research suggests that big brown bats might have “friends” within their colonies, and these friendships can last for years! Unfortunately, big brown bat populations have suffered in recent years due to white-nose syndrome.

An eastern red bat in Indiana. Photo by John Farabaugh.

Eastern Red Bat

The most brightly colored of our local bat community, this species has beautiful red fur. They spend their winters in the southern United States and have been known to hibernate on the forest floor among the fallen leaves. Like most bats, this species has one or two pups every year.

Creative Commons picture of a hoary bat. Photo by jumpingspider.

Hoary Bat

The biggest member of our bat community, but it weighs only 35 grams, the equivalent of about 35 pennies! They have a wingspan of about 1.5 feet. This bat is named for the grayish-white sheen of its fur. They live solitarily in the treetops during the summer and are generally not known to be found in cities. Despite this, we regularly hear them flying around the zoo at night.

Creative Commons picture of a silver-haired bat, cropped and retouched. Photo by LassenNPS.

Silver-haired Bat

Another bat named for its appearance, silver-haired bats are medium sized and appear almost black with very subtle silver-tipped fur. As a tree-roosting bat, silver-haired bats are solitary, roosting alone in tree cavities, beneath bark or among leaves. We have detected silver-haired bats throughout the Chicago area, including downtown.

Creative Commons picture of a tri-colored bat. Photo by David J. Thomas.

Tri-colored Bat

This is our smallest member of the Chicago bat community, weighing only 8 grams (or 8 pennies!). This species is found across eastern North America and has been tragically affected by white-nose syndrome. Some populations have suffered declines of up to 95 percent. This species spends winter in caves and mines near their summer grounds, where they hibernate until the temperatures warm up in spring.

Julia Kilgour

Julia Kilgour, M.S., is an adjunct scientist with Lincoln Park Zoo’s Urban Wildlife Institute. She’s looking for your help to find large bat colonies in the area to study! Send your bat photos, stories, and tips to

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