“What kind of frogs can you find in Illinois?”
I love finding, observing, and hearing frogs!
Even as a kid, I used to patrol the swamps by my house, catching them and then trying to sell them as pets to cars passing by. As you can imagine, no one was interested in buying my frogs, and I ended up letting them go at the end of each day. 🙂
Today, I’m providing a guide to teach you about the different kinds of frogs found in Illinois.
One of the BEST ways to find frogs is to learn the noises they make. So, in addition to pictures, you will find audio samples for each species below!
14 Frog Species in Illinois:
RELATED: 31 Common SNAKES That Live in Illinois! (ID Guide)
#1. American Bullfrog
- Lithobates catesbeianus
- Adult body lengths range from 3.6 to 6 inches.
- Coloration is typically olive green, with some individuals having gray or brown mottling or spots.
- Fully webbed back feet.
The American Bullfrog is the largest frog in Illinois!
Believe it or not, they can grow to weigh as much as 1.5 pounds (.7 kg).
American Bullfrog Range Map
Green = native range. Red = introduced range.
Bullfrogs can be found in permanent bodies of water, including swamps, ponds, and lakes. During the breeding season, the male frogs select egg sites in shallow waters, which they defend aggressively. A female will then select a male by entering his territory.
They are named for their deep call, which is thought to sound like a bull bellowing.
Bullfrogs are known to eat just about anything they can fit in their mouth and swallow! The list of prey includes other frogs, fish, turtles, small birds, bats, rodents, insects, crustaceans, and worms. I have personally witnessed one even trying to eat a baby duck!
#2. Northern Leopard Frog
- Lithobates pipiens
- Adults range from 2 to 4.5 inches long.
- Smooth skin is green, brown, or yellow-green with large dark spots.
- Lighter-colored raised ridges extend down the length of the back.
You can spot Northern Leopard Frogs in Illinois near slow-moving bodies of water with lots of vegetation. You might see them in or near ponds, lakes, streams, and marshes. I love how bright green most individuals appear!
Northern Leopard Frog Range Map
Due to their fairly large size, these frogs eat various foods, including worms, crickets, flies, and small frogs, snakes, and birds. In one study, a bat was even observed being eaten!
During the spring breeding season, the males will float in shallow pools emitting a low call thought to sound a bit like snoring. The Northern Leopard Frog may also make a high, loud, screaming call if captured or startled.
Northern Leopard Frog populations are declining in many areas, and the cause is not exactly known. It’s thought to be some combination of habitat loss, drought, introduced fish, environmental contaminants, and disease.
#3. Green Frog
- Lithobates clamitans
- Adult body lengths range from 2 to 4 inches, and the females are typically larger than males.
- Coloration is normally green or brown with darker mottling or spots on the back.
- Ridges run down the sides of the back and they have webbed hind feet.
Green Frogs are one of the easiest frogs to find in Illinois.
Green Frog Range Map
Look for them in permanent bodies of water, including lakes, ponds, swamps, and streams. They spend most of their time near the shoreline but jump into deeper water when approached. They also breed and lay eggs near the shore, typically in areas with aquatic vegetation.
The Green Frog produces a single note call that is relatively easy to identify. Listen for a noise that sounds like a plucked banjo string, which is often repeated.
To hunt, they use a “sit and wait” approach, so they are fairly opportunistic. Green Frogs will try to eat almost anything they can fit inside their mouth. The list includes spiders, insects, fish, crayfish, snails, slugs, small snakes, and even other frogs!
#4. Spring Peeper
- Pseudacris crucifer
- Adults are small and range from 1 to 1.5 inches long.
- They’re typically tan or brown, with the females being lighter in color.
- Both males and females usually feature a darker cross or ‘X’ on their back.
These tiny frogs can be found all over Illinois.
You’ll typically spot Spring Peepers on the forest floor among the leaves. However, they do have large toe pads that they use for climbing trees.
Spring Peeper Range Map
You can find them in ponds and small bodies of water in the spring, where they breed and lay eggs. After hatching, the young frogs remain in the tadpole stage for about three months before leaving the water.
Spring Peepers get their name from their distinctive spring chorus. They’re thought to sound a bit like baby chickens’ peeps, and they are most often heard in early spring! LISTEN BELOW!
Their calls are very distinctive, and once you know what to listen for, these frogs are very easy to identify by sound.
#5. Gray Treefrog
- Dryophytes versicolor
- Adult body lengths range from 1.5 to 2 inches.
- Mottled gray, green, and brown coloring. Look for a whitish spot beneath each eye.
- Bumpy skin, short snouts, and bright orange on the undersides of their legs.
Chameleons aren’t the only animal that can change colors! This incredible frog can slowly change colors to match what it’s sitting on to camouflage itself. They can vary from gray to green or brown. It’s common for their back to display a mottled coloring, much like lichen.
Gray Treefrogs are ubiquitous throughout Illinois. You’ll spot them in a wide variety of wooded habitats, from backyards to forests to swamps.
Gray Treefrog Range Map
They stick to the treetops until it’s time to breed. Gray Treefrogs prefer to mate and lay eggs in woodland ponds without fish. They’ll also use swamps and garden water features.
Gray Treefrogs are easier to hear than to see.
Listen for a high trill that lasts about 1 second, which is commonly heard in spring and summer.
*Gray Treefrogs are essentially identical to Cope’s Gray Treefrogs. The only way to tell the difference is to listen to their breeding calls. You can learn more by visiting this site.*
#6. Pickerel Frog
- Lithobates palustris
- Adult body length ranges from 2 to 4 inches.
- Dark green-brown coloration with two rows of dark squarish spots running down its back. Bright yellow color on the underside of hind legs.
- Females are typically darker and larger than males.
Pickerel Frogs prefer cool, clear waters in Illinois. You can find them in ponds, rivers, lakes, slow-moving streams, and even ditches.
Pickerel Frog Range Map
During the breeding season, the males attract females with a low, snore-like call. The females will attach egg masses to branches in cool water, where the tadpoles will spend 87-95 days before becoming frogs.
Pickerel Frogs are the ONLY poisonous frog native to Illinois.
When attacked, they produce toxic skin irritations that can be fatal to other animals and may cause skin irritation in humans if handled. As you can imagine, most predators leave them alone!
#7. Wood Frog
- Lithobates sylvaticus
- Adult body lengths range from 1.5 to 3.25 inches.
- Coloration is various shades of brown, gray, red, or green, with females tending to be more brightly colored.
- Distinct black marking across the eyes, which resembles a mask.
As the name suggests, Wood Frogs are found in Illinois in moist woodland habitats, including forested swamps, ravines, and bogs. They travel widely and visit seasonal pools to breed.
Wood Frog Range Map
This incredible little frog has a wide range across North America. They have adapted to cold climates by being able to freeze over the winter. Their breathing and heartbeat stop, and their bodies produce a type of antifreeze that prevents their cells from bursting. In the spring, they thaw and begin feeding again.
Interestingly, Wood Frogs seem to be able to recognize their family. Scientists have found that as tadpoles, siblings will seek each other out and group together!
Wood Frogs are one of the first amphibians to emerge after the snow melts.
Listen for a call that sounds a bit like a clucking chicken near vernal pools and other small bodies of water!
#8. Western Chorus Frog
- Pseudacris triseriata
- Adult body length up to 1.6 inches long.
- Smooth skin with color that varies from gray to green or brown.
- Dark brown or gray stripes that run down the back, dark stripe from the snout through the eye, and white stripe on the upper lip.
- Also called the Midland Chorus Frog.
In Illinois, look for the Western Chorus Frog in woodland ponds, marshes, swamps, meadows, and grassy pools.
Western Chorus Frog Range Map
For breeding, they try to find bodies of water without fish, including flooded fields, beaver ponds, roadside ditches, marshes, and shallow lakes and ponds. The female attaches small masses of eggs to underwater vegetation.
Western Chorus Frogs are secretive and nocturnal, so they can be hard to spot. Your best way to locate one is to use your ears.
Listen for a unique call that is rapid and relatively short and sounds a bit like running your finger over the teeth of a comb.
#9. Southern Leopard Frog
- Lithobates sphenocephalus
- Adult body lengths range from 2 to 3.5 inches.
- Coloration is brownish to green with large darker green or brown spots on its back, sides, and legs.
- Lighter ridges extend down the sides of the back, and the upper jaw sometimes has a light, yellow stripe.
The Southern Leopard Frog will occupy various freshwater habitats in Illinois. They are more terrestrial than many other true frogs and are often seen far from water. It’s also common to spot these frogs out on rainy nights!
Southern Leopard Frog Range Map
They breed during the winter and spring, particularly during periods of heavy rainfall. These frogs often nest communally, and the females attach egg masses to aquatic vegetation.
Make sure to listen for their low, chuckling croak! Some people describe the sound like a “squeaky balloon” or a “ratchet-like trill.”
For food, Southern Leopard Frogs primarily eat invertebrates, such as insects and crayfish.
#10. American Green Treefrog
- Dryophytes cinereus
- Adults can grow up to 2.5 inches long and have smooth skin.
- Yellowish-green to lime green with pale yellow or white undersides.
- White stripes down their sides sometimes have black borders.
Green Treefrogs can be hard to find in southern Illinois since they spend most of their lives high in trees. They also can change color based on light and temperature.
American Green Treefrog Range Map
During mating season, they visit ponds, lakes, marshes, and streams to breed and lay eggs. They prefer bodies of water with a lot of vegetation.
Their breeding call is a repeated, abrupt, nasal “bark.“ Sound is typically the best way to locate these treefrogs.
Green Treefrogs are often kept as pets. They are popular because of their attractive appearance, size, and how easy it is to take care of them. For example, they don’t require artificial heating like most amphibians. But being nocturnal, it’s unlikely you will see them moving around much, so they are probably not the most exciting pets!
#11. Crawfish Frog
- Lithobates areolatus
- Adult body lengths range from 2.2 to 3 inches.
- Yellow to tan or brown with dark brown or golden circles over their body.
- White undersides.
Look for Crawfish Frogs in Illinois in grassland and prairie habitats, including meadows and pastures.
Crawfish Frog Range Map
They get their name from their habit of living in crayfish burrows for most of the year. These frogs rarely stray far from the burrow as they offer protection from predators and weather, including winter frost and prairie fires.
During the spring, the frogs breed during mild, rainy weather. The males seek out seasonal pools and wetlands free from fish, such as flooded pastures, roadside ditches, and ponds.
Males attract females with a low, loud, snore-like call.
The Crawfish Frog is now listed as “near threatened” on the ICUN Red List. Their main threats include habitat loss, disease (chytridiomycosis), and competition with other frogs.
#12. Plains Leopard Frog
- Lithobates blairi
- Adults are 2 to 3.75 inches long.
- Tan or light brown coloration with dark brown or greenish spots.
- A distinct white line on the upper jaw and lighter ridges running down the sides of the back.
As the name suggests, this frog is found on the plains of Illinois.
Plains Leopard Frog Range Map
The Plains Leopard Frog is almost always seen around permanent bodies of water, including streams, creeks, ponds, and marshy areas. They primarily eat insects, although these opportunists will eat almost any living thing they can fit in their mouth (including other frogs).
During the breeding season, the males produce a guttural, rapid “chuck-chuck-chuck” call.
The Plains Leopard Frog is relatively common but can be hard to see. First, they are nocturnal. Second, they are shy and dive into the water as soon as they are approached!
#13. Blanchard’s Cricket Frog
- Acris blanchardi
- Adults range from 0.6 to 1.5 inches long.
- Warty skin is typically tan, brown, olive green, or gray with darker banding on the legs.
- Dark triangular mark between the eyes on the head.
Blanchard’s Cricket Frogs can be found in or near permanent bodies of water in Illinois, including bogs, lakes, ponds, marshes, and slow-moving rivers and streams. They can also sometimes be spotted in temporary bodies of water such as flooded fields and drainage ditches as long as there is a permanent water source nearby.
Blanchard’s Cricket Frog Range Map
Interestingly, although they are in the “treefrog” family, they spend most of their time on the ground and in the water.
Unfortunately, Blanchard’s Cricket Frogs are declining in parts of their range and are considered threatened. They face habitat loss, chemical contamination, and competition for resources. Another pressure they face is their short life span, as the average individual only lives one year.
Males make unique, repetitive, metallic breeding calls.
The calls are thought to sound like two pebbles or marbles being clicked together. The females lay small clusters or even single eggs, and the tadpoles emerge in late summer.
#14. Bird-voiced Treefrog
- Dryophytes avivoca
- Small treefrog that grows up to 2 inches long.
- Normally pale grey or brown, but it can also be shades of pale green.
- Look for a dark cross-shape on their back and darker limbs.
Bird-voiced Treefrogs are found in the southern tip of Illinois in swampy forests, marshes, and wetlands. They look very similar to the larger Gray Treefrog, so be careful when identifying.
Bird-voiced Treefrog Range Map
These nocturnal frogs rarely leave the trees, except on rainy nights to breed. Females deposit their eggs into shallow pools and then leave to head back upwards. Tadpoles take about a month to metamorphize into adults, who then disperse into the forest.
Another way to correctly identify this species is to listen for them. Their “wit-wit-wit” sound is distinctive. While it’s mainly heard at night, don’t be surprised to hear a few males calling during daylight hours.
As you can probably guess from their name, many people think they sound like a bird!
Do you need additional help identifying frogs?
Try this field guide!
Which of these frogs have you seen in Illinois?
Leave a comment below!