Did you find a mouse or a rat in Illinois?
First, I hope it was outside and NOT in your house. 🙂
Second, I’m guessing you’re here to try and identify the correct species. Luckily, you’ve come to the right place! I’ve compiled a list of the most common mice and rats that live in Illinois, with photos and range maps to help find the one you’re looking at.
Unfortunately, mice and rats can be hard to identify. First, many species look similar to each other. In addition, due to their shy nature and small size, it can be hard to get a good look. You may want to consider purchasing the book below if you need additional help with rodent identification.
Here are 8 COMMON Mice and Rats Found in Illinois!
#1. Brown Rat
- Rattus norvegicus
The Brown Rat is among the most widespread rats in Illinois!
It goes by many names, including the common rat, street rat, and sewer rat. You may also know it as the gray rat or Norway rat.
Interestingly, the Brown Rat isn’t native to North America. Instead, it’s thought to have originated in China and Mongolia.
Look for Brown Rats anywhere people are living, particularly in urban environments. They’re best known for living in sewer tunnels and subway systems, scavenging food from the trash.
Although many people find rats off-putting, others keep a sub-species of Brown Rats as pets. This subspecies, called the Fancy Rat, was bred specifically for the pet trade. Besides companion animals, rats can be trained for many jobs to assist humans, like detecting gunpowder for forensic teams and providing therapy support.
It’s a misconception that Brown Rats spread bubonic plague. In actuality, it’s more commonly spread through ground squirrels! Regardless, Unfortunately, they can still transmit infections of many kinds though as their blood can carry several diseases,
#2. Black Rat
- Rattus rattus
The Black Rat is a naturalized species in North America. It’s thought to be native to India but was transported here on cargo ships and has become so widespread that it’s no longer considered a foreign species.
It’s considered a pest in the agricultural market because it feeds on a wide variety of crops. Like other rodents, Black Rats can carry pathogens in their bodies. While they may not appear sick, they can spread infections like toxoplasmosis, typhus, and bubonic plague.
In many areas where the Black Rat was once the dominant species, the Brown Rat has taken over. Black Rats are slightly smaller and reproduce less often, which are two of the reasons this species isn’t as widespread as Brown Rats.
Black Rats go by many common names, such as ship rat, roof rat, and house rat.
#3. Eastern Meadow Vole (Field Mouse)
- Microtus pennsylvanicus
You probably know this species as a Field Mouse or Meadow Mouse, but it’s a vole, which is a similar type of animal. The Eastern Meadow Vole uses burrows for nesting, shelter, and rest. They create woven grass nests placed in the burrows or under logs.
As their name suggests, they prefer grassland or open forest habitats. Like most mice in Illinois, the Field Mouse is a dietary generalist, which means they will eat many different types of food. Garden plants, flowers, crops, and grasses are common food sources.
Field Mice are an important food source for many predators, including birds of prey, snakes, and wild and domesticated cats.
Although they’re very easily recognized and a well-known species, the Field Mouse is not commonly found in homes. It prefers open space and grasses to eat, so it will ignore a populated area in favor of its preferred habitat.
#4. House Mouse
- Mus musculus
Most mice in Illinois can live around people, but few thrive as well as the House Mouse!
If you picture a small, mischievous cartoon mouse when you think of mice, then you’re probably familiar with this species! House Mice have the characteristic large ears, thin tails, and tiny bodies of a typical “mouse.” They do incredibly well in highly populated areas, and there are now more semi-tame populations than wild. These populations live near people and depend on them for food and shelter.
House mice are the most common species to find inside your home because they’re so adaptable to human presence. They readily eat food scraps, build their nests in walls or dark attics and basements, and spend most of their time hidden from view. In fact, you’ve likely shared your home with a House Mouse at least once over the years. Although most people would prefer not to have them, they aren’t the worst roommates!
Like their eating habits, they are adaptable in their social behavior. Populations of House Mice that have an excess of food, like those that live in buildings, form a hierarchy with leaders and followers. However, in the wild, where food is less plentiful, females aggressively protect their territory from one another.
#5. Golden Mouse
- Ochrotomys nuttalli
Unlike other mice in Illinois, Golden Mice are picky eaters and almost exclusively eat seeds.
The Golden Mouse is named for its soft fur, ranging in color from a golden brown to burnt orange. Look for them in thick woodlands and swamps where they hide in vegetation. They’re especially fond of red cedar and honeysuckle plants.
Their tails are prehensile, which means they’re used as an extra appendage for balance, standing on two legs, and aid in climbing or running.
#6. Eastern Deer Mouse
- Peromyscus maniculatus
Eastern Deer Mice are one of the most widespread mice in Illinois.
Its various subspecies are spread all over the country. To identify, look for a small gray or brown mouse with large black eyes, round ears, and white feet.
They can reproduce throughout the year, although they typically only do so in the warmer parts of their range.
Although we generally think of mice as ground creatures, Eastern Deer Mice prefer to nest high up in hollow trees. Their sharp claws allow them to climb to incredible heights!
In addition to spending time in forests, this species is also commonly found in houses! They feed on food scraps and crumbs and make nests in small spaces. Because they’re so numerous and widespread, they’re incredibly hard to get rid of if you have an infestation.
#7. White-footed Deer Mouse
- Peromyscus leucopus
Like other mice in Illinois, this species is a vector, which means it carries and spreads disease.
Many rodents can carry disease-causing pathogens without getting sick, making them ideal carriers for these germs. For example, hantavirus, which causes severe disease in humans, and the bacteria that cause Lyme disease are transmitted by this mouse.
Although many people keep White-Footed Deer Mice as pets, there are probably more people that live with this species unwillingly! That’s because this is one of the most likely species to find in your attic, garage, or basement. Even though they can spread disease, contamination isn’t very common in homes.
This is the species I’ve found in my house, and I use a live trap and release them in a field a few miles away. Here’s the one I use!
#8. Western Harvest Mouse
- Reithrodontomys megalotis
This nocturnal species is most active on particularly dark nights. Your best chance to see one would be during the new moon after dusk.
Unlike other mice in Illinois, the Western Harvest Mouse is a strict herbivore and does not typically consume insects. Instead, it feeds primarily on fruit, grasses, and seeds.
Western Harvest Mice will occasionally eat grasshoppers and caterpillars if these food sources become scarce. They nest on the ground and spend most of their time there, only rarely venturing into shrubs or low trees in search of food.
Do you want to learn about other MAMMALS in Illinois? Check out this field guide!
- 20 COMMON Mammals in Illinois! (ID Guide)
Which of these mice and rats have you seen before in Illinois?
Tell us below in the COMMENTS section!