Mice and rats are related, but some key differences will help you identify your invader
Mice are small enough to squeeze into holes the size of a pencil.
Rats are larger and heavier than mice with coarse, scaly tails.
Mice eat mostly plants and grains, while rats eat almost anything.
Rats are cautious and difficult to trap, so professional extermination is recommended.
If you notice crumbs strewn about your pantry or hear scratching in your walls, rodents are likely afoot. Mice and rats are common pests with enough similarities that it can be tough to tell them apart. In either case, you'll want to eliminate the infestation to prevent the spread of diseases carried by rats and mice. We break down their distinct looks and habits to help you strategize.
The clearest difference between mice and rats is their size, but there are many other ways to identify and differentiate between the two.
| Type of Difference | Mice | Rats |
|---|---|---|
| Size | 5–7 in (incl tail) | 16–18 in (incl tail) |
| Weight | Up to 1 ounce | Up to 1 pound |
| Color | Light gray or brown | Gray, brown, or black |
| Feeding | Plants and grains | Eats anything |
| Damage | Gnaw marks on cords | Musky odor near food |
| Disease | Can carry disease | Can carry disease |
| Eradication | DIY trapping | Professional pest control |
| Prevention | Seal small gaps | Keep home clean |
Mice and rats are similar in appearance, being small rodents with round ears and long tails. They're so similar, in fact, that juvenile rats can be tough to distinguish from full-grown mice. As adults, however, the two are easy to tell apart.
The most obvious difference between mice and rats is their full-grown size. Mice only grow to be two to four inches long with a three-inch tail, weighing up to an ounce. Rats are significantly larger at seven to nine inches long with a tail of equal length and a weight of up to one pound.
Although both critters come in neutral shades of white, brown, or gray, rats tend to have much darker fur, while mice have lighter hues. Rats can even be dark brown or black. As an added indicator, rats are often dirty enough to leave grease marks on surfaces they touch.
While more subtle, you may be able to spot a difference in body shape if you get a good look at your home invader.
| Mouse | Rat |
|---|---|
| Thin, fur-covered tail | Thick, coarse, and hairless tail |
| Large, round ears | Small ears relative to its size |
| Pointed nose with long whiskers | Round, blunt snout |
Even if you don't see the pest itself, you may see its droppings. Mice poop often, leaving small, dark, pointy droppings about the size of a grain of rice everywhere they go. Rat droppings are larger, with a rounder shape, about the size of a raisin.
Aside from their looks, you can tell mice and rats apart by how they behave. Mice tend to be bolder than rats, exploring new things (including baited traps). Rats are far more cautious and usually won't go for bait, which makes them tougher to trap.
Mice and rats are scavengers, but mice tend to be pickier eaters. They prefer to eat plants, grains, and certain processed foods. Cereals are a favorite of mice, including cereal-based dry pet food. Mice also make more of a mess when eating, leaving crumbs scattered around their feeding areas.
Rats, on the other hand, will eat just about anything. They'll also clean up after themselves, so you may not see evidence.
Mice and rats are both found all over the world in nearly every climate. They are both nocturnal, active mostly at night.
You'll find mice nesting near their food sources, often in kitchen cabinets. Because they can climb, they may also make their home inside wall cavities or attics.
Where rats live depends on the type of rat. Brown Norway rats live in low places like crawl spaces and basements because they don’t climb well. They may also burrow under buildings and gardens. These strong swimmers can even enter a home through sewers and plumbing pipes. Black roof rats are strong climbers, however, and may enter through attics and eaves.
Mice and rats produce similar damage in a home while nesting and feeding. Look for the following subtle differences to tell them apart.
Both critters like to gnaw on things around your home, chewing through walls and wires to reach food and create nesting material. Rat teeth marks are about an eighth of an inch long. Mice marks are smaller.
Mice and rats urinate often to mark their territory. However, mice will sit and eat their food where they find it. If you notice a strong, musky scent around food sources, that’s one of the common signs of mice.
Lifecycle is one area where mice and rats are largely the same. Both reproduce rapidly, producing 25 to 60 pups per year throughout several litters. Once born, wild mice and rats with adequate shelter live for one or two years. As such, a small family of either animal can quickly become an infestation in your home.
Both mice and rats are known carriers of dangerous diseases, bacteria, and viruses. These include leptospirosis, Hantavirus Pulmonary Syndrome, LCMV, rat-bite fever, and salmonellosis.
For this reason, it's often best to let a local mice and rodent exterminator handle your infestation. Coming into contact with contaminated food, droppings, or animals (dead or alive) may pose a risk to you and others in your home. Pros will have the sanitary knowledge to remove an infestation safely.
Prevention techniques are similar for mice and rats, ranging from basic property maintenance to reinforcement of your perimeter. Some homeowners also use essential oils as a rodent deterrent.
The best strategy to rodent-proof your home is exclusion. Mice can squeeze into holes the size of a pencil, while rats can enter any opening larger than a half-inch. To seal a house from mice, plug weak spots in its perimeter with screens, flashing, door sweeps, and heavy-duty sealants so pests can't get through.
Even more important are indoor and outdoor sanitation. Mice and rats are attracted to potential food and water sources. Clean up garbage, food debris, and clutter so they have nothing to eat and nowhere to hide.
When you're strategizing on how to get rid of mice, start with the prevention techniques above. Then, set up mice traps with the right bait—try peanut butter or seeds. Mice won’t eat most other protein-based food sources.
If your home already has a rat infestation, large traps baited with protein are one potential strategy. However, rats are very cautious creatures that don't always go for bait, so DIY pest control can be difficult. Calling a professional pest exterminator near you is the most efficient and effective option.
No, mice do not become rats. While their similarities may make them appear to be the same animal at first, they are distinct in their appearance, behaviors, and the strategies used to remove them. Juvenile rats that have not reached their full adult size may be roughly the same size as mice, making them hard to tell apart.
It may be better to have a mouse in your house than a rat. Rats are larger, more aggressive, and more difficult to eradicate once settled. One rat can cause more damage than one mouse. However, both animals pose a danger in that they can spread bacteria and contaminate food, so you’ll want to contact an exterminator as soon as you detect an infestation of either animal.
