If you look at a photo, it's pretty easy to tell a rat from a mouse: One's big; the other's little. But how do you tell which is which when all you have to go on are a few droppings or gnawed holes? That's where it gets a bit trickier because, in a lot of ways, rats and mice are very similar:

• Both are commensal rodents, which is just a scientific way of saying they don't mind being near people.



• Both find their way into homes, sheds, garages, and barns—in other words, wherever there are warmth and food.


• Both are known for chewing through walls, floors, clothing, furniture, wood, wires, and pretty much anything else.


• Both are potentially hazardous to humans, carrying a variety of diseases and triggering such conditions as asthma in some people.


• Both consume and contaminate food.



• Both leave behind droppings, tracks, and greasy smears from rubbing against surfaces like entry points, corners, and travel routes.


• Both are nocturnal, so they're most active at night.

Appearance 

Rat: A rat has coarse fur that can be red, brown, gray, or black, depending on the species, while their underbellies are usually lighter in color (think white or pale yellow). Adult rats tend to range in length from 11 to 19 inches, with an average weight of ½ pound to a pound. A rat's most notable feature is its long (6- to 9-inch), scaly, fur-less tail.

Mouse: A typical house mouse is small and black or gray with large ears, tiny black eyes, and a 3- to 4-inch long, hairless tail. Adults usually range from 6  to 7 inches long (including the tail) and weigh a mere ½ to 1 ounce.

Droppings

Rat: Rat droppings are capsule-shaped (like ibuprofen caplets) and about ¾ inch in length.

Mouse: Mouse droppings are rice-shaped—about ⅛ to ¼ inch long and narrow at one or both ends. Mice drop about 50 to 75 pellets per day. They're always scattered, never piled.

Markings

Rat: Rats will leave teeth marks on food, as well as large, gnawed, rough-edged holes about the size of a quarter. Also look for gnawing on pipes, water houses, wood beams, and electrical wiring.

Mouse: When a mouse gnaws, it leaves behind a small, clean-cut hole about the size of a dime. Look for gnaw marks on cardboard-like objects, as well as electrical wiring, soap, and plants.

Sounds & Activity

Rat: If you've got rats, you'll likely hear gnawing, scratching, and perhaps some fighting over food, especially during the quiet hours of the night. They're active climbers and swimmers, too, preferring elevated places like attics, roofs, walls, and fence tops.

Mouse:  Mice are scratchers and squeakers. If you have an infestation, you can expect to hear them in ceilings and walls. That's because they maintain contact with the drywall at all times so their whiskers and guard hairs can help guide them in the dark. They're also vertical climbers and jumpers and have excellent balancing abilities.

Breeding & Lifespan

Rat: Rats mate in spring and fall, with females delivering 4 to 6 litters a year, each with 6 to 12 babies. The average rat lives 1 to 2 years.

Mouse: A female mouse births up to 10 litters of 5 to 6 young every year. Mice reach reproductive maturity in 6 to 10 weeks, and live only about 1 year.

Nests

Rat: Some species of rats, like roof rats, prefer to nest up high in attics, trees, and dense vegetation, while others, like Norway rats, burrow and nest underground.

Mouse: Mice prefer to nest near heat sources like ovens, refrigerators, and water heaters. Their nests are usually made from shredded paper and fibrous materials.

• Remove food and water sources. Store your family's food, pet food, and birdseed in glass or metal containers with tightly fitted lids. Also, repair leaky faucets, don't leave water in the sink, and get rid of other open water sources.
• Eliminate possible shelter and nesting areas. Rats only need a ½-inch diameter opening to make entry into your home, garage, or outbuilding, and mice need even less space. Be sure to repair holes, fill gaps, and cover up openings with steel wool, hardware cloth, sheet metal, or even concrete.
• Apply rodent repellent spray around exterior entry points to keep mice and rats from looking for ways to get into your home. As an added layer of protection,  apply repellent granules around the perimeter of your home to prevent rodents from snooping around for food, water, and shelter in the first place.

How to Kill Mice and Rats

Both rats and mice multiply rapidly, so if you suspect they've already made their way into your home, you'll want to get rid of them as quickly as possible. The same approach can be taken for getting rid of either mice or rats.

• Place bait stations strategically. Put them along walls, in corners, and anywhere you see signs of rats or mice.
• For an easy-to-use, no-mess solution to eliminate rats, try the Tomcat® Rat & Mouse Killer Disposable Bait Station - Advanced Formula. It's pre-filled with bait which means there's nothing for you to do but place it and wait. Rats eat the bait and leave so you never have to see them again. When the bait is gone, just toss the empty station in the trash. Simple! For rat infestations, try the Tomcat® Rat & Mouse Killer Refillable Bait Station - Advanced Formula.
• To get rid of troublesome mice, try the Tomcat® Mouse Killer Disposable Bait Station - Advanced Formula. It's an extremely effective way to kill mice—a single bait block gets rid of up to a dozen mice*. Once the bait in the pre-filled station is gone, simply throw it away. For larger mice infestations, use the Tomcat® Mouse Killer Refillable Bait Station - Advanced Formula, instead.

For more information on using baits to get rid of mice and rats, read How to Use Bait Stations.

*1-oz bait block, based on no-choice laboratory testing.