The Difference Between Rats and Mice and Why It Matters

Mice Eat Everything and Rats Will Too Including Mice

A rat in a house
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Besides the fact that rats and mice look different, there are quite a few other differences between them. Your rodent control efforts will be most successful when you understand each of these pests fully. Knowing things like their behavior, food preferences, and habitats will help aid your control efforts. What works to control mice will not necessarily work to control rats.

The most common rodent pests in the U.S are the Norway rat, the roof rat, and the house mouse. Small mousetraps that work for mice will not work for much larger rats. And, rat traps set on the floor will not capture roof rats that tend to stay up high.

Difference between rats and mice
Illustration: Catherine Song. © The Spruce, 2018 

Mouse vs. Rat Behavior

One of the most important differences in behavior between mice and rats is that mice are curious and rats are cautious.

  • Cautious rats: Rats are very careful and will choose to avoid new things in their path until they have had time to get used to them being there. Because of this, you need to place unset traps in the rat's path before putting set rat traps there.
  • Curious mice: Mice are very curious and will investigate anything new. So you have to do just the opposite for them: set the trap and put it right in its path. In fact, if you do not catch a mouse in the first few days, the trap is probably in the wrong place and should be moved.

Physical Characteristics

There are over 70 species of mice and rats widely distributed across North America. The house mouse (Mus musculus), Norway rat (Rattus norvegicus) and roof rat (Rattus rattus) species are in the Muridae family, which is the largest family of rodents and mammals in the world.

  • House mouse: Small head, small feet, pointed snout, large ears with some hair. These mice have a light brown body with some gray shading and a dark tail. Adults weigh 0.5 ounces (15 grams). The mice droppings are shaped like rods.
  • Norway rat: Heavy and thick body, blunt snout, and short ears with dark hair. These rats have a brown body with black shading and a shaggy coat. Their tails are dark on top and pale underneath. Adults weigh 11 ounces (300 grams). Their droppings are shaped like capsules.
  • Roof rat: Light and slender body, pointed snout, large ears with no hair. These rats have a gray body with black shading and a smooth coat and a dark tail. Adults weigh 7 ounces (200 grams). Their droppings are shaped like spindles.

Mice Habitat and Breeding

Mice prefer to eat cereal grains and plants, but they will feed on almost anything. A mouse will build its nest in a hidden area near a food source. It will use just about any soft material or finely shredded paper to build its nest.

In one year, one female mouse can breed up to 10 litters of five to six babies. That is up to five dozen baby mice in one year. Now consider that those 60 offspring can begin to reproduce in as little as six weeks. Mice usually live about 9 to 12 months.

Mice Movement

Mice can stand up on their hind legs when supported by their tails. They do this to eat, fight, or figure out where they are. Mice are excellent jumpers, swimmers, and climbers. They can even climb up rough, vertical surfaces. They can jump 13 inches high and run along wires, cables, and ropes. Mice are fast runners. Moving on all four legs, they hold their tail up straight for balance. But if they are frightened, they will just run straight out.

Mice are nocturnal and most active from dusk until dawn. They do not like bright lights, but will sometimes come out during the day looking for food or if their nest is disturbed. A mouse can slip through 1/4-inch holes and gaps.

Mice Facts

  • The house mouse is considered one of the top 100 world's worst invaders.
  • Mice are afraid of rats because rats will kill and eat mice. Rat odor can be a strong deterrent to mice and affect their behavior.
  • Mice have a musky odor.
  • Mice are color blind, but their other senses, hearing, smell, taste, and touch are sharp.
  • Mice can be found indoors and outdoors including cities and rural areas.
  • Signs of mice presence include droppings, gnawing marks, and tracks.

Rat Habitats and Breeding

Rats will eat nearly anything, but they prefer fresh grain and meat. Rats need 1/2 to one ounce of fluid each day. If rats do not get this in the food they eat, they have to find water. Unlike mice, which rarely burrow, rats will dig under buildings, along fences, and under plants and debris. The Norway rat lives mostly in burrows while the roof rat nests in walls, attics, and trees.

Per year, a female Norway rat can have six litters of up to 12 young. These 70 rats can start to breed by the time they are 3 months old. Rats breed primarily in the spring. Rats can live up to 12 to 18 months. The roof rat has smaller litters of up to eight young and can have eight litters per year.

Rat Movement

Rats can enter a building through a hole as small as 1/2 inch in diameter. They are strong swimmers, so, rats will live in sewers and can enter buildings through broken drains or toilets. A rat will climb to get to food, water, or shelter. Rats follow regular routines and paths each day. If new objects are set in its path, it will do whatever it can to avoid it. Rats usually stay within 300 feet of their nest or burrow.

Rat Facts

  • Signs of a rat's presence are droppings, gnawing marks, tracks, runways, and burrows.
  • Like mice, rats are nocturnal, have very poor eyesight, but have very strong senses of smell, taste, and hearing.
  • Compared to mice, rats are much larger, have coarser fur, and have proportionately larger heads and feet.
  • The most common rat species in the U.S. are the Norway rat and the roof rat. These two do not get along and will fight each other to the death. The larger Norway rat usually wins.
  • Norway rats tend to live in lower floors of buildings and roof rats will live on the upper floors, so they can both infest the same building at one time.