Important Facts about Mice and Rats

Two brown rats
Ben Queenborough/Photodisc/Getty Images

Both rats and mice are common pests of households (and businesses!). Rats may be associated with squalor and poverty but the truth is that they can flourish as well in a penthouse as they can in an outhouse. Some scientists speculate that mice evolved from rats to fit situations that did not require ferocity or large size, but instead offered shelter by entering through small holes. 

Because of this possible evolution, rats and mice do have a number of commonalities. However, they also have a great number of differences. They may seem as though they look a lot alike (especially if one is scurrying across your floor!), but if you are able to look closely, you will see distinct differences between rats and mice—as well as between different species of each. Because of these physical differences, as well as behavioral variations, the pest control methods that will be successful are different for rats and mice as well.


9 Key Differences Between Rats and Mice

Thus, successful control of any pest is dependent on the ability to correctly identify the specific pest. Just knowing that it is a rodent is not enough. For example, if you set out small, wooden mouse traps when you actually have rats, the traps will be ineffective. And if you set rats traps along the floor, but really have roof rats (that tend to stay up high—thus their name), the traps will collect little more than dust.

This article discusses the physical differences between common rats and mice, particularly focused on adults. At the end of the article are links to articles on control of these common rodents. Once you know what the pest is that has invaded your home or property, you can begin to take steps to control that rodent pest.

Following are the most notable physical attributes of the most common rat and mouse pest in the U.S.: the Norway rat, the roof rat, and the house mouse—along with a couple of facts on reproduction and nesting of these rodents, and pictures of common rats and mice. (Note: the following are attributes of the adult rodents.)

Mice vs rats illustration
Illustration: © The Spruce, 2018 

Body Shape

  • Norway Rat: Heavy and Thick body, weigh 11 ounces or 300 grams
  • Roof Rat: Light and Slender Body, weigh 7 ounces or 200 grams
  • House Mouse: Small Head, Small Feet, weigh 0.5 ounces or 15 grams

Snout Shape

  • Norway Rat: Blunt
  • Roof Rat: Pointed
  • House Mouse: Pointed

Ear Size and Hair

  • Norway Rat: Short, Dark Hairs
  • Roof Rat: Large, No Hair
  • House Mouse: Large, Some Hair

Tail Coloration

  • Norway Rat: Dark Above, Pale Underneath
  • Roof Rat: All Dark
  • House Mouse: All Dark

Fur Color and Characteristics

  • Norway Rat: Brown with Black Shading, Shaggy Coat
  • Roof Rat; Grey with Black Shading, Smooth Coat
  • House Mouse: Light Brown with Grey Shading

The Shape of Feces or Droppings

  • Norway Rat: Capsule-Shaped
  • Roof Rat: Spindle-Shaped
  • House Mouse: Rod-Shaped

Daily Food Requirements

  • Norway Rat: 1 ounce or 28 grams
  • Roof Rat: 1 ounce or 28 grams
  • House Mouse: 0.1 ounce or 3 grams

Litter Size and Frequency

  • Norway Rat: 8-12, 7 Litters per Year
  • Roof Rat: 6-8, 8 Litters per Year
  • House Mouse: 6-7, 8-10 Litters per Year

Nest Locations

  • Norway Rat: Burrows, mostly
  • Roof Rat: Walls, Attics, Trees
  • House Mouse: Stored material

Now that you know all about the physical characteristics of common rodents, you need to know how to get rid of rats or mice in your home! Following are some important articles that provide this information: