What Is The Difference Between a Rat, a Mouse, and a Rodent?

Rats, mice– what’s the difference? Aren’t they just the same little varmint scurrying around the house? 

To the untrained eye, rats and mice might not look all that different, but there are a number of key characteristics that set them apart from each other. We’re talking about some physical distinctions as well as differences in patterns of behavior.

Why do we need to know the difference between rats, mice, and other rodents? Mostly it’s to help with your pest control efforts– what might work for rats won’t necessarily work for mice, or perhaps even for other rodents, for that matter.

What Are Rodents?

There used to be a time when any small, wild mammal seen scurrying around your farm, garden, or home was referred to as a “varmint”. 

Not all varmint are rodents, however. (Though it can be argued that all rodents are varmint critters!)

Rodents belong to a classification of mammals (of the order Rodentia) characterized by a pair of incisors in each of their upper and lower jaws. These front teeth are growing constantly, hence the need to just as constantly gnaw on something to somehow whittle these down to a more functional length.

An estimated 40% of all mammalian species are rodents, which should give you an idea just how numerous they are. 

Rats and Mice Are Both Rodents

Both mice and rats are rodents. There are dozens of different species of both rats and mice, but in the United States, the most common rodent pests are:

  • the Norway rat
  • the roof rat
  • and the house mouse

As far as physical characteristics go, here’s a quick way to tell the difference: 

  • The house mouse is quite small– about half an ounce. The head is comparably smaller than the rest of its body with a pointed snout. Ears are proportionately larger. Coloration is typically light brown with a touch of gray. Droppings are shaped like small rods.
  • The Norway rat looks thick and bulky, weighing about 11 ounces. Bodies are brownish with shades of black. The snout is comparatively blunter, and the ears are short. Tails are commonly dark on top and pale underneath. Droppings are capsule-shaped.
  • Larger than the house mouse but not quite as big as the Norway rat, at around seven ounces, the roof rat looks like the link or transition between the two. It has the characteristic pointed snout and large ears of the house mouse, with the general coloration and darker tail of the Norway rat. Droppings are shaped like spindles.

Some more important distinctions between the rats and mice are:

  1. Behavior: rats are generally a lot more cautious, while mice are a lot more curious. 
  2. Feeding: both mice and rats will eat anything, although mice prefer cereals, grains, and plants. Rats, on the other hand, will also have a preference for meat (including mice if really pressed for food!).
  3. Nesting: mice will prefer to have a nest hidden away but close to a food source. Norway Rats will choose to live in burrows, while the roof rat will prefer nesting in walls, attics, or trees.
  4. Territory: mice are generally afraid of rats, so you won’t commonly find mice in the same home as rats. You can have both Norway rats and roof rats however, with Norway rats hanging around the lower floors of the building while roof rats stay towards the upper floors. These two rat species don’t get along, however, so they give each other a wide berth.

More Common Rodents (Other Than Rats and Mice)

Of the varmints and critters you are likely to find in North America, here is a short list of other mammals that fall in the classification of rodents:

  • Beavers
  • Capybaras
  • Chinchillas
  • Chipmunks
  • Flying squirrels
  • Gerbil
  • roundhogs
  • Guinea pigs
  • Hamsters
  • Lemmings
  • Marmots
  • Porcupines
  • Prarie dogs
  • Squirrels
  • Voles

Animals Commonly Mistaken as Rodents (But Aren’t)

To further make the distinction, here are some animals that are usually lumped together in the same category as mice and rats, but are not actually rodents— and are, instead, of a different category of small mammalian creatures:

  • Bats. They might look like winged mice, but they’re of a totally different order, known as Chiroptera.
  • Hedgehogs. Also not rodents, and in fact, are more closely related to shrews rather than, say, porcupines.
  • Moles, which belong to a different mammalian order, Soricomorpha. Mole rats, however, are rodents– they live underground like moles but aren’t from the same order.
  • Opossums. These critters are marsupials, which means their young must live in a pouch within their mother until they’re more fully developed.
  • Rabbits. These were at some point classified as rodents, but after 1912, animal scientists put them in their own order (Lagomorpha) because their teeth are different from rodents.
  • Raccoons. They were once placed in the same animal category as bears, but now have their own genus (Procyon).

A Final Word on Rats, Mice, and Rodents

Not all small furry scurrying wild mammals are rodents, and not all rodents are household pests. In fact, many rodent-type creatures are kept as pets, or even bred for scientific research or even food (in some places). 

Of the many rat and mouse species in the world, three are more commonly associated as pests to be taken seriously: the large Norway rat, the more limber roof rat, and the diminutive little house mouse. 

These three rodents are notorious for sneaking into our homes and helping themselves to our food supply, even potentially causing damage by chewing on furniture or even wires or cables. 

Being able to tell the difference is very useful for extermination professionals, as they are able to employ the best possible measures to counter or control these nuisance pests.