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Confused Between a Rat and a Mouse? Here's How You Can Distinguish

How Do You Distinguish Between a Rat and a Mouse?
Rats are much larger and heavier than mice. If you are one of many who can't tell them apart, then this article is for you. AnimalSake will compare a rat vs. a mouse, and give you useful tips to distinguish one from the other.
Akshay Chavan
Last Updated: May 13, 2018
Did You Know?
Rats are so intelligent that they have been spotted trying to free caged rats in scientific experiments! Also, when scientists tried to tempt these rats using treats, they first made it a point to free their caged companions, and after that they even shared their treats with them.
Rats and mice, though rodents, are commonly confused for each other. Not only in present times, even the ancient Romans called large rodents rats, and smaller ones mice. Though the words 'rat' and 'mouse' are used liberally, they actually refer to the common Norway Rat and House Mouse, respectively. These rodents are ubiquitous, so much so that it is said that there is one rat for every person in a city like New York. While the basic difference between a rat and a mouse is the size, rats also live longer and are much more intelligent than mice. In fact, it is thought that they share traits similar to humans, like intelligence, which is why they make good pets.

Whenever people complain of rats being seen in their houses, in most cases, the creature seen is actually a mouse. This is because, when comparing rats vs. mice, the latter are more common and make themselves comfortable in human surroundings, whereas rats, if found, are mostly in basements or sewers. The reason why both these creatures commonly cross paths with humans is because of the easy availability of food. In fact, this association goes back thousands of years; their bones have even been found in caves where prehistoric man lived. However, both are known to carry parasites that cause diseases in humans. For keeping them at bay, it's important to be able to tell a rat from a mouse, as is explained in detail below.
Physical Differences
Aspect Rat Mouse
Appearance Large, scruffy appearance Small, smoother appearance
Overall Size Pigeon-sized Sparrow-sized
8-12" long 2-4" long
Tail Thick, heavy Thin, light
Shorter than body Longer than body
Scaly texture Smooth texture
6-8" long 3-5" long
Body Color Gray backs and lighter bellies, become browner with age Brownish gray color with light underbelly, but darker than rats
Head Large as compared to body Small as compared to body
Smaller eyes Larger eyes
Smaller ears Larger ears
Head has blunt nose Triangular head with sharp nose
Weight Heavier at 11-22 oz Much lighter at 0.5-2 oz
Feet Muscular feet Lean feet
Larger hind feet Hind feet are proportional
Have gray feet Have pink feet
Nipples 6 pairs 5 pairs
Brown Rat - Rattus norvegicus
Brown rat
House Mouse - Mus musculus
House mouse
Factor Rat Mouse
Age at Which Breeding Starts 3 months 2 months
Gestation Period 20-24 days 19-20 days
Litter Size Per Year 6 litters with 12 infants in each 10 litters with 5-6 infants in each
Infant Growth Open eyes in 6 days Open eyes in 3 days
Grow fur by 15 days Grow fur by 10 days
Life Span 1½ - 2½ years 9-12 months
  • Nocturnal
  • Generally found in sewers, basements, and underground burrows. May enter the house through sewer lines, which indicates a drainage defect
  • Cautious of new objects in its path, and follows standard routines and pathways
  • Can squeeze through 13 mm holes
  • Intelligent and have a keen sense of smell
  • Aggressive when cornered and may attack by jumping up or standing on its hind feet
  • Not agile or good at climbing, though so good at swimming that it can swim through sewer lines even against the current
  • Make deep burrows
  • Nocturnal
  • Found anywhere in the house, but mostly in nests between double-walls, floor joists, closets, and other enclosed spaces
  • Curious and bold regarding new objects in its path
  • Can go through 6-7 mm holes
  • Keen sense of hearing and smell
  • Timid and will scamper when cornered or will freeze
  • Very agile, can even climb rough vertical surfaces and walk over thin ropes and wires
  • Rarely dig burrows, maximum 1 foot deep. Instead, make nests using soft household materials like paper, cotton balls, and string
  • Are opportunistic predators
  • Omnivores with special preference for meat and high-fat food
  • Consume the entire food item
  • Eat grains, meat, candy, vegetables, furs, leather, cereals, nuts, fruits, insects, snails, fish, pet food, birdseed, dog feces, all kinds of rubbish
  • Require water separately
  • Venture far away from burrows in search of food
  • Needs about 30 g food and 1 oz fluid per day
  • Not predators
  • Mostly herbivores with preference for carbohydrates
  • Mostly nibble at food and do not consume entire items
  • Eat seeds, cereals, nuts, butter, bacon, meat, sweets
  • Obtain water from food
  • Forage for food nearby the dwelling
  • Only needs 3 g food a day
  • Larger, about 20 mm long
  • Shape and size similar to raisins with blunt ends
  • Generally found in groups and less in number
  • Smaller, about 3-6 mm long
  • Shape and size like rice grains with pointed ends
  • Many in number, found scattered
Other Signs of Presence
  • Leaves black marks, called run marks, around openings it enters through, due to oil and dirt lodged in fur
  • Gnaw wiring and wooden surfaces
  • Only signs of presence are sounds made while scampering through walls and ceilings, squeaking and gnawing
  • Do not gnaw as much as rats as canines are not as hard
  • Leave behind a musty odor of urine
In hindsight, if you see a large rodent in your house, it's probably a rat. The size difference holds true even in case of any poop that you may find. If you find black trails and tail marks, your culprit is a rat, while a lingering smell of urine will indicate the presence of mice.