Main Differences between Rats and Mice

About rodents in general

Rodents are mammals, which are characterised by a single pair of continuously growing incisors (front teeth). They are the most diversified mammalian order and live in various terrestrial habitats, including human-made environments.

Rats and mice are rodents that can transmit various diseases to humans such as leptospirosis, murine typhus, rat bite fever, plague, etc. They are highly ferocious, adaptable to changing environments, and have a high reproductive rate.

However, they have poor visual acuity and colour blind, relying on their extremely strong senses of hearing, touch, taste, and smell. They are active climbers, excellent jumpers, and swimmers.

Mice vs. Rats: key differences

	House mouse	Sewer rat	Roof rat
Head/body length	7 - 11 cm long	19 - 30 cm long	16 - 24 cm long
Tail	7 - 10 cm	13-32 cm but shorter than full length	Tail is longer than head-body length
Weight	10 - 30 grams	Up to 500 grams	Between 150 - 250 grams
Fur color	Gray / brown-gray	Brown, grey or grey-brownish fur	Black - greyish fur
Droppings	3 - 8 mm	Capsule shaped, ugly, up to 2cm	Banana-shaped, rounded & approx. 1 cm
Nest	Inside - near grain/food storage, in walls & ceilings/floors, behind closets	Outside & underground in sewers or burrows, near water	Inside in wintertime, in attics/basements, garages, under the roof.
Reproduction	7-8 litters/year with up to 16 young	3-6 litters per year with up to 10 young
Food	Prefer cereals grains or plant food.	Omnivores that like plant & animal nutrition	Eats grains, seeds, fruits/vegetables
Enemies	Rats, (wild) cats, dogs, weasels, martens, owls, european polecats, buzzards
Damage	Contamination & gnawing, can't chew through glass/metal	Contamination & gnawing, through concrete, aluminium, wood, glass, electrical wiring...

Behavior differences between rats & mice

One of the key differences between the two types of rodents is that house mice are very curious and tend to explore more, even mouse traps. Whilst, rats are a bit more cautious and harder to catch with bait or traps.

Adventurous mice: mice are inquisitive and will explore their new territory during nighttime in search of food, nesting material, fun and things to sharpen their teeth with, although they won't go too far from the nest (5-10 meters). Along these routes, you'll see grease traces or black smear (belly fat) since they tend to move close to walls or run behind closets and big furniture to avoid open spaces. Mice are less social and usually live in smaller groups or pairs.
Careful rats: rats are more cautious when it comes to exploring their territory. They tend to avoid humans, run around at night and they are very wary of new items such as traps in their paths. Rats are more fearful, but operate in a bigger radius around their nest, about 100 meters. Rats are also more social and tend to live in colonies, displaying complex social behaviors.

Both rodents can swim, jump or climb up rough vertical surfaces. Mice are typically faster than rats.

How to tell if it was a mouse or a rat in your food pantry or supply?

Check out for noises and damaged packaging

If you see some gnawing traces on packaging, shredded paper or you heard gnawing or scrabbling noises at night you know you have a big problem.

Since rats are significantly bigger than mice the noises and damage they make are usually also more noticeable.

Rats are twice as likely to move food

A way to tell these rodents apart is the traces they leave at the crime scene, for example: did you find droppings on the way to a food source or next to it?

Because rats are bigger and stronger or maybe more fearful of getting caught, they tend to move their food to a more quiet, private area to consume it. Mice eat their food at the same place they found it.

Size and shape of droppings

If you have mice or rats at home or in your premises you will find droppings. Mice feces are like grains of rice but black. Rats droppings are bigger and banana or capsule shaped.

You will find them alongside their pathways, such as along walls, behind cabinets, stoves or storage racks, in pantries or under cabinetry or food supply pallets.

Mice also use their distinct urine smell to communicate with other mice, to attract a female, indicate the path to food or warn other males.

What are the differences in nesting behavior between rats & mice?

Where Do Rodents Live

Sewer rats

This type of rat lives in burrows and likes humid environments. Their burrows are underground or near water sources. They are very social animals that live together in large groups.

As their population grows, the burrows and corridors expand and connect to other hideouts. This creates a complex network of underground tunnels. They stay in these burrows during daytime and come up at night to forage for food.

Roof rats

Roof rats like to live indoors in search of warmth and food. They prefer high and dry places to build their nests and are masters at jumping and climbing. It's more likely to have black rats in your building, than brown rats. They also come out at night. Black rats collect a variety of materials to build their nests. These materials may include twigs, leaves, grass, small branches, strips of bark, shredded paper or cloth, and other soft and fibrous materials they can find in their environment.

Mice

House mice build their nests near humans for food supply. In homes, near the kitchen in office spaces, in farms near grain storages and in food industry premises. It’s also quite common to find mice infestations in supermarkets and shopping malls.

In cities, mice are often found in old buildings, where they penetrate through partitions of the wall, ceiling or floors. In new buildings, frequent routes of invasion are supply or ventilation shafts and cracks in façade cladding. They will use just about any kind of soft material or shredded paper to build a nest.

What are the differences in reproduction between mice and rats?

Mice have a much quicker reproductive rate compared to rats. Mice are known for their rapid breeding cycle, and under optimal conditions, they can reproduce at an astonishing rate.

Female mice can reach sexual maturity as early as 6 to 8 weeks of age. Once they become sexually mature, they can produce litters every 20 to 30 days. They can have up to 16 young per litter.

Sewer rats can have multiple litters in a year, typically ranging from 4 to 12 litters. Each litter can consist of 6 to 12 or more pups, but the average is around 8. Sewer rats are ready to reproduce again after 2 to 3 months.

Reproduction rates in roof rats are very similar to sewer rats, with the difference that females are sooner sexually mature but need more time in between their litters.

Mice vs. Rats, who causes more damage?

Having either one of these rodents in your environment can be a reason for concern. With their gnawing, both rats and mice cause severe infrastructural damage, ruin stocked goods and insulation, and destroy electrical wiring which could lead to a fire hazard.

Mice have weaker teeth than rats, so they can't bite through hard materials such as glass or metal. Rats are stronger and gnaw through various building materials including wood, concrete, glass, metal, and more.

It is mainly their urine and feces what can transfer bacteria and diseases such as salmonella or Weil's disease to humans or animals through contaminated food/water and direct or indirect contact (with feces and urine).

Rats and mice themselves are not dangerous, they prefer not to interact with humans. Do not try to catch one with your bare hands because they will fight or bite. This bite can transfer disease. In addition, the corpses of dead rodents in walls or in the attic may also attract other vermin.

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Frequently asked questions about Rats

How big is a rat?
An adult sewer rat is 20 to 30 cm long with a tail that is almost as long as the body. She weighs 100 - 500gr. A black rat is approx. 15 to 24 cm long with an even longer tail (up to 130%).
What do rat droppings look like?
Rat droppings are banana shaped and dark brown. Sewer rats: +- 2 cm long, looks less rounded and shorter than those of black rats: +-1 cm long. If the rat poop is soft or shiny, this indicates an active infestation.
How quickly do rats reproduce?
A female rat can have multiple litters in a year, ranging from 4-12. Each litter can consist of 6-12+ pups, but the average is 8. Given these reproductive characteristics, a pair of rats can potentially produce hundreds of offspring within a year if left unchecked.
What do rats eat and how much?
Sewer rats feed on both vegetable and animal food (rich in protein & starch), such as meat, grain, seeds, snails, larvae, bird eggs,... The roof rat mainly eats vegetable food. A rat eats 20-25 gr./day.
Can rats be kept as pets?
Yes, there are around 65 species of rats in total. Some of them can also be kept as domestic pets. These rodents are highly intelligent and social animals. They can form a close bond with their owner and they can be trained. Do not try to domesticate a wild rat.
Where do rats hide during daytime?
Rats are nocturnal rodents and usually sleep or hide during the day in their burrows, which they build below ground or between walls and on ceilings. If food is scarce, they will also come out during the day.
Are rats dangerous?
Rats are mainly active at night and prefer to avoid people. Rats don't attack humans unless cornered. What does entail a risk is their gnawing damage and urine or feces that causes contamination (food, water,..) and spread diseases.
How do you recognize a rat plague?
You can recognise a rat infestation if you find feces, brown/black smear marks on walls, gnawing damage to stock, material or infrastructure, torn soft materials, odor nuisance or hear nightly scribbling.
Can rats cause a fire or a short circuit?
Yes, because rats gnaw on materials they come across when exploring their environment, the insulation around electrical cables can be eaten, resulting in a short circuit and fire. Learn more on the risks of having rats.
Do rats go away by themselves?
Rats look for shelter, food and water. If they find what they need (nesting places, compost heap, sewers, food leftovers, holes, garbage bins) they will most likely stay.

The Main Differences between Rats and Mice

About rodents in general

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