To the amateur observer, mice and young rats are the same. They’re small, furry rodents which come out at night and cause trouble around the house. If you notice droppings and chewed-on cables, you really don’t care about which one exactly you’re dealing with, as long as you manage to catch it.

However, knowing what kind of rodent is giving you trouble and sleepless nights is important, in order to determine the right way to dispose of the little critters. The differences between a rat and a mouse are many as you will read in a second.

Table of Contents:


In this post we will be looking at the most common species of mice and rats, which populate the UK. Those two are as follows:

  • House mouse (Mus musculus)
  • Brown rat (Rattus norvegicus)


In terms of colour, both rodents look alike, that’s why you should consider other characteristics such as:

Size and Weight

The ordinary house mouse can reach a length from 5cm (2 inches) to 10 cm (4 inches). That’s from the nose to the base of the tail, while the tail itself can be as long as 10 cm (4 inches). The average weight of this rodent is between 40g and 45g (1.4–1.6 oz).

The brown rat, also known as the Norway rat, can reach a length between 15 and 28cm (5.9 to 11.0 inches), while its tail can be as long as 10cm to 24cm in length (4-9 inches). When it comes to weight, this rodent can be as heavy as 140 to 500 g (4.9 to 17.6 oz).

Shape of head

Let’s start with the snout. A mouse’s nose is triangular-shaped, whereas a rat’s snout is more blunt. This gives their heads a different look, the mouse’s being more pointy compared to the rat’s.

Rats have bigger ears than mice, but not in relation to their bodies. That’s why when you look at a mouse, you tend to notice their ears more. They look floppy and somewhat big for their bodies.


A mouse’s tail is very thin and covered in hairs, whereas that of a rat is always hairless.

How do you distinguish a grown up mouse from a young rat?

  • The house mouse has larger ears and longer tail compared to its body length than the rat
  • A young rat has larger feet and head compared to a mouse

Diets and Eating Habits


This rodent prefers seeds, cereal grains and generally anything sweet. However, if certain conditions arise, the mouse will not hesitate to eat whatever is available including meat. As far as water goes, mice don’t need much of it. They usually get the needed amounts from the food they consume, but will drink about 3ml if the opportunity presents itself. They also tend to seek food in the same place they first found it.


Rats are omnivores, meaning they eat anything, however, their preferred food is meat. They even eat mice and that’s not in extreme cases, either. They would scavenge through your trash looking for leftovers and even attack insects. Rats drink about 30ml of water a day. They tend to look for food at different places, which makes them harder to catch.


It can be rather difficult to distinguish mouse from rat droppings, or any other kind of pest dropping for that matter. The place where you’d most often find them is along walls, but they might look like dirt and not like what they really are. Always keep in mind the size.

Mice faeces are between 1/8 – 1/4 of an inch long, smooth, elongated and with pointed ends. Mice produce anywhere between 50 and 70 pallets every day, so you will usually find them in groupings. The areas of your home, where you’re most likely to find droppings, are the attic, closets and areas near food, such as pantries and kitchen cabinets. However, you might also find mouse poop in crawl spaces and air vents.

Rat feces:

Are between 5/8 inch long, curvy and as large as an olive. Rats produce from 35 to 50 brown pallets a day and you are likely to find them in large groupings, as well. The places where rats poop include attics, where the droppings usually get stuck to the insulation, along garage walls, behind storage shelves and behind boxes.


Mice and rats have some significant character differences when they’re not busy chewing on food. Surprisingly, mice are bolder and more curious than rats. They would usually explore new areas, where they’ve never been before. This is important, because it’s easier for them to walk into your carefully set-up trap.

Rats on the other hand are very careful and definitely not explorative. They tend to stick to routes they know are safe. When setting up a trap, you need to know these routes, otherwise the vermin will not go near it.

Af far as nesting goes, mice can easily inhabit all parts of your home even your attic, because they’re skillful jumpers and climbers. Brown rats, on the other hand, prefer the low level parts of your home such as basement and crawlspace.


Both rodents breed throughout the entire year with slight differences in their breeding patterns.

House mouse                   

  • Size of litter: 4-16 pups
  • Litters per one year: 7-8
  • Gestation period: 8-12 weeks
  • Sexual maturity: 5 weeks after birth

Brown rat                           

  • Size of litter: 7-8 pups
  • Litters per one year: 3-6
  • Gestation period: 10-12 weeks
  • Sexual maturity: 5 weeks after birth

Hire a Fantastic pro

If feel there’s an infestation going on in your home, but you have trouble determining what you’re dealing with for sure, give us a call. The Fantastic pest controllers will make a full inspection and find out what kind of a nasty rodent is eating your food or trash. You will either need mice or rat control, but not both. Call us today for an inspection!


  • Rats are larger than mice
  • Mice have bigger ears in relation to their body
  • Mice love to explore and thus, can be trapped more easily, while rats are fearful and won’t fall for your trap once they discover it.


What is your experience? Have you ever had rodents infest your home, only to wonder whether they’re mice or rats?

Image source: depositphotos / Holger Kirk, Szasz-Fabian Jozsef, torook

  • Last update: August 21, 2019

Posted in Pest Problems

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