Difference between rats and mice


What is the difference between a rat and a mouse?

There are just three species of rat and mouse that are by far the most prevalent and important pests in homes and businesses worldwide due to their ability to adapt to the human environment. They are the:

•  Black rat – Rattus rattus

•  Brown rat – Rattus norvegicus

•  House mouse

It is essential to control them as they are major pests of homes and business handling food and they can spread a large number of diseases.

Do you have a rat or mouse problem? Get expert help to eliminate rats or mice in your home or business.  Contact us now!

All rodents have the common identifying feature of a pair of incisor teeth in the upper jaw. Their other characteristics and behaviours are different, however, and give us a number of options for identifying them. Here are six features that show the differences between rats and mice:

•  Physical appearance

•  Eating habits

•  Where do rats and mice live

•  Footprints and trails

•  Droppings

•  Breeding behaviour

Physical appearance of rats and mice

Rats and mice to the inexperienced eye have similar body shape, legs, tail, nose and ears, but a closer look at their body characteristics shows that there are differences in their sizes and features that you can use to distinguish these pests.

Black Rat

•  Slender body

•  Adult weight up to 340 gm

•  Adult length up to 205mm body + 255mm tail

•  Tail much longer than head and body

•  Large thin ears which reach middle of eye when bent forward

•  Long pointed nose – (more rounded in juvenile)

•  Charcoal grey to black or light brown above, cream or white below; sleek smooth coat

•  Smaller in size than the brown rat

•  A young rat has distinctly larger feet and head compared to the body than a mouse .

Brown rat

•  Thick-set body

•  Adults weigh up to 480gm

•  Adult length is up to 255mm body plus 215 mm tail

•  Tail shorter than length of head and body

•  Paler colour underneath the tail

•  Medium sized hairy ears

•  Blunt nose with long whiskers

•  Grey-brown above, white to grey below; shaggy bristly fur

•  Larger in size than the black rat



•  Slender body

•  Weigh up to 25gm

•  Length 30-100mm body + same length tail

•  Large ears

•  Mice are usually light grey or brown in colour with a lighter shade on their bellies

•  A mouse can be confused with a young brown rat, but the mouse has larger ears and longer tail compared to its body length than the rat.

What do rats and mice eat?

Both rats and mice are omnivorous, but the brown rat and house mouse prefer cereals, while the black rat prefers fruit and foods with high moisture content.

Black Rat

•  Prefers moist fruit

•  Cuts grain when eating, giving the appearance that is has been chopped

•  Drinks about 30ml water a day

•  Tends not to eat at the same location on consecutive nights. This makes them more difficult to control, requiring many small baiting points using moist food, which only remains edible for a few days before needing replacing

•  Shows neophobia, a fear or avoidance of new foods or changes to their environment. This means they are slow to take new bait or accept new objects such as traps.

Brown rat

•  Prefers cereals

•  Cuts grain when eating, giving the appearance that is has been chopped

•  Drinks about 60ml water a day

•  Tends to seek food in the same places, making baiting easier

•  Brown rats show neophobia — a fear or avoidance of new foods or changes to their environment. This means they are slow to take new bait or accept new objects such as traps.


•  Prefers cereals

•  When eating it ‘kibbles’ the grain by removing the outer husk to eat the white endosperm inside

•  Tends to seek food in the same places

•  Doesn’t need to drink water but will drink about 3ml a day if available

•  Mice are inquisitive and readily accept new food, often in preference to old ones

•  Mice will visit multiple food sources a night if available, and if only one source is available will visit it around 200 times a night, eating only about 20mg each time.

Where do rats and mice live?

Black Rat

The black rat is very closely associated with humans and is common in urban areas. Being very agile climbers, they prefer to live in roofs, cavity walls, trees; as well as in scrapes and burrows around farms, making nests of shredded materials.

Brown rat

Brown rats shelter under bushes, in sewers and other urban sites. They also make deep burrow systems in the soil, especially near water in more open areas or next to solid objects and structures. They shred available material for making their nests.


Mice usually live on the ground and nest in burrows when outdoors. Indoors they will make nests in almost any place that is undisturbed, such as furniture, boxes, under floorboards, in attics. They will shred material such as paper to use for nesting material. They are agile and can climb to search for places to shelter.

Footprints and trails of rats and mice

Black Rat

Black rats tend to walk on their toes and the surfaces that the black rat travels along show separated smudges.

Brown rat

The surfaces that they travel along build up continuous dirty smudges from being brushed with their oily fur.
Brown rats tend to walk on the pads of their feet and leave footprints and tail marks in dusty areas — or where talc or flour has been sprinkled to detect them.


A mouse obviously has a smaller footprint than a rat. In heavy mouse infestations, grease from the body combined with dirt and urine can build into small pillars. These can remain for a long time, so may not indicate a current infestation.

Droppings of rats and mice

The droppings of the three types of rodent differ in size and shape, according to the body size. Rat droppings are often mistaken for mouse droppings, but are much larger.

Black Rat

Black rat droppings are up to 15mm long. They are sausage shaped, a little smaller than brown rat droppings. Black rat droppings are more regular in form with a banana like curve and pointed ends.

Brown rat 

Brown rat droppings are up to 20mm in length and typically a tapered, spindle shape – resembling a large grain of rice.


Mouse droppings are 3-8mm in length, and are often found scattered randomly during an infestation. The droppings are granular in shape, black and are found near nesting areas.

Breeding behaviour of rats and mice

Mice reach sexual maturity earlier and produce larger litters at a more frequent rate than rats. The new-born of all three rodents are blind, hairless and completely dependent on the mother for feeding and protection.

Black Rat 

•  Litter size: 5-10

•  Number of litters per year: 3-6

•  Time to maturity: 7-8 weeks

Brown rat

•  Litter size: 7-8

•  Number of litters per year: 3-6

•  Time to maturity: 10-12 weeks

House mouse

•  Litter size: 4-16

•  Number of litters per year: 7-8

•  Maturity: 8-12 weeks

Need help with a rat or mouse problem? Get expert help to eliminate rats or mice from your home or business today.  Contact us now!