What is the difference between a rat and a mouse?

Mice and rats are both a small furry rodents with long tails and beady eyes, but they are also two completely different species with separate characteristics. So what is the difference between a rat and a mouse? Well there are many, but I will list the main ones below, including most obvious one which is that rats are much bigger than mice. I hope that you will enjoy reading about the difference between mice and rats and find my list useful.

Note that the terms ‘rats’ and ‘mice’ aren’t actually scientific terms and there are many different species that are labeled ‘rats’ and ‘mice’ by people. For example, there are kangaroo rats and cotton rats, and dormice and field mice. However, for the sake of argument, I am going to assume that a ‘rat’ in this case refers to the most common type of wild rat that you get around humans in towns and cities, namely the Norway rat (sometimes called the brown rat, Latin name: Rattus norvegicus) and that ‘mouse’ means the most common type of wild mouse that you are likely to see around humans, namely the ‘house mouse’ (Mus musculus). Although it’s a generalization, it’s fair to say that these are the types of wild rats and mice that ordinary people most often encounter and are talking about when they refer to mice and rats.

1. Adult rats are much larger in size than mice. In bird terms, a rat is about the size of a pigeon and a mouse is the size of a sparrow. The rat’s body length is longer, with rats being between around 9 and 11 inches long and a mouse being just 3 or 4 inches. Rats are also over 10 times as heavy as a mouse with an adult male weighing between a half and one pound and a mouse being in the region of a measly half ounce.

2. Rats also have much longer tails than mice. An adult rat tail will typically measure in the region of 7 to 9 inches, whereas a mouse tail is more likely to be between 3 and 4 inches.

3. The other visual clue is that the shapes of the head are slightly different for rats and mice. Mice have small, triangular heads, whereas the rat head is chunkier and less pointed.

4. If you have a wild rodent living in your house and you are not sure what type it is, one way to find out without actually seeing it, is to look out for droppings. Mice droppings are much smaller than rat droppings, measuring around 1/8 inch long and they are pointed at both ends. Rat droppings measure around 5/8 inch long and are curved in shape.

5. There are also some important biological differences between mice and rats in terms of their development. Essentially, young mice develop much more quickly, opening their eyes after around 3 days and having fur after about 10 days, whereas rats open their eyes after 6 days and have fur after about 15 days.

6. Rats also have an extra pair of nipples when compared with a mouse (a rat has 6 pairs and a mouse has 5).

7. My seventh and final main difference between mice and rats is that mice don’t kill rats, but rats can and do kill mice. Rats will actively hunt, kill and eat mice – this behavior is known as: “muricide”.