Interestingly, the words rat and mouse are not actual classifications. These are common names for rodents which look similar. The word rat is used when describing a medium-sized rodent with a long thin tail. Many species of rodents are called rats but they are not closely related at all. These include cotton rats, black rats, kangaroo rats, Norway rats, naked mole rats, pack rats and many others.
The word mouse is used when describing a small rodent with a long thin tail. In a similar way to rats there are also many species which may not be closely related but are still called mice. These include field mice, house mice, deer mice, dormice and many others.
So when you are saying what is the difference between a rat and a mouse it depends which type of 'rat' and which type of 'mouse' you are talking about. Usually when asking this question people are referring to wild rats and mice or pet rats and mice. This would mean Norway rats, Black rats and house mice. Norway rats cannot breed with house mice as they are different species. They are, however, inter-related.
Hey are a few differences between them.
- Anatomical. House mice have five pairs of nipples whereas Norway rats have six.
- Morphology. Norway rats tend to be bigger than house mice. The rat body parts are also larger than those of the mouse. Norway rats have a heavier blunt head whereas house mice tend to have smaller and more pointed heads which are triangular in shape. The rats have small ears compared to the size of the rest of their bodies when compared to mice.
- Genetics. There are 22 pairs of chromosomes in a Norway rat where as house mice have 20. Around 90% of a rats' genes are the same as those of a mouse or a human.
- Droppings. Mouse droppings are similar in shape to rat droppings but those of the rat are larger.
How to tell the difference between a Norway rat and a house mouse on hammertechltd.com
The main difference is size. Mice are much smaller than rats. Rats can be 10 times heavier than mice. Baby weaned rats are larger than the adult mouse. It can be difficult for the untrained eye to tell these apart. A baby rat will have more juvenile features than adult rodents. Heads and feet will be relatively larger than their bodies and faces are blunt with a wide nose. The adult mouse alternatively has adult proportions with a smaller head and nose and more delicate feet.
Dr Toby Bateson for www.hammertechltd.com