Pet mouse facts: surprising things about pet mice

Fun facts about mice

These are the ones that surprise people most. Each comes from a vet reference, a welfare charity or a mouse club.

1. They talk in ultrasound. RSPCA Australia says mice vocalise mostly above the range of human hearing, so you miss most of the conversation.
2. Their tail is a radiator. The MSD Veterinary Manual explains that mice control their body heat by widening or narrowing the blood vessels in their tails.
3. Their hearts race. A mouse's heart beats 450 to 600 times a minute, several times faster than a resting person's.
4. Their front teeth never stop growing. PDSA says mice need things to gnaw to keep them worn down.
5. Orange teeth are healthy. PetMD notes that a mouse's teeth often turn orange-yellow with age, and that is normal.
6. They see poorly but smell brilliantly. The Oxfordshire rescue Crittery says mice have quite poor vision and rely on their sense of smell. Blind mice can live well with a thoughtful cage layout.
7. Grooming is a big part of the day. The RSPCA says mice spend a large part of their waking time grooming.
8. Wild mice cover huge distances. The RSPCA says wild mice travel many hundreds of metres a day, which is why pet mice need so much room to run.
9. They rattle their tails. Crittery explains that mice rattle their tails when angry or frightened, and sometimes when excited.
10. Girls climb, boys mark. Crittery says does like vertical space more than bucks, while bucks may shuffle their bottoms across surfaces to scent-mark.
11. They are clever. RSPCA Australia describes mice as quick learners and trainable, with excellent memories.
12. There is a whole show world. The National Mouse Club was founded in 1895 and still runs championship shows, judging colour, markings, coat, ears, eyes and tail.

What noises does a mouse make?

Mostly ones you cannot hear. RSPCA Australia says mice communicate in a range above human hearing, so to us they seem quiet. The sounds people can hear are gentle chirps or clucks, squeaks, a soft grinding of the teeth and hissing.

At night you will also hear the busy sounds of mouse life: the wheel turning, bedding being dug and cardboard being shredded. For how to read posture and behaviour as well as sound, see our guide to mouse behaviour and body language.

Mouse body facts

A pet mouse is tiny but works at full speed. The MSD Veterinary Manual gives an adult body of 6 to 8 cm (2.5 to 3.5 in), 15 to 18 cm (6 to 7 in) including the tail, and a weight of 20 to 40 g (0.7 to 1.4 oz). Males are usually larger than females. Show mice are bigger: Crittery puts pet mice at about 25 to 50 g (0.9 to 1.8 oz) and show types at 60 g (2.1 oz) or more, and the American Fancy Rat and Mouse Association says a show adult averages 20 to 23 cm (8 to 9 in) from nose to tail tip.

A mouse's normal body temperature is 36 to 38°C (98 to 101°F). Because it is so small, it gains and loses heat fast. The MSD Veterinary Manual gives a safe room range of 18 to 26°C (64 to 79°F) and warns of heat stroke above 30°C (86°F). An adult eats only about 3 to 5 g of food and drinks about 3 to 5 ml of water a day, roughly a teaspoon of each.

Mouse eyes are either black or pink to red. Crittery notes that "pink eye" covers every shade between. Does have ten nipples, according to the National Mouse Club. And mice make two kinds of droppings: PDSA explains that the soft ones, called caecotrophs, are eaten again to get the most from their food.

Mouse breeding facts

Mice are famous for breeding fast, and the numbers explain why. The MSD Veterinary Manual says mice mature at 6 to 8 weeks, pregnancy lasts 19 to 21 days, litters average 10 to 12 and a female can have up to 15 litters a year. She can fall pregnant again within 24 hours of giving birth. The National Mouse Club says litters can top 20. Babies are born hairless, deaf and blind, open their eyes at about 12 days and look like tiny adults within two weeks.

In the wild, The Wildlife Trusts say a female house mouse can produce up to 10 litters a year of four to eight young. That is why pet mice must live in same-sex groups.

Mouse history facts

House mice started out in central and southern Asia and spread around the world alongside people, according to the MSD Veterinary Manual. Along the way they picked up a remarkable history.

• In China, mice were used in religious rituals as early as 1100 BC and were called the "ancient ones".
• In Japan, mice were believed to be messengers from the gods.
• The ancient Greeks worshipped mice and used them to predict the future.
• Sailors and miners took mice into submarines and mines to test the air.
• Mice have been sent into space.
• People in Europe and Asia began breeding mice for their fur and colour, which led to the fancy mouse.

The fancy mouse grew into a hobby with its own clubs and standards. Today there are dozens of colours, set markings and coats such as satin, long hair and curly astrex. Our guide to pet mouse breeds and colours explains them.

What types of mice are there in the UK?

Several wild mice live in Britain. These are the three you are most likely to meet, all described by The Wildlife Trusts.

Facts about deer mice

The deer mouse lives in North America and is a different species from the house mouse. It matters for one big reason: the CDC names the deer mouse as the main carrier of the hantavirus that causes hantavirus pulmonary syndrome in the US. People catch it mainly through contact with rodent urine, droppings and saliva, and symptoms usually appear one to eight weeks later. Never handle wild deer mice or keep one as a pet.

Creepy facts about mice

A few facts are less cute, but all are true and most have a sensible reason behind them.

• They eat their own droppings. The soft caecotrophs are eaten again for their nutrients, which PDSA says is part of a healthy gut.
• Mothers may eat their young. The MSD Veterinary Manual lists too little food or water, overcrowding, too little nesting and loud noise as causes of pups being abandoned or eaten. It advises leaving a new litter undisturbed for at least 7 days.
• A group can quickly become a crowd. With pregnancy at 19 to 21 days and a new pregnancy possible within a day, one mixed pair can become dozens of mice in a few months.
• Wild mice carry disease. Wild rodents can carry parasites and disease harmful to pets and people, which is why pet mice should never meet wild ones.

Facts that make you a better mouse keeper

Every fact above points to a care rule. Ultrasound chatter and a sharp sense of smell are why mice need company and a quiet room. Fast-growing teeth are why they need cardboard and untreated wood to gnaw. Tail cooling and a small body are why the room should stay at 18 to 22°C (64 to 72°F), PDSA's ideal. Fast breeding is why groups must be single-sex. And a short life is why weekly health checks matter. Our full pet mouse care guide puts it all together, our guide to how long pet mice live covers each life stage, and if you are still deciding, read mice as pets first. Already have a group? Our pet mouse names page has over 200 ideas.