Rat facts: surprising things about pet rats

What are pet rats?

Every pet rat, from a sleek black rat to a curly dumbo, is a domestic brown rat, Rattus norvegicus. These are the facts about domestic rats that surprise people most.

1. "Norwegian" rats aren't from Norway. The naturalist John Berkenhout gave the brown rat its Latin name, Rattus norvegicus, in 1769. The National Fancy Rat Society (NFRS) points out the brown rat didn't even reach Norway until 1762, so the name was a mistake that stuck.
2. Males are almost twice the size of females. The NFRS gives about 500 g (17.6 oz) for an adult male and 300 g (10.6 oz) for a female.
3. Each rat month is about 2.5 human years. By that sum, used by the RSPCA and Burgess, a three-year-old rat is around 90 in human terms.
4. The oldest pet rat on record lived to 7 years and 4 months. Burgess, citing Guinness World Records, names him Rodney, from Oklahoma.
5. A group of rats is called a mischief. The RSPCA uses the word too, and anyone who has kept rats knows why.
6. "Fancy rat" just means a pet rat. The name comes from the rat fancy, the hobby of breeding and showing them. See our guide to fancy rats and our rat breeds and colours guide.

Fun facts about rats' bodies

There is more on eyesight in our guide to what rats can see, and on teeth in our rat teeth care guide.

Cute facts about rats

• Rats laugh. The RSPCA says happy, excited rats make high-pitched squeaks too high for human ears.
• They purr with their teeth. Soft grinding, called bruxing, usually means a rat is content, a bit like a cat purring (PetMD).
• Their eyes boggle when they're happy. Strong bruxing makes the eyes vibrate in and out, because the jaw muscle runs behind them (PetMD, RSPCA).
• They popcorn. Young, happy rats leap and twist in the air when they play (RSPCA).
• Their ears blush. Pink ears are a sign of a happy rat (RSPCA).
• They sleep in a heap. Rats groom each other daily and love a "rat pile" at bedtime (RSPCA).
• They give "kisses". The AFRMA says a rat licking your hand is a sign it likes you.

Our guide to rat sounds explains what every squeak and grind means.

How clever are rats?

Very. The RSPCA describes rats as quick learners with excellent memories, and says they can learn to come to their names, give high-fives, fetch a ball and roll over. It even says rats can count to 10. The NFRS calls pet rats "the most intelligent, affectionate, and responsive of all the small rodents".

A bigger cousin, the giant African pouched rat, has been trained to sniff out landmines and tuberculosis, finding thousands of mines in Tanzania, Mozambique, Angola and Cambodia, according to the RSPCA.

Fancy rat facts from history

Pet rats have a stranger history than most pets. All of these come from the NFRS's history of the rat fancy:

• In Japan, rats were kept and bred from around 1654, and a guidebook from 1789 describes breeding them for different coats.
• Paris had a show of trained rats walking a high wire in 1667.
• Jack Black, rat catcher to the Royal Parks in London from 1825, kept and bred unusual coloured rats he caught.
• Victorian writers believed the first pink-eyed white rats came to England with a travelling showman.
• Mary Douglas was an early pioneer of showing rats, writing about them in 1909.

Showing still goes on today: the NFRS in the UK and the AFRMA in the US both run shows and keep breed standards.

Brown rat and black rat facts

There are two wild rats in the UK, and they are very different animals. Pet rats come from the first.

The NFRS notes that the dates are mostly based on old anecdotes, so treat them as best guesses.

Kangaroo rat facts

Kangaroo rats aren't close relatives of pet rats at all. They are small North American desert rodents in a different genus, Dipodomys, rather than Rattus. The National Park Service at White Sands, New Mexico, describes two species there, Merriam's and Ord's kangaroo rats:

• They can leap about 2.4 m (8 ft) on their long back legs.
• They rarely, if ever, drink. They get their water from the dry seeds they eat.
• They carry seeds home in fur-lined pockets on the outside of their cheeks.
• Some species drum their big back feet on the ground.
• When a predator comes close, they kick sand in its eyes and bound away.
• They spend the day underground and pack the burrow entrance with sand to keep it cool and damp.

Bad and creepy facts about rats

Rats have a scary reputation, and a few facts are worth knowing whether you keep them or not.

• They breed fast. Pregnancy lasts only 21 to 23 days (RSPCA), and the NFRS says a female can mate again straight after giving birth. VCA says a female can have up to seven litters a year.
• They hide pain. The RSPCA warns rats may suffer a lot before you notice, which is why daily checks matter.
• They can carry germs. The CDC, quoted by the RSPCA and Humane World for Animals, advises homes with children under five, pregnant people or anyone with a weakened immune system not to keep pet rodents. Wash your hands after handling.
• They can bite when frightened. Well-handled pet rats rarely bite, but children should be supervised (RSPCA).
• Wild rats live short, hard lives. Jollyes gives six months to a year, against two to three years for a pet.

For pet rats, the rest of the story is in our guide to rats as pets, our rat lifespan guide and the pet rat care hub.