12 surprising facts about rats

1. Rats can control their bladder

Yes, really. It may not sound surprising but an alarming amount of people assume rats have no control of where they pee. Some people even believe they don’t have bladders at all.

In actual fact rats can be very fussy about where they pee – pet rats will often use a particular corner and are very easy to toilet train (just get a ferret-sized litter tray and fill with a different substrate to what’s on their floor – paper cat litter is ideal). They tend to pee to mark their territory, so if you’re a fancy rat owner and your rat pees on you consider yourself owned, they’re saying you belong to them.

2. Rats are exceptionally clean

For an animal so often associated with sewers and rubbish bins rats are actually very clean. They spend several hours a day cleaning themselves and cleaning others is a social bonding experience, sometimes going into extreme cleaning mode as an act of dominance on a family member.

Rats also have sensitive noses (more on that below) and are particularly sensitive to unpleasant smells that can cause respiratory distress.

If you have pet rats consider including a clip-on water dish (the kind sold for birds) as well as the water bottle – chances are you’ll observe your rats perched on the edge and washing themselves with the water.

3. A rat's sense of smell is incredible – and it saves lives

Never underestimate a rat’s nose! These little rodents have one of the best-known noses, with 1,207 olfactory receptor genes according to research carried out by the University of Tokyo. This is just behind elephants (1,948) but a long way ahead of humans (396) and dogs (811).

This is probably because rats evolved a nose to sniff out lots of hidden food in the undergrowth, while our ancestors were busy evolving colour vision to pick out ripe fruit in the trees above. The rat’s nose is so good it has helped clear Mozambique of landmines and they are now clearing landmines in Cambodia, Zimbabwe, and Angola.

The rats themselves are too small to set off the landmines so they’re perfectly safe, they simply indicate where explosives are buried so they can be detonated safely.

Rats are also sniffing out tuberculosis much more efficiently than microscope tests, in fact microscope tests are only 20% effective for patients with HIV, whereas rats pick up 70% of cases, even alongside HIV infection – this is vital in countries such as Tanzania where four in 10 people with TB are HIV-positive.

Meanwhile in the Netherlands police have trained rats to sniff out drugs, explosives and counterfeit cigarettes.

4. Rats are very sociable

In the wild rats live in family groups, and pet rats should be no different. They need company so it’s best to get them in pairs or more - more is preferable to avoid a lone survivor if one dies unexpectedly - and they will go through a period of mourning when one of their family dies.

In the wild rats tend to live in groups of around five, but will often live in close proximity to other rat families. Rats also come to love human company and will answer to their name, but much of their willingness to accept humans will come from their early days so it’s best to get pet rats from a reputable breeder or rescue.

Adult rescue rats will take a bit more time getting used to you, but it will be worth it in the long run.

5. Pet rats are just like wild rats

“But it’s a pet one isn’t it, not a wild one?” is a phrase most rat owners have probably heard at some point. People who get squeamish about rats might not like it but actually ‘fancy rat’ is just the domesticated brown rat, Rattus norvegicus. They might have developed an array of colours, patterns, fur types and a calmer disposition over the years but they’re still the same species and can breed with their wild cousins.

In Europe fancy rats were originally domesticated for the blood sport rat-baiting, where punters would bet on how many rats a terrier could kill in a certain amount of time, but they gained popularity as a show pet in the early 20th Century.

Rat owning and showing fell out of favour until the 70s, but after increasing entries from rat owners at mouse shows the National Fancy Rat Society was formed in 1976, and the first ever all-rat show was held in 1978.

In Japan, however, rats were kept as pets as far back as the Edo period (1603-1868) and research carried out at Kyoto University in 2012 found that all albino rats descended from a single ancestor, suggesting that domesticated rats might have been taken from Japan to Europe and the Americas to be used in rat baiting and laboratories – which would explain why hooded rats (a fancy rat with a white body and coloured head) were often referred to as ‘Japanese hooded’ rats.

The ‘dumbo rat’ is a fancy rat with large, round ears on the side of the head that gives them a cute teddy bear look that has made them very popular as pets. Fancy rats without this ear mutation are referred to as ‘top ears’.

6. There’s a monument to rats and mice in Russia

A six-foot tall bronze mouse is situated in the courtyard of the Institute of Cytology and Genetics in Novosibirsk, Russia. It’s designed to commemorate the rodents used in animal tests and shows a mouse knitting a DNA double helix, little pince-nez perched on his nose. Between 85 and 95% of animals used in laboratories are rodents, including rats, mice, hamsters and gerbils – that’s about 3.33 million rodents per year in the UK and around 100 million in the USA.

Although there is ongoing research into alternatives, the number of animals used each year has only been increasing. A US study in 2015 found numbers had increased by 75% in 15 years. There are different varieties of rats used in labs – such as the biobreeding or BB rat which is diabetic, the Brattleboro rat which has kidney failure, RCS rat which has retinal degeneration and the Zucker rat, bred to be obese, but they are all the same species of brown rat.

7. Rats can’t throw up

Rats can’t vomit or burp and they rarely get heart burn. This is because the stomach anatomy is so different from vomiting species such as humans and dogs – they have an extremely strong gastroesophageal barrier that makes it pretty much impossible to vomit.

This is part of the reason rats are picky eaters – they use their incredible sense of smell to sniff out suspicious foods and when trying new foods they’ll often eat just a tiny amount at time to see whether it makes them ill or not, and if they make a bad judgement will perform pica, or eating non-food items, to help settle their stomachs – clay is their preferred choice of indigestion medication. Other animals that don’t vomit include rabbits, mice and guinea pigs.

8. Rats laugh, but we can’t hear it

Rats are very playful animals, as anyone who has ever watched young rats playing at the river will know. They like to run, jump and play fight. Pet rats will often play wrestle with their owner’s hand, and they get the giggles.

Rats communicate at a higher frequency than us, at about 50 kilohertz or higher, so we unfortunately can’t hear their laughter without the help of a bat detector device. Estonian neuroscientist Jaak Panksepp did just that when he researched his paper Behavioural Brain Research over a period of many years spent tickling rats. He found out rats are particularly ticklish in their nape area, that they will seek out the human hands they know will tickle them and that the rats who laughed the most were also the most playful generally.

He also found they would stop laughing when conditions changed – such as bright lights coming on or the smell of cat wafting in. So far the only other non-human animals who have been proven to laugh are primates such as bonobos and chimpanzees, and there’s research to suggest dogs and dolphins both perform something akin to laughter too.

9. They might not have had much to do with the Black Death at all

Anyone who has sat through a history class will have heard it before – the Black Death, the bubonic plague outbreak in the Late Middle Ages that killed a third of the population of Europe, was caused by fleas carried by rats. But was it really? Research actually suggests the cause was more likely our own parasites. Rats do carry the bubonic plague they are also killed by it, but during the Black Death there were no reports of mass rat die off like there have been during other outbreaks.

The outbreak also spread much more rapidly than outbreaks spread by rats have done in more recent times, suggesting that the Black Death went straight from human to human, resulting in a particularly quick and deadly spread. We may never know the exact cause of the Black Death but we do know the plague virus Yersinia pestis can be carried by a variety of animals – including cats, dogs, camels, sheep, goats, chipmunks, squirrels and yes, humans.

In fact over 200 animals can carry Yersinia pestis, and during the small bubonic plague outbreak in Madagascar in 2013 infected Pulex irritans (human fleas, otherwise known as house fleas) were discovered. So while the jury is still out on the role rats played in the Black Death let’s not hold it against them, especially in light of the lives they have saved in other ways.

10. They can be trained (and there’s a Rat Olympics… kind of!)

Rats are easy to train and can be trained in a similar way to dogs. Like dogs they are very food orientated, so will do anything for a tasty treat. They are also sociable so they like the interaction they get from doing activities such as fetching, jumping, and coming when called.

The psychology department at Nebraska Wesleyan University has hosted the Xtreme Rat Challenge as part of its final project for students of its Basic Learning Principles class for many years, initially under the name Rat Olympics until a court ruling decided that ‘Olympic’ is not a generic word and the thousands of small competitive events using the term should not be using it.

11. In the Chinese zodiac rats are considered intelligent

According to the Chinese zodiac legend when the Jade Emperor invited the animals to his party the Rat took a ride on the Ox and jumped off just as they arrived, making him the first to arrive. Rats are seen as intelligent, practical and quick thinkers, capable of surviving whatever life throws at them – whether that’s earthquakes, famine or war.

Because of their breeding rate success they have also been regarded as bringers of wealth and have been worshiped as fertility symbols in China. As well as having animal symbols the Chinese zodiac also has elemental signs (water, wood, fire, earth and metal).

12. There’s a rat temple in India

The Karni Mata Temple in Rajasthan, India, is famous for its holy rats, known as kabbas, and visitors travel from across the country to pay their respects to the 25,000 black rats living there.

Karni Mata was a Hindu warrior woman and sage who lived some time between 1387 and 1538 and she was believed to be a reincarnation of Durga, the Hindu goddess of war. Her followers are believed to be reincarnated as rats and many people visit to pay their respects to their ancestors. Seeing a white rat at the temple is a particularly good omen as they are believed to be reincarnations of Karni Mata or her sons.

Great care is taken of the rats at the temple – visitors must remove their shoes before entering and predatory animals are kept out, and it's even said that if a visitor kills a rat they must replace the rat with a gold or silver statue. This isn’t the only time rats feature in Hinduism – Ganesha is often pictured riding on the back of a rat.