Top Ten Hated (But Misunderstood) Animals – 2 – The Brown Rat (Rattus norvegicus)

Oh my word, look how cute it is! Those big eyes (and their eye-sockets on their skulls are ridiculous – always the sign of a cutie), that little twitchy snoot, those whiskers, the little round ears. The brown rat is a cute animal! (credit: Dunpharlain CC-BY-SA 4.0)

Contrary to their Latin name the Norwegian rat did not originate from Norway. Sometimes it’s called the Parisian rat but it doesn’t hail from Paris either. At stages it was believed to have come from Ireland, or to have crossed the channel with William the Bastard (or conqueror, if you prefer) a myth it shares with the rabbit here in the UK.

We could look at this inability to determine the rat’s origin as a big red “Not good enough; see me!” at the top of the homework of humanity but I think it is actually a testament to the rat’s greatest strength; adaptability.

Today is a good day to write about the rat. Like the rat I have been nothing if not industrious. In around 3-4 months I have produced over 100 articles across a multitude of topics all of them, as far as I can tell, of good quality and with a unique voice. But I’m of the underground, and when I dare try to pop my curious little head above the sewer grates, around the corners of those alleys, floors soaked with piss and bin-juice, I see traps. I get disgusted looks, people point and go “Eugh! It’s a We Lack Discipline! Someone should call the council and get it sorted.” And, rest assured, ‘get it sorted’ means using some sort of lethal traps or poison – it means kill it.

Brown rats can actually have mutiple colour morphs, most commonly seen in the domestic subspecies (Rattus norvegicus domesticus) but sometimes in the wild, too. (Credit: sipa via Pixabay)

There are some unloved species I do not relate to, you won’t find them on this list. Even then it’s mostly things like Tsetse flies, mosquitoes or parasitic nematode worms. I should make it clear, as I have done in many of this list. I don’t want them to not exist, no matter how harmful they can be for us. I respect their lives and their way of life. Evolution is like that. The genome has a cruel disregard for anything not important to it.

But the rest of them, especially the ones on this list, deserve more respect than they get. The rat was originally going to be my number one, but in the course of sorting this list out my priorities changed and I learned about something altogether more valuable and yet less well regarded. But even so these species are all ones I can relate to, I can understand. I know what it feels like to always have to hide in the background because whenever you show your face people seem to dislike you. I know what it feels like to work incredibly hard, for little-to-no reward, and for people to only see the worst of what you do and never consider your best. I know what it is like to have an undeserved reputation. It’s why this list came to be. To give information about species we might have one opinion of and tell you why they are actually amazing and what they actually do rather than just pander to your pop-culture opinion that is often rooted in pro-pest control propaganda or a sensationalist media agenda.

To be a little bit of a ponce and quote ‘Othello’;

She loved me for the dangers I had passed,
and I loved her that she did pity them.

I am the Desdemona to the Othello of the rat, the gull, the vulture, the fox, the pigeon and the aye-aye. I see their suffering, I respect their fight, and I love them for it. Like poor Desdemona, too, this love smothers me. Compared to my cat list and my sharks list this has been very unpopular, and in my passionate enthusiasm for these species I am creating conflict where I wanted harmony. Creating enmity where I seek, indeed need, support. I have ever been an outcast so that hardly concerns me. What hurts is when I start to feel like crawling out of the sewer only to find my senses barraged with negativity.

The comment by the photographer mentions how rats are a pest for ‘spoiling grain’ but does not mention they balance out their ecosystem disservice with the ecosystem service of predation on invertebrate crop pests, seed distribution services or consumption of weed seeds. Because nobody does. Everyone wants to hate the rat so much they don’t care what good it might do. Look at this beautiful, chonky rat. One of the first terms used in its description was ‘scourge’. How is this a scourge? (Credit: pete beard CC-BY-2.0)

The brown rat is a member of the order Rodentia and they are successful. They are undoubtedly and by a landslide the largest order of mammals – maybe something like 40% of all known mammalian species are rodents. It’s incredible. This success has been dispersed across the globe, barring a few spots (New Zealand, Antarctica, the far north of the Arctic) rodents have got everywhere. Not only are they widespread but there are rodents filling all sorts of niches. We’ve got tiny rodents like the pygmy jerboa, weighing in at 3g, its body is only around 3-5cm, it looks like a kid’s toy! But they go all the way up to the capybara, which is the size of a large dog, looking like a hulking, long-legged guinea pig.

This be the graph! This is how successful and diverse Rodents are. That big blue chunk? Rodents. Looks about 40-45% of all recent mammals are rodents. (Credit: Public Domain)

The largest rodent ever, Josephoartigasia monesi, it doesn’t seem to have a common name so let’s call it the Biggle Piggle, lived during the Pliocene into the early Pleistocene (around 4 million years ago to 2 million years ago). It was basically another massive guinea pig type (or caviomorph) from South America. We don’t know exactly how big it was as we only have a fossil skull, but predictions based on that give a size somewhere between 500-2,500kg! Split the difference we’re potentially talking a metric ton of rodent, around 900-1000kg. The fossil skull we have is 53cm in length and has 30cm incisors! Blades for days!

Take it with a pinch of salt, as it’s a prediction based upon only a skull, but that massive shadow is an estimated size of Josephoartigasia monesi, possibly the largest ever rodent. (Credit: Prehistoric Wildlife)

There are burrowing rodents, tree rodents, ground rodents, water rodents, spiky rodents, smooth rodents, big rodents, small rodents, cute rodents, and cuter rodents and as far as mammals go, whatever the human ego might want to tell us, they rule the earth.

The genus Rattus itself has over 60 extant (opposite of extinct, so alive) species and new ones sometimes turn up!

So where does the brown rat fit in? We’re talking the jack of all trades and the master of quite a few of them as well.

I’m not even sure I know where to start with the brown rat, it’s so amazing! Let’s go origin story.

Brown rats, despite their Latin name, are believed to have originated in Asia, the region of China seems most likely but there are competing theories as to whether it was North or South.

At some point, usually cited around the 1200-1300CE sort of time, these brown rats found their way out of Asia, likely via trade and much like with the black rat before it.

The black rat (Rattus rattus) was once widespread throughout Europe. However, with disuse of wood-and-thatch building materials and with the better adapative qualities of their cousin the brown rat (Rattus norvegicus) to this new brick-and-mortar world, they became increasingly rare. These two are in a zoo. (Credit:
Kilessan CC-BY-SA 3.0)

What we do know is by the 18th century the brown rat was commonplace across Europe, and was displacing its black rat cousin. From there colonisation spread it around the world. The brown rat is commensal with humans, it means it has found a way to live with us, there’s a mutualism.

There are a couple of theories about this the most commonly accepted being that the black rat is more arboreal – a tree-dwelling species – and the switch from wood-and-thatch building to bricks and mortar meant the black rat lost a lot of its human commensal living space. The brown rat is more prone to burrowing and finding a home in nooks and crannies among earth and rocks so it was much more at home in this new, brick habitat.

The black rat, too, by the way, likely migrated out of Asia through trade.

Origin out of the way, I’m going to avoid the anger and indignation for now and talk about what a brown rat is.

The rat that united the world in joy. The New York Subway Pizza Rat! This little guy painstakingly dragged this slice of pizza down some stairs and I can almost guarantee it was taking it to its family! Awww! (Credit: Matt Little)

It’s a rodent, characterised by their ever-growing incisor teeth, the sharp nibblers they have at the front of their face. I’m sure you’ve all seen a rat! So you know what they look like. Pointy little snoot with whiskers, little round ears, big rodent eyes, after that it’s like a cone of meat with a bump at the rump. They have very long tails, usually roughly equal to their body length.

Look, I know rats have their associations and the power of those associations can affect your psychology in such a way that you can be in denial as to certain innate facts. The innate fact is…Rats are damn cute.

Maybe there are some people out there who just don’t like all rodents. You guys get a pass, different strokes and all that. But if you think hamsters are cute but don’t like rats you’re lying to yourself. If you think gerbils are cute but don’t like rats, you’re lying to yourself. If you go “Awww!” when you see a harvest mouse but you don’t think rats are cute, you’re lying to yourself. The visual signals pass through your eyes, you see a rat, your innate neurological process sends it to the cute-centres and then your damn consciousness, your memory, your learning and association kicks into gear and goes “HOLD UP!” It reminds you of everything bad you have ever heard relating to rats and you just kill the cuteness. In a way you’re literally just spoiling your own happiness. You could be enthused and happy when you see a rat and instead you’re worried and disgusted. You’re screwing yourself!

They’re not just cute to look at, either. I mean sure they sometimes have territorial disputes that end up in quite savage fights to the death but within their communities rats demonstrate a social awareness, a sophisticated hierarchy, complex communicative behaviours involving sounds and postural body-language and they play.

Yes, rats play with each other. They are a playful species and they will tumble around and ‘box’ each other. They will do little happy zoomies and jumps. They even perform allo-grooming, that is when members of the community socially groom each other. Huddling, allo-grooming and booping each other with their noses all appear to be behaviours that are important to rat social relationships.

A short video of rats playing. Play is very important as a social bonding behaviour and also often serves the dual role of training real fight behaviours should rats come into conflict. Rat’s teeth are exceptionally dangerous weapons and so genuine rat fights cause serious wounds or even death. (Credit: Megan LaFollette)

Grooming and allo-grooming (where different individuals groom each other) are actually incredibly important for rats that have incredibly exacting hygiene standards. It might make no sense to you, because you associate rats with sewer trash. Rats, though, work hard to keep themselves clean.

They have a vocalisation associated with happiness, a high pitched chirping sound that they may perform when playing. It has been demonstrated domestically when tickling or petting rats. In the lab it has been stimulated when they know they are about to receive morphine. It’s a happy chirp.

They’re intelligent, too. They can be taught and trained. Observation of wild populations of brown rats, particularly in their food selection, seems to indicate they form different groups or cultures depending on where they are, having different food choices. This is likely learned in their social group. Pet rats can be taught tricks and respond well to learning and teaching by giving off the happy chirps I talked about earlier. It seems they enjoy being stimulated. This may be because of the potential conditioning or promise of a reward, but there is some suggestion rats may be capable of metacognition (thinking about thinking) in which case they could just be happy to satisfy their own curiosity…I vibe with that!

Brown rats prefer to live near water sources, and are actually very adept swimmers. (Credit: Biswarup Ganguly CC-BY-3.0)

I know. I’m trying to avoid talking about it because once I do I’m going to get all sweary and angry. I’ll do my best not to because like the number 1 species coming up this is so pervasive an attitude and opinion that to counter it requires coldness, it requires reason, rationality and logic. I find that hard when even the biological community struggles to get things right.

Like almost every animal on this planet rats are capable of carrying zoonotic diseases (diseases that can spread from animals to humans).

Historically rats have been implicated in the spread of plague, caused by the bacterium Yersinia pestis. This struck Europe in three main waves, the First Pandemic began with the Justinianic Plague and continued between the 6th-8th centuries. The Second Pandemic includes the famous ‘Black Death’ of the 14th century but also includes various outbreaks that occurred between the 14th and 19th centurys and finally the Third Pandemic was a major outbreak mainly in Asia from the 19th into the 20th century. These are just the main, large-scale examples, though. Outbreaks were basically common from around the 4th century and still occur today, albeit often with less severity due to recognition of the disease and modern medicine.  

The rat, and in this case it would be the black rat and not the brown rat anyway, but the rat was never the vector (the carrier or spreader) of the disease. That honour goes to the Oriental rat flea (Xenopsylla cheopis).

The Oriental rat flea (Xenopsylla cheopis) was likely the proximate cause of many outbreaks of plague, however recent research indicates the plagues were of such drastic, and deadly scale, because of transmission via human specific parasites. (Credit: CDC, Public Domain)

As a bunch of shy mammals, rats were always unlikely spreaders. They do their best to avoid human contact.

And let me even let the rat flea off the hook. A study in 2018 (Dean et. al.) studying the Second Pandemic found that models relating to rats and rat fleas simply could not account for the rapidity of the spread and levels of mortality seen across Europe. Using data from 9 different local epidemics they found that of these 7 of them best fit the model of transmission by human ectoparasites (in this case human fleas (Pulex irritans) and body lice (Pediculus humanus humanus)).

So once again we have the dear old Homo sapiens looking for any excuse to blame anyone or anything besides itself for its own misfortunes. The second largest cause of spread is probably human-to-human contact through airborne transmission of secondary pneumonic plague – where the same bacterium infects the lungs. Yeah, it’s likely it starts with a rat flea, but we spread it to each other. As I always make abundantly clear any time I am discussing it, the single most common vector of human disease is humans.

“But rats are dirty, what about all the other diseases?” Who do you know who has ever had a rat-borne disease? Oh they exist, I don’t deny that. They are probably a lot more common in areas with little hygiene infrastructure. But here in the UK, over in the US, how common are the zoonotic diseases carried by rats, and how often are they specifically caused by rats?

The only disease this little-whiskers is spreading is cuteness! (Credit: Public Domain – No known author)

Leptospirosis sees an estimated 50 cases per year in the UK and it’s actually most commonly caught from infected cattle, not rats, according to the UK Government Health and Safety Executive (HSE). Link to PDF.

Rat-bite Fever, caused in the UK mainly by Strepobacillus moniliformis bacteria infects around 1-2 people per year according to, actual official statistics appear hard to find, probably due to its rarity. This generally occurs in people who handle rats on a regular basis for a living.

Cryptosporidiosis is an infection caused by a protozoan parasite, of which around 4,000 cases are recorded in England and Wales per year, mostly related to infection via cattle or sheep, with rats not even getting a mention on the HSE facts page. Link to PDF.

Hantaviruses are common in rats, with around a third of pet rat owners testing positive for hantavirus antibodies in a recent study, yet hospitalisations and treatment for hantavirus and its related complications only affect a handful of people each year in the UK. has more here.

How many people per year are actually getting sick and requiring treatment for rat-borne diseases?

Do you know I looked for the figures and they don’t actually exist? You’d think if rats were such a major health concern there’d be some official statistics, some government data, Public Health England would have some numbers. They don’t. Because it isn’t.

Silly rat! You won’t grow bigger if you stand in soil, that’s for plants! Come on, there is nothing about the appearance of this animal that is offputting or disgusting. They are adorable. (Credit: David Shankbone CC-BY-SA 3.0)

Oh, Rentokil, the extermination business, the people who make a shit-ton of money out of you hating rats, has a wonderful page telling me “rodents are thought to be responsible for more deaths than all the wars over the last 1,000 years.” With absolutely zero citation to back it up. They also tell me that because of the lack of study of some of the infections rats may have that “the threat to human health is greater than previously thought.” Which is presumably why since the 1980s or so most epidemiologists and virologists have been warning of the potential for lethal, global pandemics of mutant strains of influenza and coronaviruses and not, you know, rat-borne diseases.

They warn me that rats carry salmonella, that disease known for being commonly caused by people incorrectly preparing, or having insufficient hygiene whilst handling, raw meat.

But I can find no data on official UK statistics for numbers of cases of treated, known rat-borne disease.

Enjoy a rat eating spaghetti (Credit: The Dodo via giphy)

And I know why.

They’re so rare.

In the UK you’re more likely to get E. coli from a bag of salad than from a rat, you’re more likely to get salmonella from not washing your chopping board that had raw chicken on it than a rat. Frankly of almost anything besides rat-bite fever (caused by bacteria most commonly, if not exclusively, found in rat mouths) you’re more likely to get most of the rat-borne diseases from your own piss-poor hygiene habits, or from other domestic livestock, than you are from a rat. It’s not like they’re sneaking into our rooms at night to piss in our mouths. They avoid us…ironically…like the plague! Yes, rats live in close proximity to us but they go out of their way to stay out of ours. Because we kill them.

I want to stress how much I am keeping a lid on my passionate, combustive temper here because I don’t just want to go on a sweary rant and call you all idiots. There has been a long, concerted anti-rodent campaign. Are they great for a hygienic human habitat? No, they do actually piss and shit everywhere and their piss and shit is bad for you. But actual rates of infection from rat-borne diseases are so ridiculously low because maintaining a clean, safe home pretty much deters rats.

The cost to our healthcare systems from rats is miniscule compared to things we permit, even love; smoking, alcohol, recreational drug use, sports injury, human-to-human transmission of staph infections, strep-throat, bloody kidney stones! There’s no company out there saying “Yeah, kidney stones affect 1 in 7 people, necessitating their hospitalisation and potentially causing further complications – what we do as a business is remove both of your kidneys so you don’t have to worry!”

Not only can you pet it, the rat will enjoy being petted. It may even think of it as an allogrooming behaviour. It may give you little satisfied chirps and squeaks. This little animal is capable of squeezing a lot of love in the 1-3 years on average that they live. It’s sad how little we think of them. (Credit: Kapa65 via Pixabay)

And let’s get something straight. Rats fuck. With an average litter size of about seven, a gestation period of about 20 days and reaching sexual maturity within 5 weeks, rats FUCK. It’s the hydra, you cut off one head and it’s already got six more shagging behind the bins ready to give birth to 42 tiny rats that within five weeks can be shagging themselves! Trying to ‘control the problem’ is almost useless. A rat population can go from one breeding pair into the tens of thousands within a year.

Baby rats, sometimes called ‘pinkies’ look like adorable little thumbs. Rats have litters of seven babies on average, but that number can be as high as 14 in any given litter! (Credit: Alexey Krasavin CC-BY-SA 2.0)

Rats are generalist omnivores. Like pigeons and gulls I’ve talked about before the ecosystem services they provide in terms of literally eating our waste probably save local councils millions of pounds. Millions of pounds they then waste poisoning and killing rats. Poisoning which can affect predators, reducing their numbers and, paradoxically, increasing the rat population.

But the true value of rats to humans is actually immeasurable. That’s not even hyperbole. As model organisms in laboratory settings, lab rats and mice have probably had such a significant impact on the development of modern human medicine that their value runs to numbers of dollars that there is not enough wealth in the world to pay.

Rattus norvegicus domesticus, the subspecies of the lab rats, or the pet (or fancy) rat, was bred from the brown rat. In that time we’ve forced them to have tumours, pumped them full of medications, applied topical lotions and potions, studied their behaviours, manipulated their genetics and furthered the cause of human psychological, anatomical, physiological, biochemical, genetic and medicinal understanding so significantly that human quality of life worldwide has improved. Many of these animals are subject to experiments, and then euthanized, to be cut open, dissected and studied.

Rats in a laboratory. We have bred rats specifically to have high tumour rates, we have performed invasive surgeries on rats to study brain activity, we have given rats drugs, good and bad, we have forced carcinogens on them to give them cancers, we have tested almost every single medicine on them, we have learned much about behaviour through them and almost all of them are destined to be euthanised and dissected. (Credit: Public Domain)

In the development of the medicines that stabilise your heart, maintain your blood glucose, reduce your anxiety, help your depression, balance your hormones, and even assist in understanding and treating your addictions; we owe a lot to rats.

We pay it back for this invaluable service to the advancement of human knowledge with disgust, persecution and disregard.

Everything has its place, that’s for sure. I have species I like and I have species I dislike, but I respect every creature for what it does. Even the annoying one like cat fleas that have probably cost me thousands of pounds I didn’t have over the years! Mosquitoes and midges that cause me untold itchy, swollen misery. As for spiders – I’m literally more likely to square up to a seven-foot MMA-trained man-mountain with aggression before I even approach a long-legged, hairy house spider (again, that’s not even hyperbole, you can get confirmation from people who know me!).

Another beautiful chonker! This is a British brown rat, photographed in Stevenage. I am fairly certain Stevenage is home to worse than this beautiful little creature here! (Credit: AnemoneProjectors CC-BY-SA 2.0)

But there are species out there whose uniqueness means it hurts when I find out they are persecuted, like the aye-aye. There are species that our associations with them are based upon past relationships or superstitions, like the wolf, or the bat. Every species has a reason for the hatred, no matter how much misunderstanding, no matter how misguided it may be.

The rat, though? There aren’t many animals that have put more of a shift in to help humankind and we still treat with disdain.

Yeah, that makes me angry, it makes me want to rant and rave but honestly what I mostly feel is sad.

Rats and humans can, and indeed do, live together in harmony. I think it’s about time we changed our opinion on the humble rat and recognised it for what it is truly worth to us. (Credit: maliciousmonkey CC-BY-SA 2.0)

I don’t think there is a single better way to show the selfish arrogance of humanity than the disregard we show to a species that has sacrificed innumerable individuals to the furthering of our own curiosity and yet, we hate them.

Honestly, we don’t deserve rats. They’re too good for us.

Catch up with the rest of the Hated (But Misunderstood) Animals top ten!
Top Ten Hated (But Misunderstood) Animals : Introduction
Top Ten Hated (But Misunderstood) Animals: Bats
Top Ten Hated (But Misunderstood) Animals: Pigeons
Top Ten Hated (But Misunderstood) Animals: Wolves
Top Ten Hated (But Misunderstood) Animals: Foxes
Top Ten Hated (But Misunderstood) Animals: Aye-Ayes
Top Ten Hated (But Misunderstood) Animals: Pika and Moles
Top Ten Hated (But Misunderstood) Animals: Vultures
Top Ten Hated (But Misunderstood) Animals: The European herring gull

Top Ten Hated (But Misunderstood) Animals: The Wasps


Published by Karl Anthony Mercer

Karl Anthony Mercer is a writer, poet, author, musician and part-time dandy. He can often be found squatting in fields looking at insects (he is an unapologetic wasp fanatic), wandering around museums over-dressed, or hiding in a dank corner singing sad songs on a small guitar. His writing on WordPress consists of MercersPoems - an outlet for his poetry often using natural imagery, gothicism and decadence to explore the struggles of living as an autistic person; and We Lack Discipline - Where he writes about factual, often academic topics he has learned and is interested in (e.g. biology, psychology, Roman history etc.) with an inimitable, often light-hearted and irreverant style. You can support Karl by; Subscribing to the We Lack Discipline Patreon - Or buying him a coffee (he loves coffee!) -

12 thoughts on “Top Ten Hated (But Misunderstood) Animals – 2 – The Brown Rat (Rattus norvegicus)

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: