Scientist Uncovers A Concerning ‘Mutation’ In New York City’s Rat Population

Rats: these worm-tailed rodents scamper across the city streets all hours of the day, and it’s enough to send a shiver down the spine of even the toughest New Yorker. But one rat fanatic in the scientific community has taken a closer look at these creatures and discovered a hidden truth that is forever changing the way we view these vermin.

Most folks around Manhattan try their best to ignore the gnawing rodents that scurry around every dumpster and subway platform. However, one researcher started noticing some strange behavior among the city’s rats and decided to investigate.

YouTube / Jay Karl

That would be Matthew Combs, who’s spent most of his young life studying ecology and epidemiology at Fordham and Columbia. At first glance, another scientist analyzing rats seems like nothing new.

Fordham University

Rats have been the guinea pigs — excuse the animal metaphor — in countless lab experiments, whether they’re being exposed to various diseases or being sent through a maze. Most scientists view them as basic and expendable.

Tiger CraftSquad / YouTube

But Combs argued rats are a complex, misunderstood species, pointing out, “Despite the fact that rats live right in our cities and under our feet, under our noses, there’s actually quite little knowledge about how they behave in the cities, how they move around.”

This curiosity brought Combs out into the nitty gritty of the real world, enjoying the normally unenviable task of getting up close and personal with vermin. He believed this task could benefit human communities in a big way.

Block Island Times

It’s no secret that rats, living in the dirtiest sections of an environment, harbor all kinds of disease. Most famously, these critters contributed to the spread of the Bubonic Plague in the Middle Ages.

And so Combs spent two entire years trapping rats — temporarily — from various parts of the city. He wanted to get a clearer idea of their movement patterns and their behavior toward each other. He suspected these answers might be hidden inside of the rodents.


That’s why the New Yorker extracted their DNA. With this genetic data at hand, Combs could look into how rat populations spread and bred. He was also curious if any particular rat behaviors were unique to a singular population.


As he studied the DNA sequences, however, a startling trend began to emerge. His research indicated that these rats had adapted to life in New York City in an incredible way. In a certain sense, these animals were a reflection of the urban landscape itself.

Just as New York is separated into distinct neighborhoods, each with its own reputation and culture, the rats across Gotham actually existed in genetically distinct colonies! Combs couldn’t believe the simple truth: there were uptown rats and there were downtown rats.

Wojtek Zagorski / Getty Images

Because each faction had their own common DNA strands, Combs surmised that they rarely intermingled or entered each other’s territory. This fit with his knowledge that rats are homebodies, usually remaining within 400 meters of their homes, “even over multiple generations.”

Gary Hershorn/Getty Images

But Gotham’s unique layout also contributed to the development of these two groups. Midtown, obviously in the center of the island, doesn’t attract as many vermin, so it acts as a sort of buffer zone between the hostile populations.

DC Report

And there are some serious rat hostilities. As territorial creatures, they don’t often welcome when an unfamiliar critter enters their turf. That quality, once again, is quintessential New York. Some larger factions even divide themselves into east and west subsets.


Combs found that the city’s rats are basically living out their own version of West Side Story. But these Sharks and Jets just can’t contently remain in their own neighborhoods because there are always some rodents that defy the tendency to stay put.

The Mirisch Company

The Fordham scientists estimated that 5% of rats are born wanderers that will travel up to 2,000 meters away from their homes. Besides potentially blurring the lines between some rodent communities, these are the animals we really have to worry about.

Columbia Pictures

That’s because they’re the ones carrying germs and bacteria out of their nests and into human areas. If we can shed more light on how they move about, Combs believed, it could go a long way toward preventing outbreaks of disease.

No Place for Normal

Even so, that doesn’t make the more stationary rats any less dangerous. Because of their clustering, if you are near one rat, chances are that you are near a lot of rats. While Matthew often analyzes rats from an epidemiological angle, he shared some surprising views on his test subjects.

Hard Eight Pictures

“The more I learn and the more I read about rats, I think the more I’m able to respect them,” Combs revealed. He could be kickstarting a trend of scientists finding solutions for big problems in small rodents.

Association of Jesuit Colleges and Universities

German researchers at the Max Planck Institute of Neurobiology decided to use the gifts of modern tech to learn more about what goes on in the tiny brains of mice, specifically in relation to their facial expressions. What do they mean?

You know how we humans use facial recognition technology to access our cellphones? Well, these scientists used custom facial recognition technology on mice! It turns out that their facial movements tell a story that we never once considered.


According to Newsweek, the scientists fueled their algorithm with images of mice responding to varying stimuli, which included quinine to instigate disgust, sucrose for pleasure, lithium chloride for physical discomfort, escape to kindle active fear, and freezing for passive fear.

Warner Bros.

Upon examining close-up footage of the mice, subtle changes in their facial expressions became apparent. When mice experienced pain, their noses drooped and their ears pointed downward. When mice experienced fear, their ears lifted upward and their eyes grew wide.

Julia Kuhl / Max Planck Institute of Neurobiology

With each emotion these mice felt, there was one facial expression. Fear, however, spawned multiple facial expressions, including those that expressed pain and those instigated by bitter tastes. 

Sol de Zuasnabar Brebbia

So mice produce facial expressions when feeling — just like us! A fine discovery, but the experts weren’t satisfied. They dug deeper to see if they could detect the extent of said emotional states.

Julia Kuhl / Max Planck Institute of Neurobiology

For example, a thirsty mouse given a sucrose solution to drink appeared happier than a quenched mouse given a sucrose solution. Emotional intensity clearly runs on a spectrum. Scientists still had one question.

Rodent World / YouTube

Were these these facial expressions instant reactions to certain stimuli, or did they correlate with the mice’s internal emotional states? Though the mice looked elated while drinking sucrose solutions, perhaps they were daydreaming about the blissful taste of cheese. The scientists were on the case.

“With our automated face recognition system, we can now measure the intensity and nature of an emotion on a timescale of milliseconds and compare it to the neuronal activity in relevant brain areas,” said co-leader of the study Nejc Dolensek.

@NDolensek / Twitter

They analyzed neural activity in the brain’s insular cortex region (which is associated with emotions) via a florescent imaging technique called 2-photon microscopy. The researchers then excited certain neurons associated with different emotions using light.

National Cancer Institute

Since the neurons and the facial expressions reacted at the same exact time with the same exact level of intensity, it was concluded that these are responses to internal emotions. Maybe those happy mice really were daydreaming about sharp cheddar!

Columbia Pictures

So, based on these results, it’s possible there are individual neurons that could be accountable for animals’ emotions; though the study’s co-leader Nadine Gogolla clarified that this point requires more research.

@NadineGogolla / Twitter

“The authors showed that changes in facial expression are not reflex-like reactions but reflected some of the properties of emotions, such as valence (positive or negative), scalability (graded nature of emotional intensity), and flexibility (ability to flexibly regulate emotions),” said neuroscientists Benoît Girard and Camilla Bellone.

Geneva University Neurocenter

Though neither Benoît, of Sorbonne Université, nor Camilla, of the University of Geneva, took part in the original research, they believe the study “has practical implications in our understanding of social behavior and interpersonal relationships.”

Benoît Girard / ResearchGate

However, the two neuroscientists posed further questions. Considering us humans can fake a smile while internally feeling like the world is collapsing (fake it ’til you make it!), can these tiny rodents perform such trickery as well?

Though they’d have to continue studying the beady-eyed rodents to answer that, Nadine Gogolla relayed, “This is an important prerequisite for the investigation of emotions and possible disorders in their processing, such as in anxiety disorders or depression.”

ALBA Network / YouTube

Gogolla, a neuroscientist, expects that by continuing the study of emotions in mice, scientists might gain a strong foundation for further understanding how emotions connected to anxiety and depression emerge in the brain.

Adam Gault

“We hope that this will ultimately help us to understand how we can interfere with the activity in particular brain regions to ease (people’s) suffering,” Nadine continued.

Mari Nakamura

Though this mouse research is a revelation in the study of animal emotion, the German team knows it’s only the beginning, as every animal is different. We don’t exactly think and feel the same way a rodent that weighs .04 pounds does.

Stanton Short / Jennifer L. Torrance, Courtesy of the Jackson Laboratory

And we bet you’ve never even considered mice as emotional animals to begin with! You likely only see them as vermin. Misconceptions about familiar animals aren’t always based on truth, as the moody prima donna misconception regarding cats is only partially accurate.

Elly Gibson

While you may think your cat, who just hissed at you for no rhyme or reason, is an arrogant rascal, the little ball of fur may see you as a special partner. Kitties are just full of surprises (and hairballs).

Social cognition regarding doggos has been studied for decades. By now we pretty much know that dogs are gentle social butterflies that this cruel world absolutely does not deserve. But the social cognition of cats has been neglected by the scientific community.

Since human babies, puppies, and baby monkeys have all showed signs of being securely or insecurely attached to their parents or guardians after a short period of separation, it got scientists thinking about how kittens would act in this type of situation.

Would separation anxiety plague little kittens? Well behavior studies would soon prove or reject the idea that cats could form secure bonds with their caregivers. Scientists at Oregon State University were on the case.

Washington Post

Just like dogs, cats have been witnessed living in harmonious social groupings, but that all depends on factors, such as early developmental occurrences, resource distribution, and social interaction experiences, according to scientific journal Current Biology.

In their study, those brainy scientists put kittens in their own rooms, with only a human caregiver to keep each one company. They spent exactly two minutes getting to know each other. The kittens were undoubtedly curious about their new surroundings.

Oregon State University

Said caregiver would then get up and exit the room for exactly two minutes, leaving the kitten alone. Those two minutes would give the new friends space to breathe and decompress from their introduction.

The Atlantic

Sure enough, two minutes later, the caregiver would return to the room to greet the kitty once again. Their behavior during the reunion would be telling of their level of bonding. This process is called a “secure base test.”

The findings of the study were published in the scientific journal Cell Press, and the results may surprise you. There’s much to know about felines that probably escaped your mind. They’re complex beings!

“Like dogs, cats display social flexibility in regard to their attachments with humans,” Kristyn Vitale, study author and researcher at Oregon State University’s Human-Animal Interaction Lab, explained of cats’ behavioral habits. But not all cats have the same attachment style.

It turned out that 65% of cats are securely bonded with their owners! The findings show that the relationship continues to be constant in adulthood; the little kittens don’t typically outgrow their connection.

“We found that the attachment bond cats display toward their owners is very similar to the bond dogs share with their owners and even the bond human infants display toward their caretakers,” Krystin disclosed. And we thought they were so different.


On the other hand, some cats form insecure bonds with their owners. The insecurely attached cats showed signs of stress, which involved twitching tails, licking lips, and avoiding their owner at all costs. Somehow, we relate.

Oregon State University

Believe it or not, the felines that leaped into their owner’s lap, refusing to move, were also considered to be insecurely attached. This kind of behavior is an indicator of ambivalence. While they seemed mushy, there was a sense of crippling uncertainty.

Oregon State University

“Cats that are insecure seem to act aloof. There’s long been a biased way of thinking that all cats behave this way. But the majority of cats use their owner as a source of security,” Kristyn said.

Even the kittens that went through a 6-week socialization training course did not deviate from their bond with their master. Some bonds are just unbreakable by nature.

Kristyn even said that cats actually depend on their owners to help them when they feel stressed out. This whole time you’ve likely been thinking that good ol’ Sprinkles only required sustenance, but in reality, Sprinkles needs you for much more than that.

“We’re currently looking at several aspects of cat attachment behavior, including whether socialization and fostering opportunities impact attachment security in shelter cats,” Kristyn relayed regarding future studies.

The Office

We know it sounds bananas, but based on Krystin Vitale’s findings, your cat loves you more than you know. They may show their affection and gratitude for you in odd ways, but they’re not as antisocial and cold as you’d think.

Krystin Vitale’s secure base test findings only prove the unexpected emotional intelligence of our sassy, furry friends. You may think you have your feline figured out now, but there are plenty more surprises lurking behind those mysterious, golden cat eyes.

The Office

We’re sure you’ve been perplexed by your cat’s uber-flexible body, and well, it’s no illusion. They actually have 53 vertebrae on their spines, while a human only has a measly 34. So stop trying to best your kitten during yoga — they’ve got you beat by 19 vertebrae!

2. If cat vs. dog intelligence has ever been debated, consider it resolved: Cats have 300 million neurons in their brains, while dogs have just 160 million. In fact, a cat’s brain is considered to be extremely similar to a human’s brain, so expect a feline uprising any day now.

3. Since whiskers detect distances and movements by the air’s vibration, they’re actually crucial to a cat’s survival in the outdoors. So don’t be too scared if your cat runs off — they have survival tools built right into their bodies!

4. What’s the deal with cats and catnip? Cats naturally have the scent of catnip binded to their nasal passages, so when they get a whiff of the herb, it stimulates the sensory receptors in their brains — and makes them act a little lovey-dovey.

5. It’s no secret that cats spend a majority of the day sleeping. We’re actually pretty jealous of just how long a cat can sleep for, which is at least 12-16 hours a day. Cats just don’t know how lucky they are! 

6. Did you know that cats have dominant paws? Females are more likely to use their right paws while males usually prefer their left. No word yet on if the whole “right brain, left brain” thing exists with cats!

7. The rumors are true, cats can change color! Well, maybe not in the way you’re thinking. Siamese cats have a gene modifier that technically makes them albino, but when they’re introduced to high temperatures, portions of their fur turns gray or even black. 

8. If you want your cat to stop leaping onto the kitchen table, try spraying them with lemon water. Cats are picky eaters and are especially sensitive to bitter and citrus-y flavors, so they’ll quickly learn to avoid the lemony spray. 

9. The next time your partner scolds you for taking too long in the shower, bring up this fact: cats spend 30%-50% of the day cleaning their bodies! Much like us with showering, grooming improves a cat’s circulation and prevents any unseemly odors. 

10. A purring cat can be totally soothing when you’re in a bad mood, but the sound has other surprising healing properties as well. Purring can be restorative to a cat’s health, and it even helps heal problems with bones and tissues. 

11. Be careful when considering a major lifestyle change with your cat. Studies have shown that something as simple as a change in routine can negatively impact a cat’s immune system and make it sick. Even a healthy cat can be affected!

12. Cats really do have 9 lives, and it’s thanks to their interesting bodies. Cats have a “straightening reflex,” meaning that some of the tiny balancing-organs in their ears help tell a cat when they’ll hit the ground and how to land on their feet. 

13. At night, cats often choose to sleep in spots that are high-up and hidden in an effort to remain unseen by potential predators. This is just more proof that modern-day cats are not so different from cats in ancient times!

14. We all know that people can be allergic to cats, but did you know that some cats can be allergic to people? It’s estimated that approximately 1 in 200 cats suffers from asthma caused by dusty and unkempt living conditions. Luckily, cat inhalers exist.

15. If you’ve stepped on your cat’s tail, the high-pitched shriek and bared fangs you get in return is exactly what you’d see in a stray. A cat’s DNA never changes, so when threatened they revert right back to the wild ways of their ancestors. 

16. Humans are unique in how we all have different fingerprints, and the same can be said for cats…sort of. Believe it or not, the sure-fire identifier for a cat is actually its nose! Who knew those little noses were so complex?

17. It may sound like the only thing your cat does is meow and purr, but felines can actually produce about 100 sounds! This certainly furthers the “cats are smarter than dogs” argument, considering how dogs only produce about 10 sounds.

18. Cats need seven times less light than humans to see, especially during the daylight hours. This explains why some cats naturally gravitate towards dimly-lit rooms or closets. It’s also why they’re more energetic at night — they can simply see things easier!

19. There’s another reason cats are so bendy, and it’s not because they’ve been exercising! Felines are born without clavicles, which means they don’t have to worry about bulky bones impeding their movement. This makes them experts when it comes to slinking through narrow passages!

20. If your cats aren’t BBFs, there’s a reason why. Cats develop a “secret language” with humans, a language they do not share with any other cat living in the same space. This means no cuddling and no mingling — they’re basically just acquaintances!

Plenty of cats share their living spaces with a dog, too, because there’s a lot of overlap with cat and dog people. That’s why even feline aficionados are brushing up on these wild dog facts.

1. The word “puppy” is a relatively new addition to the English language. A variation on the French word “poupeé,” meaning doll or toy, it caught on in the late 1500s. Before that? Britons referred to baby dogs by the not-so-catchy term “whelps.”


2. Puppies sleep a ton — sometimes up to 20 hours per day — and for good reason. Rest is essential for their developing body and mind. Even when they reach maturity, dogs catch quite a few z’s each day, usually between 12 and 14 hours.

3. Just like humans, young dogs have baby teeth that fall out and eventually get replaced by an adult set. However, there is still no evidence that any kind of dog tooth fairy exists.

4. Depending on the breed, dogs can have vastly different sized litters. Bigger canines usually have bigger litters, as a rule of thumb. A Neapolitan mastiff owns the current record for giving birth to 24 puppies in 2011.

The West Australian / Ian Munro

5. Can dogs inspire great works of art? Hamilton composer and star Lin-Manuel Miranda would certainly say so. His stage ballad “Dear Theodosia” started out as an ode to his dog Tobillo, a stray pup he adopted in 2011.

6. If you’ve ever met a newborn puppy, you’ll notice that their eyes and ears don’t open for a couple of weeks. This is because, compared to other mammals, gestation periods for dogs are pretty short. As a result, puppies are born not quite fully developed!

7. Rolling Stones guitar hero Keith Richards smuggled a number of things past customs, cough cough, but his cutest contraband was a puppy. After sneaking it past British authorities, he named the pooch Ratbag and treated him to a rock ‘n’ roll lifestyle.

Bent Rej

8. Sure, your dog is friendly, but have you ever worried that they’d like any old stranger just as much as you? One 2005 study will put your mind at ease. Researchers observed that canines are most responsive to their owners, proving there is a definite bond.

9. Sports teams aren’t the only ones with dog mascots. The Spanish city of Bilbao is synonymous with West Highland Terriers thanks to Puppy, a gigantic sculpture outside the Guggenheim Museum. The statue weighs 17 tons and is covered in living flowers.

10. Just like in humans, yawns are contagious among mature dogs — probably as an embedded form of social empathy. Curiously enough, this isn’t the case for puppies! They are undeveloped enough to not react to their owners’ yawns at all.


11. For famed novelist John Steinbeck, a dog really did eat his homework. In 1936, his teething puppy tore apart his lone manuscript for Of Mice and Men. The frustrated author had to rewrite those chapters, much to the delight (or chagrin) of students everywhere.


12. Even though puppies from the same litter are similar, it’s extremely rare to find identical twin canines. The first confirmed case didn’t come until 2016 when a South African veterinarian determined two pups were genetically identical from sharing the same placenta.

Semantic Scholar

13. But twin puppies aren’t the only genetic canine copies out there. Scientists successfully cloned the first dog in 2005, and that practice has expanded into a niche industry of cloning families’ beloved pets — for the hefty price of $50,000.


14. It’s no coincidence that dogs seem sadder whenever you’re eating. They’ve evolutionarily adapted to raise their eyebrows and make their eyes bigger to improve their chances of guilting humans into tossing a scrap of food their way.


15. Seeing eye dogs aren’t the only employed pooches out there. Boston’s Museum of Fine Arts has trained a puppy named Riley to sniff out species of moths and beetles that destroy priceless artwork.

Smithsonian Magazine

16. Attention Dalmatian owners: don’t freak out when your puppies are born without any of the trademark spots! Those only start to pop up as the breed gets older. And Dalmatian puppies aren’t the only ones who’ve surprised owners with their coats…

17. In 2017, several dogs in the UK made headlines for giving birth to green puppies. Was this a rare mutation? Were the pups celebrating St. Patrick’s Day? No, it turns out their fur was temporarily dyed by biliverdin, a pigment naturally found in dog placentas.

18. Don’t freak out if your boss catches you scrolling through dog photos at work. A 2012 study concluded that looking at pictures of cute animals can actually help you concentrate afterward.


19. There was one warm and fuzzy result of the Cold War. Soviet Premier Nikita Kruschev knew that President John F. Kennedy was curious about Strelka, the Russian dog that went into space. As a gift, he sent JFK one of Strelka’s puppies. The Kennedys named her Pushinka, after the Russian word for “fluffy.”

Wikimedia Commons / Cecil W. Stoughton

20. JFK’s one-time political rival Richard Nixon also had a historical puppy moment. While running for Vice President in 1952, Tricky Dick came under fire for using campaign contributions for personal use. He denied these claims in a televised speech and said that the only gift he accepted was their family dog, Checkers.

21. Dogs don’t curl up while sleeping just to look cute, or even to feel more comfortable. This tendency is actually rooted in their instincts to protect their vital organs at night (and to stay warm, of course).


22. Some recent studies have found that dogs usually try to “go to the bathroom” in such a way that they’re aligned with the earth’s magnetic field. Both sexes defecate in the north or south direction, but only females prefer to urinate that way, too.


23. The idea that dogs only see in black and white is a total myth. They can actually perceive a wide range of colors, although it’s more limited than the spectrum that humans can see.


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