Buzz
Just hearing the word ‘rodents’ can send shivers down the spine. These creatures have been our unwelcome companions for centuries, sneaking in the darkness, scavenging through our trash, and spreading illness. But what makes these little beasts so terrifying? Is it their alien nature? Do they reflect our own darker sides? Or perhaps it’s the thought that, though small, they could be hiding right next to us? The truth is, some of them grow to terrifying sizes. Here are a few of these monstrous creatures.
10. Nutria
The Louisiana bayou is facing an invasion. The culprits: nutria, a 6-kilogram (14 lb) rat from South America. With their insatiable hunger for aquatic plants, these rodents are transforming wetlands into open water. Without the bayou to absorb storm surges, the risk of devastating floods in southern Louisiana grows.
In the 1930s, the family behind Tabasco sauce introduced nutria into the Southern swamps, hoping to create a new fur industry as an alternative to beaver pelts. However, the fur of the Argentine swamp rat failed to match the quality of beaver fur, and nutria fur never gained popularity. Now, the rodents are multiplying uncontrollably.
A culinary initiative called Nutriafest was created to promote eating the invasive rodent. Supporters argue that nutria meat has more protein than beef and less fat than farmed catfish. Despite these nutritional benefits, the nutria is burdened with a terrible reputation. To improve their image, some have rebranded them as “the bayou rabbit” or their French name, ragodin. There are even proposals to serve nutria to Louisiana’s prison population, though there’s a fine line between experimental cuisine and cruel punishment.
9. Laotian Giant Flying Squirrels
Not all giant rodents hide in the darkness. Some take to the skies. Measuring around 108 centimeters (42 in) in length, the Laotian giant flying squirrel is not just the largest of its kind—it’s the largest squirrel, period. The first known specimen was spotted in a bush meat market in Laos, and the true population remains unknown. Only 10 others have been discovered, and all were found in freezers.
Despite their name, these flying squirrels don’t truly fly—they glide. A membrane of skin connecting their ankles to wrists functions more like a parachute than actual wings. Their tails serve as stabilizers, while cartilage rods in their wrists help with steering. Unfortunately, these specialized adaptations haven’t been enough to save the Laotian giant, as the species is critically endangered.
The Laotian giant is the second known species in the Biswamoyopterus genus. The first is the Namdapha flying squirrel, which is represented by a single specimen discovered in 1981 in northeast India. With so few Biswamoyopterus individuals remaining, the full extent of their distribution remains a mystery. Other large flying squirrels, such as the red giant, inhabit areas from Afghanistan to the islands of Southeast Asia. Like all flying squirrels, the red giant is nocturnal and arboreal.
8. Castoroides
Before the infamous sewer rats made their mark, monstrous rodents roamed New York City. The Big Apple was once home to Castoroides—gigantic beavers weighing over 90 kilograms (200 lb) and stretching up to 213 centimeters (7 ft) in length. In comparison, the largest modern beavers reach only 27 kilograms (60 lb).
These prehistoric giants vanished 10,000 years ago, along with other Pleistocene mega-fauna of New York, such as mammoths and saber-toothed tigers. The huge beavers are featured in the folklore of several Native American tribes in the Northeast. For example, the Pocumtuk of Massachusetts tell of giant beavers that were man-eaters. While fossil records don’t tell us if these creatures had webbed feet or flat tails, their 15-centimeter (6 in) incisors remain—prompting questions about whether they used their large teeth to fell trees or tear through flesh.
Modern beavers may not be as massive, but they are no small feat either. These aquatic engineers are the second-largest rodents alive, surpassed only by the South American capybara. In the 1600s, European fashion enthusiasts drove the beavers to near extinction due to their lustrous, waterproof fur, a pursuit that also fueled Canadian exploration. These remarkable animals are capable of felling trees, swimming underwater for up to 15 minutes, and transforming entire landscapes into ponds through their incessant dam-building. Only humans rival beavers in their ability to reshape the environment.
7. Swedish Viking Rats
A giant brown rat recently met its demise in a Swedish suburban kitchen after triggering an industrial-strength snap trap. The rat, over 40 centimeters (16 in) long, had chewed through solid concrete to enter the home. Although the rat survived the trap snapping, it suffocated while attempting to drag the trap back into its lair. While there’s no indication that rats are generally growing larger in developed nations, the Viking rat could be a sign of a disturbing trend: mutant monster rats.
Reports of giant rodents have surfaced across Ireland, the UK, and the US. Experts claim the brown rats are now as large as cats, double the size they once were. Recently, exterminators captured a 61-centimeter (24 in) rat in a Dublin apartment. These rats are not only growing larger, but they’re also mutating. Fast-reproducing and increasingly resistant to poison, these rodents have evolved immunity. Exterminators currently use bromadiolone, but they argue it’s no longer effective. A 2009 study from the University of Huddersfield confirmed that genetic mutations have created poison-resistant “super rats.” The question now is whether stronger, more lethal poisons are needed—and how long until the rats evolve again.
6. Capybara
The capybara is the largest living rodent, roaming the humid plains of South America. These semi-aquatic giants can grow to over 45 kilograms (100 lb), which is roughly the size of a Labrador retriever.
In Venezuela, it’s customary to eat capybara during Easter. Its meat, often described as a mix between anchovy and pork, is considered a delicacy. This practice dates back to the 18th century when the Catholic Church supposedly declared capybara to be a type of fish, allowing it to be consumed during Lent. However, most people may prefer not to know that this large rodent has the disturbing habit of eating its own feces.
Some people have taken to domesticating these creatures. Pet capybaras spend much of their time lounging in pools, and they get along with animals like cats, dogs, and horses. However, they are known to taunt rabbits and become irritated by tortoises. A word of caution: Capybaras can be quite aggressive. Their sharp teeth can cause serious damage, and their bites should never be taken lightly.
Much larger rodents once roamed Venezuela, including a giant found in Urumaco, 400 kilometers (250 mi) west of Caracas. This rodent, known as Phoberomys pattersoni, weighed an astonishing 700 kilograms (1,500 lb) and was a relative of modern guinea pigs. Eight million years ago, these 'Guineazillas' likely roamed in large packs along the banks of ancient rivers. Urumaco was home to all sorts of giants, from the largest turtles to colossal crocodiles, and even enormous, unknown fish. Experts believe these enormous rodents went extinct because their size made them easy targets for predators. In nature, sometimes being bigger doesn’t mean better.
5. The Gough Island House Mouse
Killer rodents have claimed dominance on Gough Island. With a population of two million, these aggressive mice run wild across the isolated island in the South Atlantic. These mice are 50 percent larger than typical rodents and have grown to such sizes by feeding on the chicks of Atlantic petrels, a seabird species that breeds here. But this critical breeding ground for the petrels may soon be lost to these invaders.
On the nearby Tristan da Cunha, black rats have already decimated a separate population of petrels. Without any natural predators on these isolated islands, the invasive rodents are free to multiply unchecked. On Gough Island, these supersized mice have been known to hunt and consume chicks of the Tristan albatross, which are 300 times their size. Studies show that 1.25 million of the 1.6 million petrel chicks born each year are eaten by these voracious mice.
It’s not just remote South Atlantic islands facing the threat of invasive rodents. The Farallon Islands, located 45 kilometers (28 mi) off the coast of San Francisco’s Golden Gate, have gained a notorious reputation for rodent infestations. According to a refuge manager with the US Fish and Wildlife Service, “There are so many mice it looks like the ground is moving...When you stay on the island, they crawl over you while you sleep in your bed.”
Accidentally introduced by fur traders, the Farallon mice now have the highest population density of any non-native island rodents in the world. While everyone agrees something must be done to prevent these mice from preying on the endangered ashy storm petrel, there is much debate on how to tackle the problem. A proposal to carpet bomb the island with pesticides from helicopters has stirred controversy, with many questioning the ethics of using poison and worrying about its effect on other wildlife like burrowing owls that prey on the mice. Additionally, the poison would need to kill every mouse, as a single pregnant female could quickly repopulate the island.
There is a precedent for the successful eradication of invasive rodents on islands. In the Aleutian Islands, Rat Island recently rebranded itself as “Hawadax Island” after biologists used poison to wipe out the brown rat population. Unsurprisingly, Alaskans seem more inclined to accept this approach than those in the Bay Area.
4. Josephoartigasia
In 1981, scientists unearthed a 53-centimeter (21 in) skull near Montevideo, Uruguay. Though it was bigger than a cow’s skull, its defining feature was a distinct pair of incisors. This skull belonged to Josephoartigasia, the largest rodent that ever lived. This colossal creature roamed the woodlands of South America around four million years ago.
Upon further examination, scientists concluded that this rodent was as large as a bull, growing up to 244 centimeters (8 ft) in length and weighing over a ton. With a resemblance to a giant capybara, the Josephoartigasia was more closely related to guinea pigs and porcupines than to rats or mice. Its massive teeth likely enabled it to feed on aquatic plants and fruit, though its diet doesn’t indicate docility. These gargantuan rodents lived alongside dangerous predators such as saber-toothed cats, carnivorous marsupials, and giant, 3-meter (10 ft) birds. Their powerful teeth could have been used for defense or as weapons in territorial battles for mates.
3. Cape Porcupines
The Cape porcupine from southern Africa reigns as the largest among its prickly cousins. Weighing in at up to 27 kilograms (60 lb), it ranks as the third-largest living rodent, only surpassed by the capybara and beaver in size.
Cape porcupines boast more than 30,000 quills, each one around 8 centimeters (3 in) long and incredibly sharp. These quills can detach easily and regenerate, offering an effective defense mechanism in the rodent world. Porcupine quills have been used in crafts and tools for thousands of years, and researchers are continually discovering new uses. For example, studies have shown that porcupine quills can pierce pig flesh with half the pressure of a hypodermic needle. The barbed design of the quills makes removal a challenge, which could prove useful for securing medical implants.
With such formidable natural weapons, it's fortunate that Cape porcupines are peaceful creatures. They are nocturnal foragers, spending their nights searching for roots, tubers, and other treasures on the forest floor. These docile giants are also among the longest-living rodents, surviving up to 20 years in captivity. Cape porcupines form lifelong partnerships, often outlasting human marriages, which is quite a feat.
2. Giant Hutia
More than 100,000 years ago, the Caribbean island of Anguilla was home to colossal creatures: rats the size of bears. These monstrous beasts, called Ambyrhiza or giant hutias, were 1,000 times larger than today's rats. Slow-moving and massive, they had no natural predators. The fossil record shows that there were no other large mammals on the island at the time.
The island that the giant hutia once roamed was much bigger than it is today. During the last ice age, lower sea levels connected St. Barts, St. Martin, and Anguilla, forming a landmass known as Greater Anguilla, which was 12 times the size of the modern island. However, as sea levels rose and the ice age ended, the giant hutia could not adapt to the shrinking land and eventually went extinct, much like the dodo.
Today, much smaller relatives of the giant hutia still live in the Caribbean, though most of them weigh only around 2 kilograms (5 lb), a far cry from their giant ancestors. These modern hutias are particularly common near Guantanamo Bay, where they are nicknamed “banana rats.” The “banana” part of their name refers not to their preferred food, but to the size and shape of their droppings.
1. Bosavi Woolly Rats
In 2009, researchers uncovered a hidden world: the Bosavi crater. Even the local Kasua tribe, who assisted the expedition, seldom ventured into the crater. With walls towering nearly 800 meters (0.5 miles), the Bosavi crater serves as an evolutionary sanctuary. This volcanic depression in Papua New Guinea's highlands harbored 40 species new to science, believed to exist nowhere else on Earth. Among the discoveries were 16 amphibians, a gecko, three fish, a variety of spiders and arachnids, a marsupial, and the largest known true rat. Tentatively named the ‘Bosavi woolly rat,’ this 81-centimeter (32-inch) creature, with its luxurious silvery fur, was remarkably docile, suggesting it had never encountered humans.
While the Bosavi woolly rat holds the title of the largest living rat, even larger versions once roamed Southeast Asia as recently as 1,000 years ago. Archaeologists in East Timor uncovered the bones of a rat from this era that was three times the size of the Bosavi rat. These extinct giants weighed as much as 6 kilograms (13 pounds).
East Indonesia is a major hub for rodent evolution. The giant rat expedition in East Timor revealed the remains of 13 rodent species, 11 of which were entirely new to science. With the region's dense forests and challenging terrain, it’s likely that even larger species are yet to be discovered. The mysteries of what else might be out there remain unsolved.
