Rat Bomb: Farming’s Death of a Thousand Bites
What sex-crazed, eating machine gorges on a portion of profit from every farm, ranch, dairy, hog barn, feed mill and grain elevator on the planet? Guess rat, and guess right. Without fail, each year the agriculture industry endures the death of a thousand bites from a rodent that reigns supreme as a survivalist in the animal kingdom.
All told, rats rack up to $20 billion in damages to the U.S. economy each year, and agriculture pays a hunk of the bill, covering for damage to field crops, stored grain, equipment, building structures, and much more. Coast to coast, rat presence is near-ubiquitous at some level on agriculture operations of all types, but beyond the propensity to eat, gnaw and burrow, most producers know very little about a rat’s phenomenal ability to thrive in all quarters. Know thy enemy—especially one that has sex dozens of times per day.
The Rat Czar
Ironically, understanding the impact of rats on agriculture requires a trip into the urban realm of Bobby Corrigan, the “Rat Czar” of New York City. Simply, no one knows rats like Corrigan. A rodentologist with 25 years of experience, his reputation extends far beyond U.S. borders and carries him around the globe to Buenos Aires, Hong Kong, Paris, Rome, and beyond, offering consultations to cities afflicted by relentless rat populations. Television documentaries, movie directors, major newspapers, magazines by the dozen, university recognition, and much more, Corrigan is lauded for an encyclopedic grasp of rats. Yet, the affable Corrigan, 65, is far removed from the ivory tower of academia. When he’s not on a rat-lecture tour, he’s typically found with a flashlight crawling through the pitch-black of an abandoned building, crouching in a dim alley, or lowering a microphone into a burrow to record the incessant chatter of a rat colony.
In subways, sewers, basements, beneath subflooring, or below buildings, Corrigan enters the dark confines of rat-ruled domains that attack the physical senses and send nauseous chills up most spines, as musky, gamey odors emanate from layers of defecation, with the smells piggybacked by the rat colony’s unmistakable vocalizations slicing through the darkness. “It’s like all of your senses assaulted at one time,” Corrigan describes. “Once you go in their world, the odors are pungent, almost like a zoo in a tight space. You hear scurrying, audible communication, squeaks, and teeth chattering. You stand still and watch them dart, jump, and stand on back legs to box one another. There are lots of shrieks of pain because they’re always biting each other in dominance, attacking each other’s flanks and taking big bites out of other males.”
Twice in his career, Corrigan has been bitten—a pain of reckoning from an animal capable of six bites per second with jaws delivering a 7,000 lb. per square inch crunch. “I’ve had rats within a couple inches spit right at me,” he continues. “They’ll grunt and stomp their feet just like a buck in the woods.”
Corrigan has seen rats burrow beneath foundations and take out sidewalks, streets, retaining walls and even sewer systems. “If you have a grain bin with a slab footing, or any other farm building, they’ll burrow under in a blink and crack the slab. A major, major expense to fix.”
Despite burrowing hazards, the biggest threat, he says, is consistent gnawing damage. “Wherever you have wires, they’re going to chew and cause high dollar damage. Gas lines, water lines, vehicle wires, building wires—so much expense. Even for airplanes in agriculture, they’ll chew on those wires. It’s such a big deal and you never want to let rats live on your farm. Never take the complacent attitude that every farm has rats.”
All You Can Eat
Farm rats are divided into two types of the same species, black and brown. The black rat (roof rat) usually lives above ground, often building nests in trees or rafters, and is a steady blight on the citrus and orchard industries. The brown rat (Norway rat) is the grand burrower, at home in the sewers of New York City or beneath a Midwest dairy barn or in the side of a Mississippi Delta irrigation ditch. Brown rats arrived in the U.S. during the late 1700s, as stowaways on European ships, and then spread across the country, riding the coattails of human habitation. Find people, find brown rats.
Rodents make up nearly half (43%) of all mammals on Earth—an undeniably strong indicator of survival skills. And in the mammalian kingdom, brown rats have a spot at the head of the survival table. They can go from easy pickings in a livestock barn to scraping a living in bare rocks beside the ocean, swimming underwater when necessary to find food. Coal mines, mountains, or cities: Whatever pitch the planet throws, the rats hit.
Along with remarkable adaptation skills, brown rats possess a mind-boggling capacity for reproduction. “They will crank out offspring like you can’t believe,” Corrigan says. “A single female can produce a chain of 15,000 offspring in a single year. Doesn’t happen often, but it can, given the right circumstances.”
And what are those “right circumstances?” What element triggers massive breeding? Abundant food. Combined with easy access, surplus food allows rats to take energy spent foraging and transfer it to mating. Females can copulate hours after giving birth, ovulate once every four days, and produce litters throughout their entire lives. (Life span in the wild is about 7-10 months, although a rat without stress can live for several years.) “With ample food and average pressure, rats can start breeding at 8 weeks of age (roughly 12 weeks with limited food). That’s 10-12 pups with plenty of food, and 4-5 pups with less food. Under stress and without food, they’ll kill and eat their own young to maintain caloric needs. Again, plenty of food is key.”
Grain is nature’s premium food source for rats, and their favorite meal, but when possible, rats select for complete nutritional balance (fruit) and need protein intake. They attack birds and smaller mammals as a meat source, and often supplement with insects. Generally, an average brown rat requires 3 oz. of food and 1 oz. of water to keep it strong in the wild; approximately 55-100 calories every 24 hours.
And where can rats access a bounty of food? Cities and farms. “Take a feed mill, for example, or even a set of grain bins,” Corrigan describes. “If a farmer doesn’t clean up properly, or the mill isn’t kept tight, you’re guaranteed hundreds of rats. People in the situation often think it’s thousands of rats, but it usually doesn’t work like that.”
“Astonishingly Smart Animals”
As with a beaver or squirrel, a rat’s front incisors never stop growing and are kept in check by incessant chiseling against the opposing pair. Whether electrical wire damage in equipment or buildings, most agriculture operations are frequent victims of rat teeth. Corrigan frequently places microphones inside burrows, and the noise from grinding or chattering teeth is a constant. “They can keep their own teeth filed down and don’t need to gnaw—that part is a myth. But we all know they do gnaw on anything and everything, and nobody is certain, but we think it’s because they are looking for reaction. Gnaw on bark searching for a cavity; gnaw on a stem and water drips out; gnaw on plastic or rubber and see what’s inside. Gnawing is exploring and hoping for something beyond or beneath.”
The blunt-muzzled brown rat is usually 12”-18” in length, and averages roughly 16 oz. in weight. Yet, particularly around farms, how does a creature that sometimes can grow to almost a pound-and-a-half move with incredible dexterity through tiny access holes? It’s all about the head.
“Once the head goes through, the body follows suit. I tell farmers, any hole where a quarter fits, or even less, is a rat door and needs repair because rats’ rib cages operate like hinges; they’re compressible. Shave a rat of its fur and you’ll be stunned by a scrawny mammal. Measure from the top of skull to bottom of the skull, and it’s half an inch and almost the same on side,” Corrigan notes.
Physically, rats are top athletes in the animal kingdom, capable of scaling rough surfaces, including the sides of brick buildings, or moving with a gymnast’s ease between pipes and rungs. “Watch them in a barn and you see unbelievable agility,” Corrigan describes. “This is a creature that can swim 72 hours without fail, or hold’s it breath several minutes underwater, swim up or down into/out of a toilet bowl, or dive in a creek for crawdads.”
(For related, see Rat Hunting with the Dogs of War, Farming's Greatest Show on Legs)
Riding shotgun alongside its adaptive qualities, breeding capacity, physical characteristics, and all-you-can-eat buffet diet, is a phenomenally high level of intelligence. The popular image of rats as dull and reactionary is false.
“Astonishingly smart animals,” Corrigan says, “We’ve been wrong in thinking every behavior we observed in rats was instinct. Measuring brain activity shows they experience a range of emotions and make calculations ahead of time, and make decisions based on previous experiences. The research is incredible and shows high intelligence—so high that it contains many of the capabilities we thought were reserved just for us and primates.”
“For example, let’s say a piece of food gets stuck between two barn doors. A rat will forage for a stick, and then use the stick as a tool to extract the food. That is game-changer intellect, and presents farmers with a question they might not want to hear, but it’s absolutely true: How do you control an animal with that level of intelligence? When it comes to rats, nothing is as simple as it first appears.”
“Rats are by no means stupid varmints. If you’ve got a rat problem on your property, then you’d better treat it carefully and with best management practices, just as you would with any type of livestock.”
Baptism By Fire
As a teenager growing up in Long Island, N.Y., Corrigan was the classic nature nerd, and after high school, he answered an advertisement for extermination work in an attempt to save money for college. It was baptism by fire: Corrigan was thrown into the sewers of New York City—the world’s emblematic hot zone of brown rat infestations.
The exterminator stint was followed by several years at Purdue University, where he cut his rat teeth in agriculture. Literally, Corrigan got on staff at Purdue and began rat research on Indiana farms and feed mills. (He still owns a small farm in Wayne County, and splits time between Indiana and New York.)
Corrigan, director of RMC Pest Management Consulting, is consistently bombarded with the same questions: How many rats live in the five boroughs of New York City? A trip through Google reveals a wild variation of purportedly concrete rat population totals—all false, Corrigan explains. “They’re just guessing, but they don’t want to say that. We don’t know a hard number, but it’s likely in the millions. One thing for sure, I suspect the cost of control is in the hundreds of millions of dollars each year. A great indicator of our rat population is the $4-$5 million in rat-related cleaning fines the city levies to people each year. Think about that: Almost $5 million in fines because of brown rats.”
Numbers, however, can be deceiving according to city size, and far more significant than population, Corrigan notes, is per capita presence. “Let’s say, just for argument, that New York City has 3 million rats, but much smaller Washington, D.C. has 500,000 rats. Who has the worse problem?”
The Rat War
Excluding the polar regions, the globe is a rat haven. There is only one mainland holdout—the ever-vigilant Canadian province of Alberta, which has…so far…won the rat race. Slightly larger in land mass than France, Alberta has kept brown rats at bay for 70 years, since the first recorded incident in 1950, when inspectors found rats on a farm in the southeast part of the province, along the Saskatchewan border. Government officials went into nuclear mode, sending armed men to the area to exterminate any and all rats, along with a publicity campaign including posters, pamphlets, free poison and public meetings on how to kill rats.
Bottom line: The effort paid off in spades, and as of 2020, Alberta has no resident or breeding population of brown rats. An eight-man rat patrol continues to monitor the border, and checks thousands of farms every year. In addition, Alberta maintains a rat hotline (310-RATS) and keeps rat prevention in the public eye.
However, take Alberta’s story off the table, along with rat elimination success on a few islands, and it’s readily apparent that rat races seldom end with human victories.
The Warhorses
Film producers consistently badger Corrigan for a money shot—thousands of rats in one place, existing as a camera-ready hoard. Such a location, Corrigan insists, is pure fiction. Rats are highly gregarious, but as multiple families form colonies, the rats migrate into new territory, shifting in search of balanced food opportunity. “You can end up with 400-500 rats on a single acre, but when it gets that bad, they move down the road or follow the creek to the next property. Your rat becomes your neighbor’s rat.”
However, Corrigan has seen exceptions. “Again, it’s all about food. I’ve been on some mismanaged swine operations where there were thousands of rats in one location, but those types of situations are not the norm.”
Below ground, or deep in the bowels of a city or farm structure, rats live in family units, typically sleeping in basketball-sized nests, Corrigan describes. “I’ve opened a nest and seen 30 rats explode in all directions. Especially in winter, they’ll all hugger-mugger together for body heat, but if food is in short supply, they’ll stay separate and get extremely aggressive.”
Aggression is standard in the rat world and dominant males are a force, Corrigan insists. “They’re truly tough looking, almost like an old warhorse, and packed with bulk, muscle, and a ‘Don’t mess with me,’ attitude. The biggest rat on a farm totally runs the show.”
Despite near-mythic status, king rats are fiction, he insists. “I’ve personally never seen anything confirmed in a brown rat over 1 lb. and 6 oz. Lots of guys tell me they’ve seen rats the size of cats. No, you saw a cat.”
Deputy Dog
Tucked deep in the Mississippi Delta, 1,200 miles from New York City, Mike Wagner’s Two Brooks Farm is an exceptional rice and soybean outfit focused on crop quality and conservation. Wagner’s farming operation is unique; his rat problem is not.
In the winter of 2018, he bought an old, low-dollar combine, exclusively for cutting test plots, and prior to the 2019 harvest, was forced to rewire the machine due to depredation from rats. Rice and rats are an unholy pair, and although Wagner experienced an onslaught of rodent damage, he managed to find a unique solution.
Rats were a financial drain on his Tallahatchie County grain bin system, often inflicting $10,000 to $20,000 in damage per year. On a whim, Wagner brought in a six cats to his farming headquarters, hoping to stem the bin damage—and clockwork, the rat problem ceased. “It was amazing, but it only worked for a short time—then the coyotes showed up and killed the cats at night.”
Cats killed the rats; coyotes killed the cats; the rats returned. Once again, Wagner relied on Mother Nature, adopting an abandoned Great Pyrenees dog to protect a second batch of cats. The new dog, Deputy, flipped the balance back in Wagner’s favor. Afraid of Deputy, the coyotes stayed on the perimeter, and the cats were free to prey on rats. Wagner’s old-school solution, through the soldiering of a Great Pyrenees, won the day—and still keeps the rats at bay around the bins. “That special dog was the end of my trouble,” Wagner says.
Plain Truth
Rat control on a farm (or in a city environment) is packed with irony, because the best control is obvious, yet seldom practiced: Cut off the food supply. If a family unit of 16 rats consumes just a pound of food per night, multiplied by seven each week, and extrapolated to 30 lb. of intake per month, how can a farmer, surrounded by augers, bins and livestock, stop the flow? “There is no magic wand. Nobody can clean or secure everything,” Corrigan says, “but you can have an immediate impact on whether you have 50 or 500 rats. Keep your rat population at 50 and then you can have a shot at them with rodenticides and rat traps.”
In an urban location, brown rats will forage up to 500’ from their nests, but typically stay within 100’, provided a food source exists. In a farming environment, proximity is much narrower, and forage distances significantly shrink. “The No. 1 concern is to shut off food sources, but you’d be amazed by how few people do that,” Corrigan explains. “Don’t go the hardware store, buy poison, and put it out at random. We can all fix a leaking pipe, but to what degree? The secret to poison is proper location where the rats truly are, otherwise it’s ineffectual, costs a ton of money, and may hurt other animals.”
Despite the destructive power of rats, Corrigan maintains tremendous respect for a species geared to survive. “What’s not to admire about a species specializing in success? There is still a ton of mystery surrounding rats and the more we learn, the better off we can control them in cities and in agriculture.”
“The truth is plain about rats in farming,” Corrigan adds. “If you don’t clean up spilled grain and leaking augers, and if you don’t cut off the main food sources, then you’re going to have huge rat problems that poison and traps won’t fix. You can’t bail out an ocean.”
For more, see:
Rat Hunting with the Dogs of War, Farming's Greatest Show on Legs
Misfit Tractors a Money Saver for Arkansas Farmer
Predator Tractor Unleashed on Farmland by Ag's True Maverick
Government Cameras Hidden on Private Property? Welcome to Open Fields
Farmland Detective Finds Youngest Civil War Soldier’s Grave?
Descent Into Hell: Farmer Escapes Corn Tomb Death
Evil Grain: The Wild Tale of History’s Biggest Crop Insurance Scam
A Skeptical Farmer's Monster Message on Profitability
Farmer Refuses to Roll, Rips Lid Off IRS Behavior
Killing Hogzilla: Hunting a Monster Wild Pig
Shattered Taboo: Death of a Farm and Resurrection of a Farmer
Frozen Dinosaur: Farmer Finds Huge Alligator Snapping Turtle Under Ice
Breaking Bad: Chasing the Wildest Con Artist in Farming History
In the Blood: Hunting Deer Antlers with a Legendary Shed Whisperer
Corn Maverick: Cracking the Mystery of 60-Inch Rows
Blood And Dirt: A Farmer's 30-Year Fight With The Feds
