6 myths about rats, one of the most widespread creatures on Earth
‘We know more about life on Mars than how rats navigate life on Earth,’ researcher says
The brown rat (Rattus norvegicus) is one of the most ubiquitous and familiar creatures on the planet — but also perhaps one of the least understood.
According to Kaylee Byers, one of the lead researchers with the Vancouver Rat Project, "In some ways, we know more about life on Mars than how rats navigate life on Earth."
"Rats have long been associated with filth, disease and death," said Bobby Corrigan, a world-renowned rodentologist and New York City's unofficial "rat czar."
In Rat City, a documentary from The Nature of Things, Corrigan and Byers lead viewers down the rathole through the secret world of the brown rat, celebrating these heroes of evolution and dispelling a plethora of tall tales.
"If you consider their mysterious lifestyle and most people's visceral fear of [them]," said Corrigan, "it's no surprise that a whole slew of fantastic myths and urban legends have arisen through the ages about our shadowy partners in civilization."
Many of the horror stories we hear about rats don't hold water. Here are six myths about the rodents, ripe for debunking.
Myth: Rats were responsible for the Black Death
It's a common belief that the Black Death spread through parts of the world partly thanks to rats (and their fleas) climbing aboard ships and infecting people in distant lands.
The plague is caused by Yersinia pestis, a bacterium with a 30 to 100 per cent mortality rate, if left untreated. Now, scientists believe it was more likely body lice and human fleas, not rats, that were the real culprits of the 14th century pandemic and subsequent outbreaks. They believe the plague spread too quickly for rats to be the driver.
In testing three models of transmission, the rat model didn't match the speed at which the disease spread.
"It would be unlikely to spread as fast as it did if it was transmitted by rats," Nils Stenseth, a co-author of the study, told BBC News. "It would have to go through this extra loop of the rats, rather than being spread from person to person."
Myth: Rats are common carriers of rabies
If you're bitten by a bat, fox, raccoon or even a cat or dog, you're usually treated for rabies after as a precaution. Not so in the case of a rat bite, said Corrigan. The brown rat is unlikely to transmit the rabies virus in North America.
Rats are more likely to transmit other pathogens like salmonella, E. coli and the potentially deadly disease rat-bite fever, but it all depends on where the rat lives.
That's because rats are serious homebodies, only venturing about 100 metres from their nest in search of food or water. So the particular diseases carried by rats vary by city block, according to Byers.
In her studies, 60 per cent of rats on one block might carry Leptospira, a pathogen spread through their urine. But there might be no trace at all in the rats that live across the street. Your risk is all about your neighborhood rats.
Myth: Rats are only attracted to run-down neighbourhoods
Wrong! Rats live everywhere.
We tend to associate rats with the lower-income areas of cities. Deteriorating and poorly maintained buildings are often filled with cracks and crevices that allow rats to move in and out, and they may have more access to our garbage due to illegal dumping or improper disposal.
But rats are opportunistic creatures. If they have shelter and access to food and water nearby, they are happy to make themselves at home anywhere, whether it's in an abandoned building or a deluxe high-rise apartment.
Myth: Rats can grow as big as cats
In 2015, a photo supposedly of a 19-kilogram super rat caught in New York City made the rounds. It's not the first time "rodents of unusual size" (for those familiar with The Princess Bride) have been rumoured to scurry among us, but the truth is that monstrous city rats are fiction. It's possible the image was of a large pet rat photographed with forced perspective.
A typical brown rat is 40 centimetres long, including its tail, and maxes out at 500 grams. "The average rat is not anything of great size," Corrigan said in an interview.
So all those tales of ginormous rats? There's no such thing, according to Corrigan. "If anyone ever brings me a two-pound Norway rat, I will write them a cheque for $500," he said. "It's never gonna happen!"
Myth: Rats can chew through steel
Rats' sharp incisors never stop growing. As rodents, their teeth are key to their success, allowing them to gnaw through all manner of materials — just not stainless steel.
Their chompers are attached to strong jaw muscles and their chisel-like teeth can gnaw away at many materials, like wood, vinyl, plastic, drywall and even brick and aluminum if it's worth their effort.
To keep their relentlessly growing teeth sharp and trimmed, rats don't have to gnaw on hard objects, but can simply grind their top and bottom incisors together, maintaining a razor-sharp tool that comes in very handy.
Myth: We'll soon be overrun with rats!
Some fear the milder winters resulting from climate change could cause rat populations to explode, making it impossible to keep them in check. Given that a single female brown rat has the capacity to produce 15,000 descendents in a single year, it's a scary thought!
But before you scream in anguish, be reassured: it's unlikely we'll be overrun.
While Corrigan said mild winters may allow for one additional litter annually, many factors contribute to fluctuations in urban rodent populations.
According to him, increased construction, poor waste management, dense neighbourhoods, urban sprawl and aging infrastructure all play a role in how well rats fare in our cities.
In fact, human behaviour contributes more to infestations than rats do. Rats are opportunists and are often just taking advantage of our litter problem.
"If humans would get organized on their rat management programs, allocate the right amount of monies and resources toward rat abatement, and each and every person treat his or her urban environment with a commitment to 'leaving it cleaner than you found it,' we could perhaps put Rattus norvegicus on the 'rarely seen' list of urban wildlife," Corrigan wrote in an online post.
Watch Rat City on The Nature of Things.
Jeff Morales is the director of Rat City.
