Feral Cities (30 page)

How big a role the black rat played in the Black Death is disputed. Some argue that the plague's rapid spread could only have happened if the disease was transmitted person-to-person rather than from flea bites.

What's not in doubt, however, is that black rats thrived in the cities of old. They are capable climbers and could easily scale the walls of timber buildings to nest in attics or thatched roofs, an ability that earned them yet another name: the roof rat.

But their reign has passed. As streets got cleaner and builders swapped timber for brick, the black rat found the city less inviting. The final straw was a challenger from the East.

Although it is called the Norway rat, the brown rat has nothing to do with the Nordic nation. That name dates back to the rats' arrival in England, which was blamed on Norwegian ships even though the rodent is believed to have originated in northern China.

When the brown rat reached Europe and North America in the 1700s, it set to work usurping the black rat from its urban strongholds. The brown rats had evolution on their side. They are both larger and more aggressive than black rats and, crucially, they are burrowing rather than tree-dwelling rodents. So while the black rats were contending with new architecture that made it harder to nest in roofs, the brown rats found an abundance of basements and sewers to live in.

By the end of the 1800s, the brown rat had taken control of most North American and European cities. In Britain, the black rat nearly vanished altogether, ending up a rare sight outside of dockyards. They still cling on in warmer cities such as Phoenix, where they have gained a foothold in the Arcadia neighborhood, but the black rat's urban glory days are long gone.

Regardless of what species roams our streets, rats have many qualities that make them well suited to urban life, and one of the most important is that they are sex mad. Rats are promiscuous lovers with raging libidos, and adults can have sex twenty times a day. They are bisexual too, often mounting rats of the same sex. And all this sex results in lots of babies.

Rat pregnancies last just twenty-one days, and each litter produces eight to ten pups. And with the kids hitting puberty after sixty days, it doesn't take long before they are getting it on too. As a result, a single pair of rats can have up to fifteen thousand descendants in a single year. So it's just as well less than 5 percent live long enough to reach their first birthday.

Rats are also wary creatures. They avoid open spaces, preferring to run along walls where there is less chance of being spotted by predators like hawks or people. They also don't like change, preferring to retread the same routes night after night. If they find unfamiliar food they might nibble it, but they won't scarf it down until they are confident it is safe to eat. Same goes for the traps we lay for them. Rats will steer clear of traps when they first appear
and tend to only pluck up the courage to investigate further when it has been sitting idle for a few days.

This combo of fearfulness and horniness makes them good at surviving in the city. The wariness makes them hard to exterminate, and even when they slip up it won't be long before a newborn pup replaces the unlucky individual.

Rats are expert cat burglars too. They can squeeze through gaps of just three-quarters of an inch in diameter and if a hole proves too small to get through they have the tools to make it bigger. The brown rat's sharp incisors are as hard as glass or a steel knife, so they are more than capable of chiseling their way through brick, mortar, and other materials if the need arises.

As London's chief sewer flusher, Rob Smith has seen the impact of their tunneling abilities many times. Rob has worked the sewers of the British capital for decades. He started his career by helping to build sewers more than forty years ago before switching over to maintaining them for the water company Thames Water.

There are plenty of sewers to maintain. London's eight million residents are served by thousands of miles of sewers that mix together modern drains, overwhelmed Victorian tunnels, and “lost” subterranean rivers that have long been buried beneath the streets.

Much of Rob's job involves getting rid of fatbergs, the stinking lumps of cold cooking fat, used wet wipes, cotton swabs, tampons, and other unsavory detritus that congeal in the sewers and block the tunnels. Every year Thames Water deals with forty thousand of these vile blockages.

The biggest fatberg to date was discovered in 2013 after nearby residents complained they couldn't flush their toilets. The fifteen-ton monstrosity took Rob and his team three weeks to blast apart with high-pressure jets of water.

Encounters with rats are par for the course when fighting fat-bergs, Rob tells me over the phone, mere days before he hung up his gumboots for good and entered retirement. “The one that sticks
in my mind was down through Leicester Square a few years ago. The fat was floating on top of the sewage and it was like the M1 for rats,” he says, referring the motorway that links London and Leeds. “There were quite a few rats down there because they eat the fat and everything, so they had food and a means for getting from one area to another without getting into the sewage because they would cross over the top of the fat.”

Rob decided to fix the fat problem by redirecting sewage from other parts of the network into the area for a weekend to flush it away. The following Monday morning Rob and his team headed into the sewers under Long Acre to see the results. “We went down and, in that particular sewer, the stairs are very much like you'd expect to see in a lighthouse or something: a spiral staircase, bricks, and Yorkstone slabs. Of course, all the rats had sought sanctuary in these side entrances and along the stairs. I think that was about the most rats I'd ever seen.”

Having seen plenty of rats in their time, Rob and his colleagues weren't bothered. “They eye you from a distance,” he says. “They will move out of the way and keep out of the light, so that you can just see their beady little eyes in the distance.

“There's three of us, sixteen or seventeen stone, quite big fellas with lights and making quite a lot of noise, and the rats start going down the stairs in front of us. Then they reached the point where they had no option but to go into the sewer and into the flow, and that's when they decided to come back up the stairs. So there was a bit of tap dancing going on, y'know.”

Despite being good swimmers, London's sewer rats do all they can to avoid entering fast-flowing sewer water, which is dangerous even for them. “Very often if you get a snap storm, you find quite a few of Roland Rat and his friends turn up down at the works because they drown,” says Rob, referring to the puppet that became a huge British children's TV star in the 1980s.

Fatbergs may be the problem that demands most of Rob's time, but the hard teeth of the rats mean they, too, threaten the city's
sewers. “Believe it or not, they gnaw their way through brickwork. They can make their own access points and ingress points,” he says. “A lot of the brick sewers rely on the ground around them to hold them in shape. So if you get rats digging around the outside of the sewer, it threatens the stability. In my twenty-odd years with Thames I've seen two or three points where rats have caused sewers, not to collapse, but to put the fabric of them at risk to the point that we've had to go down and do something about it.”

Although sewers are not the only place city rats live, life under our streets is idyllic if you're a rat, as a Danish study discovered. The researchers examined the lives of rats living in two neighboring but unconnected sewer systems in the Copenhagen suburb of Kongens Lyngby.

They found a rat society that was peaceful and content. Intruder rats that ventured into the sewers were rarely attacked by those already living there as would normally happen when a rat enters another's territory. The sewer-dwellers lived longer too, lasting four rather than three months on average, and the smaller, drier pipes served as ideal nurseries for rats to raise their young.

In fact, none of the rats tracked by the researchers ever left the sewer they were born in. They weren't interested in the surface world. They didn't venture into it, and their distribution through the system bore no relation to whether there were houses or stores above them.

But it's unlikely they went hungry because in the sewer the food never stops coming. “There's a hell of a lot of food that goes into the sewer system,” says Rob. “A lot of houses, especially the more upmarket places, and restaurants in London have got their disposal units. They just put the food in and it emulsifies it, and it goes out into the drainage system, and in places where you've got a fruit and veg market they hose it down and all the green stuff goes into the road gullies and then into sewers.”

Londoners often imagine that the rats living in the city's underworld favor the aging Victorian sewers, but that's not the case. Although the Victorian portion looms large in the imagination, when Thames Water funded a study to see if rat hotspots were linked to the age of the sewers, all the hotspots turned out to be in the post-Victorian parts of the network.

Actually, a lot of what we believe about city rats is wrong, not least the oft-repeated claim that there's one rat for every person in New York City or that you are never more than six feet away from a rat in London.

These dodgy statistics date back to a survey William Richard Boelter conducted for his 1909 book
The Rat Problem.
Boelter asked people living on farms around England whether it was reasonable to assume that there was one rat per acre. Everyone he asked said yes or that there would be more than that. He didn't even bother asking anyone living in villages, towns, or cities, because he assumed that one or more rats per acre was a given in urban areas.

Having concluded on this flimsy basis that there was indeed one rat per acre, he noted that there were forty million acres of land in the UK and, therefore, forty million rats. By coincidence the population of the UK was about forty million people at the time, spawning the claim that there was one rat for every person. It may have been a bogus figure, but it was attention-grabbing, so newspapers and pest controllers kept reciting it until it stuck, and somewhere along the way it morphed into the claim that you are never more than six feet away from a rat.

In truth rats are nowhere near that common, even in cities. A more recent and more methodical estimate by the UK government puts the country's rat population at ten and a half million, of which just one-third live in urban areas.

Even in New York City, where rats loom large in people's imagination, the one rat per person claim doesn't hold up. The city's most thorough rat census dates back to 1949, when researchers concluded that there were quarter of a million rats in the
five boroughs—well below the eight million Boelter's statistic suggested.

Although no one really knows how many rats live in the Big Apple today, even generous estimates based on reported rat sightings struggle to live up to the one-per-person claim. A crude estimate made by the news website
FiveThirtyEight
assumed that one in a hundred New Yorkers would report a rat when they saw one, that no rat would be seen twice, and that every sighting involved two rats. Apply that to the ten-thousand-odd sightings a year and that's two million rats in the city, one for every four people.

Equally surprisingly, city rats are less disease-ridden than their rural cousins. While it would go too far to call them clean, an Oxford University study comparing London rats with those from British farms found that country rats were dirtier.

The urban rats had lower levels of listeria, tapeworms, and roundworms. They were also less likely to have
Toxoplasma gondii.
This creepy protozan twists the brains of rats so they behave in ways that make them more likely to get eaten by cats, which are its final host, and it might be altering our minds too. About one in four people in the United States is infected with
T. gondii,
and it has been linked with increased risk of suicide and schizophrenia.

The rats were also free of the bacteria that cause the respiratory infection pseudomonas, which often thrives in hospitals. Even leptospirosis, the life-threatening disease rats are most associated with, was comparatively rare in the urban rodents. Only whipworms were more common in the city rats.

It seems that urban rats are less likely to get infected with these parasites because they have less contact with livestock excrement and, thanks to our own attention to hygiene, the rats living in the sewers are less exposed to parasites. As Rob tells me when I ask about the aroma of London's sewers: “It's not smelling of roses by any means, but it's not quite as bad as people think because they forget to factor into the equation the amount of water, soap, and scented perfume that gets washed into the sewer at the same time.”

Of course being cleaner than rural rats is hardly a recommendation, and with their potential to damage sewers, spread disease, and gnaw through electrical cables there are plenty of good reasons why cities seek to keep these rodents under control.