The Long Read: Rats spread disease, decimate crops and very occasionally eat people alive. For centuries, we have struggled to find an effective way of controlling their numbers. Until now
First, the myths. There are no super rats. Apart from a specific subtropical breed, they do not get much bigger than 20 inches long, including the tail. They are not blind, nor are they afraid of cats. They do not carry rabies. They do not, as was reported in 1969 regarding an island in Indonesia, fall from the sky. Their communities are not led by elusive, giant king rats. Rat skeletons cannot liquefy and reconstitute at will. (For some otherwise rational people, this is a genuine concern.) They are not indestructible, and there are not as many of them as we think. The one-rat-per-human in New York City estimate is pure fiction. Consider this the good news.
In most other respects, the rat problem, as it has come to be known, is a perfect nightmare. Wherever humans go, rats follow, forming shadow cities under our metropolises and hollows beneath our farmlands. They thrive in our squalor, making homes of our sewers, abandoned alleys, and neglected parks. They poison food, bite babies, undermine buildings, spread disease, decimate crop yields, and very occasionally eat people alive.A male and female left to their own devices for one year the average lifespan of a city rat can beget 15,000 descendants.
There may be no king rat, but there are rat kings, groups of up to 30 rats whose tails have knotted together to form one giant, swirling mass. Rats may be unable to liquefy their bones to slide under doors, but they dont need to: their skeletons are so flexible that they can squeeze their way through any hole or crack wider than half an inch. They are cannibals, and they sometimes laugh (sort of) especially when tickled. They can appear en masse, as if from nowhere, moving as fast as seven feet per second. They do not carry rabies, but a 2014 study from Columbia University found that the average New York City subway rat carried 18 viruses previously unknown to science, along with dozens of familiar, dangerous pathogens, such as C difficile and hepatitis C. As recently as 1994 there was a major recurrence of bubonic plague in India, an unpleasant flashback to the 14th century, when that rat-borne illness killed 25 million people in five years. Collectively, rats are responsible for more human death than any other mammal on earth.
Humans have a peculiar talent for exterminating other species. In the case of rats, we have been pursuing their total demise for centuries. We have invented elaborate, gruesome traps. We have trained dogs, ferrets, and cats to kill them. We have invented ultrasonic machines to drive them away with high-pitched noise. (Those machines, still popular, do not work.) We have poisoned them in their millions. In 1930, faced with a rat infestation on Rikers Island, New York City officials flushed the area with mustard gas. In the late 1940s, scientists developed anticoagulants to treat thrombosis in humans, and some years later supertoxic versions of the drugs were developed in order to kill rats by making them bleed to death from the inside after a single dose. Cityscapes and farmlands were drenched with thousands of tons of these chemicals. During the 1970s, we used DDT. These days, rat poison is not just sown in the earth by the truckload, it is rained from helicopters that track the rats with radar in 2011 80 metric tonnes of poison-laced bait were dumped on to Henderson Island, home to one of the last untouched coral reefs in the South Pacific. In 2010, Chicago officials went natural: figuring a natural predator might track and kill rats, they released 60 coyotes wearing radio collars on to the city streets.
Still, here they are. According to Bobby Corrigan, the worlds leading expert on rodent control, many of the worlds great cities remain totally overcome. In New York were losing that war in a big way, he told me. Combat metaphors have become a central feature of rat conversation among pest control professionals. In Robert Sullivans 2014 book Rats, he described humanitys relationship with the species as an unending and brutish war, a battle we seem always, always to lose.
Why? How is it that we can send robots to Mars, build the internet, keep alive infants born so early that their skin isnt even fully made and yet remain unable to keep rats from threatening our food supplies, biting our babies, and appearing in our toilet bowls?
Frankly, rodents are the most successful species, Loretta Mayer told me recently. After the next holocaust, rats and Twinkies will be the only things left. Mayer is a biologist, and she contends that the rat problem is actually a human problem, a result of our foolish choices and failures of imagination. In 2007, she co-founded SenesTech, a biotech startup that offers the promise of an armistice in a conflict that has lasted thousands of years. The concept is simple: rat birth control
The rats primary survival skill, as a species, is its unnerving rate of reproduction. Female rats ovulate every four days, copulate dozens of times a day and remain fertile until they die. (Like humans, they have sex for pleasure as well as for procreation.) This is how you go from two to 15,000 in a single year. When poison or traps thin out a population, they mate faster until their numbers regenerate. Conversely, if you can keep them from mating, colonies collapse in weeks and do not rebound.
Solving the rat problem by putting them on the pill sounds ridiculous. Until recently no pharmaceutical product existed that could make rats infertile, and even if it had, there was still the question of how it could be administered. But if such a thing were to work, the impact could be historic. Rats would die off without the need for poison, radar or coyotes.
SenesTech, which is based in Flagstaff, Arizona, claims to have created a liquid that will do exactly that. In tests conducted in Indonesian rice fields, South Carolina pig farms, the suburbs of Boston and the New York City subway, the product, called ContraPest, caused a drop in rat populations of roughly 40% in 12 weeks. This autumn, for the first time, the company is making ContraPest available to commercial markets in the US and Europe. The team at SenesTech believes it could be the first meaningful advance in the fight against rats in a hundred years, and the first viable alternative to poison. Mayer was blunt about the implications: This will change the world.
Mayer is a tall, vigorous woman in her mid-60s with bright eyes, spiky grey hair and a toothy grin. Her ideologies of choice are Buddhism and the Girl Scouts. Its kind of my core, she said of the latter, to do for others. In conversation, her manner is so upbeat that she seems to be holding forth radiantly before an audience or on the verge of bursting into song. When asked how she is doing, she frequently responds in a near-rapture: If I was any better, Id be a twin! she also appears to enjoy watching people wonder whether this is an expression they should know.
When I took a seat in her office earlier this year, she clapped her hands triumphantly and said Ooh! Youre sitting in history and strength! There was a pause. I had a feng shui person come and do my office, she explained.