by Bill Bryson
Mostly, however, rats are just immensely lazy. They spend up to twenty hours a day asleep, normally emerging to look for food just after sunset. They seldom venture more than 150 feet if they can possibly help it. This may be part of a survival policy, for mortality rates rocket whenever they are compelled to migrate.
When rats are mentioned in a historical context, the one topic that invariably follows is plague. This may be not quite fair. For one thing, rats don’t actually infect us with plague. Rather, they harbor the fleas (that harbor the bacteria) that spread the disease. Plague kills rats just as energetically as it kills us. Indeed, it kills many other things, too. One of the signs of a plague outbreak is lots of dead dogs, cats, cows, and other animals scattered about. Fleas much prefer the blood of furry creatures to the blood of humans, and generally turn to us only when nothing better is available. For that reason, modern epidemiologists in places where plague is still common—notably parts of Africa and Asia—generally avoid culling rats and other rodents too enthusiastically during outbreaks. In a very real sense there is no more welcome time for rats to be around than when plague is rampant. Anyway, more than seventy other creatures besides rats—including rabbits, voles, marmots, squirrels, and mice—have been implicated in the spread of plague. Moreover, possibly the very worst plague outbreak in history doesn’t seem to have involved rats at all, at least not in England. Long before the notorious Black Death of the fourteenth century, an even more ferocious plague devastated Europe in the seventh century. In some places almost everyone died. The Venerable Bede, in his history of England written in the following century, says that when the pestilence reached his monastery at Jarrow, it killed everyone except the abbot and one boy—a mortality rate considerably over 90 percent. Whatever was the source of its spread, it wasn’t rats, it seems. No rat bones from the seventh century have been found anywhere in Britain—and people have looked hard. One excavation in Southampton collected fifty thousand animal bones from in and around a cluster of dwellings; none came from a rat.
It has been suggested that some outbreaks attributed to plague may not have been plague at all, but ergotism, a fungal disease of grain. Plague didn’t come at all to many cold, dry northern places—Iceland escaped entirely, as did much of Norway, Sweden, and Finland—even though those places had rats. At the same time, plague was associated with miserably wet years almost everywhere it appeared—the very circumstances that would tend to produce ergotism. The one problem with the theory is that the symptoms of ergotism are not much like those of plague. It may be that the word pestilence was used loosely or vaguely and simply misinterpreted by later historians.
Even just a generation or two ago, rat numbers in urban areas may have been considerably higher than now. The New Yorker reported in 1944 that a team of exterminators working in a well-known (but carefully unidentified) hotel in Manhattan caught 236 rats in the basement and subbasement in three nights. At about the same time, rats all but took over the aforementioned Gansevoort poultry market. They invaded in such numbers that secretaries sometimes found rats leaping out of their desk when the drawers were opened. Exterminators were called in and caught four thousand rats in a matter of days, but they couldn’t make the market ratproof. In the end it was shut down.
It is commonly written that there is one rat for every human being in a typical city, but studies have shown that to be an exaggeration. The actual figure is more like one rat for every three dozen people. Unfortunately, that still adds up to a lot of rats—a quarter of a million in New York City, for instance.
II
The real life in your house is at a much smaller scale. Down at the realm of the very tiny, your house teems with life: it is a veritable rain forest for crawling, clambering things. Armies of tiny creatures patrol the boundless jungles of your carpet fibers, paraglide amid floating motes of dust, crawl across the bedsheets at night to graze on the vast, delicious, gently heaving mountain of slumbering flesh that is you. These creatures exist in numbers you cannot comfortably imagine. Your bed alone, if it is averagely clean, averagely old, averagely dimensioned, and turned averagely often (which is to say almost never) is likely to be home to some two million tiny bed mites, too small to be seen with the naked eye but unquestionably there. It has been calculated that if your pillow is six years old (which is the average age for a pillow), one-tenth of its weight will be made up of sloughed skin, living and dead mites, and mite dung—or frass, as it is known to entomologists.
Clambering among the bed mites, on a much more gigantic scale, might also these days be lice, for it appears that these creatures, once nearly vanquished, are making a comeback. Like rats, lice come in two principal varieties: Pediculus capitas, or head lice, and Pediculus corporis, or body lice. These latter (familiarly known as cooties, probably from the Malay term kutu) are relative newcomers on the bodily irritants scene. They evolved sometime in the last fifty thousand years from head lice. Of the two, head lice are much smaller (they are about the size of a sesame seed, and actually look much the same) and so harder to detect. An adult female head louse will lay three to six eggs per day. Each louse can live for about thirty days. Lice eggs are called nits. Lice have developed an increasing resistance to pesticides, but the greatest reason for their increase, it seems, is low-temperature wash cycles in washing machines. As Dr. John Maunder of the British Medical Entomology Centre has put it: “If you wash lousy clothing at low temperatures, all you get is cleaner lice.”
Historically, the most common bedroom dread was bedbugs—Cimex lectularius, as the little blood suckers are scientifically known. Bedbugs made sure that no one ever slept alone. In former times, people were driven half mad by bugs and the desire to be rid of them. When Jane Carlyle discovered that bedbugs had invaded her housekeeper’s bed, she had the bed taken to pieces and carried to the garden, where each piece was washed with chloride of lime, then immersed in water for two days to drown any bugs that survived the disinfectant. The bedding meanwhile was taken to a sealed room and dusted repeatedly with disinfectant powder until no more bugs emerged. Only then was it put back together and the housekeeper allowed to resume a normal night’s sleep, in a bed that was now almost certainly at least mildly toxic to her as well as to any insect life that dared to creep back in.
Even when beds weren’t actively infested, it was routine to take them apart at least once a year and paint them with disinfectant or varnish as a precaution. Manufacturers often advertised how quickly and easily their beds could be dismantled for an annual maintenance. Brass beds became popular in the nineteenth century not because brass was suddenly thought a stylish metal for bedsteads, but because it gave no harbor to bedbugs.
Like lice, bedbugs are making an unwelcome comeback. For most of the twentieth century they were virtually extinct in most of Europe and America thanks to the rise of modern insecticides, but in recent years they have been vigorously rebounding. No one is sure why. It may have something to do with more international travel—people bringing them home in their suitcases and so on—or that they are developing greater resistance to the things we spray at them. Whatever it is, they are suddenly being noticed again. “Some of the best hotels in New York have them,” the New York Times quoted one expert as saying in a report in 2005. The Times article went on to note that because most people have no experience of bedbugs and don’t know what to look out for, they are likely to discover they are infested only when they wake up and find themselves lying in a swarm of them.
If you had the right equipment and a peculiar measure of motivation, you could find numberless millions of dinky creatures living with you—vast tribes of isopods, pleopods, endopodites, myriapods, chilopods, pauropods, and other all-but-invisible specks. Some of these little creatures are practically ineradicable. An insect named Niptus hololeucus has been found living in cayenne pepper and in the cork stoppers of cyanide bottles. Some, like flour mites and cheese mites, dine with you pretty regularly.
Move down to the next level of living
things, to the world of microbes, and the numbers swell beyond counting. Your skin alone is home to about a trillion bacteria. Inside you are many thousands of trillions more, many of them engaged in necessary and helpful tasks like breaking down food in the gut. Altogether you hold about a hundred quadrillion bacterial cells in your body. If you took them out and put them in a pile, they would weigh about four pounds. Microbes are so ubiquitous that we easily forget that a large part of every modern house is taken up with heavy metal objects—refrigerators, dishwashers, washing machines—that exist exclusively to kill or suppress them. Getting germs out of our lives is a kind of endless daily quest for most of us.
The most celebrated germ expert in the world is almost certainly Dr. Charles P. Gerba of the University of Arizona, who is so devoted to the field that he gave one of his children the middle name Escherichia, after the bacterium Escherichia coli. Dr. Gerba established some years ago that household germs are not always most numerous where you would expect them to be. In one famous survey he measured bacterial content in different rooms in various houses and found that typically the cleanest surface of all in the average house was the toilet seat. That is because it is wiped down with disinfectant more often than any other surface. By contrast the average desktop has five times more bacteria living on it than the average toilet seat.
The dirtiest area of all was the kitchen sink, closely followed by the kitchen counter, and the filthiest object was the kitchen washcloth. Most kitchen cloths are drenched in bacteria, and using them to wipe counters (or plates or breadboards or greasy chins or any other surface) merely transfers microbes from one place to another, affording them new chances to breed and proliferate. The second most efficient way of spreading germs, Gerba found, is to flush a toilet with the lid up. That spews billions of microbes into the air. Many stay in the air, floating like tiny soap bubbles, waiting to be inhaled, for up to two hours; others settle on things like your toothbrush. That is, of course, yet another good reason for putting the lid down.
Almost certainly the most memorable finding of recent years with respect to microbes was when an enterprising middle school student in Florida compared the quality of water in the toilets at her local fast-food restaurants with the quality of the ice in the soft drinks, and found that in 70 percent of outlets she surveyed the toilet water was cleaner than the ice.
What is perhaps most remarkable about all these multitudinous life forms is how little we sometimes know about them—and how recently what we do know has been learned. Bed mites weren’t discovered at all until 1965, even though millions of them exist in every bed. As late as 1947, a medical correspondent for The New Yorker could write: “Mites are only infrequently found in this country and until recently were practically unknown in New York City.” Then, in the late 1940s, residents of an apartment complex called Kew Gardens in Queens, New York, began sickening in large numbers with flulike symptoms. The malady was known as “the Kew Gardens mystery fever” until an astute exterminator noticed that mice were also getting sick and discovered on close inspection that tiny mites living in their fur—the very mites that were supposed not to exist in America in large numbers—were transmitting rickettsialpox, a kind of spotted fever, to apartment dwellers.
Similar degrees of ignorance have long applied to many larger creatures, not least one of the most important and least understood of all animals that are sometimes found in modern houses: bats. Hardly anybody likes bats, which is truly unfortunate because bats do much more good than harm. They eat enormous quantities of insects, to the benefit of crops and people alike. Brown bats, the most common species in America, consume up to six hundred mosquitoes per hour. Tiny pipistrelle bats—which weigh no more than a small coin—vacuum up three thousand insects apiece in the course of a night’s swoopings. Without bats there would be a lot more midges in Scotland, chiggers in North America, and fevers in the tropics. Forest trees would be chewed to pieces. Crops would need more pesticides. The natural world would become a very stressed place. Bats are also vital to the life cycles of many wild plants through pollination and seed dispersal. A seba bat—a tiny bat in South America—will eat as many as sixty thousand tiny seeds per night. The seed distribution of a single colony of seba bats—about four hundred bats—can produce nine million seedlings of new fruit trees a year. Without the bats, those fruit trees wouldn’t happen. Bats are also critical to the survival in the wild of avocados, balsa, bananas, breadfruit, cashews, cloves, dates, figs, guavas, mangoes, peaches, and saguaro cactus, among others.
The world has far more bats than most people realize. In fact, about a quarter of all mammal species—some eleven hundred in all—are bats. They range in size from tiny bumblebee bats, which really are no bigger than bumblebees and therefore are the smallest of all mammals, up to the magnificent flying foxes of Australia and south Asia, which can have wingspans of six feet.
At times in the past attempts have been made to capitalize on bats’ special qualities. In the Second World War, the American military invested a great deal of time and money in an extraordinary plan to arm bats with tiny incendiary bombs and to release them in vast numbers—as many as a million at a time—from planes over Japan. The idea was that the bats would roost in eaves and roof spaces, and that soon afterward tiny detonators on timers would go off and they would burst into flames, causing hundreds of thousands of fires.
Creating sufficiently tiny bombs and timers required a great deal of experiment and ingenuity, but finally in the spring of 1943 work had progressed sufficiently that a trial was set to take place at Muroc Lake, California. It would be putting it mildly to say that matters didn’t go quite to plan. Remarkably for an experiment, the bats were fully armed with live bomblets when released. This proved not to be a good idea. The bats failed to light on any of the designated targets, but did destroy all the hangars and most of the storage buildings at the Muroc Lake airport, as well as an army general’s car. The general’s report on the day’s events must have made interesting reading. In any case, the program was canceled soon afterward.
A rather less harebrained, but ultimately no more successful, plan to make use of bats was conceived by a Dr. Charles A. R. Campbell of Tulane University Medical School. Campbell’s idea was to build giant “bat towers,” where bats would roost and breed, and then go out to eat mosquitoes. This, Campbell believed, would substantially reduce malaria and also provide guano in commercially worthwhile quantities. Several of the towers were built, and some actually still stand, if precariously, but they never worked. Bats, it turns out, don’t like to be told where to live.
In America, bats were persecuted by health officials for years because of inflated—and at times irrational—concerns that they carried rabies. The story began in October 1951 when an anonymous woman in west Texas, the wife of a cotton planter, came across a bat in the road outside her house. She thought it was dead, but when she bent to look at it, it leaped up and bit her on the arm. This was highly unusual. American bats are all insectivores and none had ever been known to bite a human. She and her husband disinfected and dressed the wound—it was just a small wound—and didn’t think anything more of it. Three weeks later the woman was admitted to a hospital in Dallas in a delirious condition. She was “wildly agitated,” and unable to speak or swallow. Her eyes were filled with terror. She was beyond help. Rabies can be successfully treated, but only if the treatment is immediate. Once symptoms start, it’s too late. After four days of unutterable distress, the woman slipped into a coma and died.
Now scattered cases of people being bitten by rabid bats began to crop up in other locations—two in Pennsylvania; one each in Florida, Massachusetts, and California; two more in Texas. All this was over the space of four years, so it was hardly rampant, but it did cause concern. Finally, on New Year’s Day 1956, a public health official in Texas, Dr. George C. Menzies, entered a hospital in Austin with rabies symptoms. Menzies had been studying caves in central Texas for evidence of rabies-bearing bats, but hadn’t b
een bitten or otherwise exposed to rabies as far as anyone knew. Yet somehow he became infected, and after just two days’ care he died in the usual hideous manner, in discomfort and terror, his eyes like saucers.
The case was widely reported and resulted in a kind of vengeful hysteria. Officials at the highest levels concluded that extermination was an urgent and necessary step. Bats became the most friendless creatures in America. Years of steady persecution followed, and bat populations in many places suffered shocking depredations. In one case, the largest bat colony in the world, at Eagle Creek, Arizona, experienced a population fall from thirty million to three thousand in a matter of years.
Merlin D. Tuttle, America’s leading bat authority and founder of Bat Conservation International, a charity for bats, related a case, reported in The New Yorker in 1988, in which public health officials in Texas told a farmer that if he didn’t kill the bats in a cave on his land, he and his family and their livestock would be at grave risk of contracting rabies. At their instructions, the farmer filled the cave with kerosene and lit it. The conflagration killed about a quarter of a million bats. When Tuttle interviewed the farmer later, he asked him how long his family had owned the property. About a century, the farmer replied. And in all that time, Tuttle went on, had they ever been troubled by rabies? No, the farmer responded.