The Rat Studies that Foretold a Nightmarish Human Future

Rats can't vomit. This may be a function of their anatomy—their stomachs are "not well structured for moving contents towards the esophagus" is how one study delicately put it—or it may have something to do with their brain circuitry, or it may be a combination of the two. Whatever the cause, the result is that rats, contrary to their popular (or unpopular) image, are fussy eaters. Even as they pick through the trash, they're hesitant to try new foods. This makes poisoning them complicated; quite often—and quite literally—they won't take the bait.

In 1942, a Johns Hopkins biologist named Curt Richter discovered a new poison that rats apparently couldn't taste. His breakthrough caught the attention of the United States Office of Scientific Research and Development, the Second World War equivalent of DARPA. The agency, among its many worries, feared that the Axis powers were at work on biological weapons that would use rats as vectors. (In fact, the Japanese did try to spread plague during the war, with some success.) The O.S.R.D. had the poison—alpha-naphthyl thiourea, or ANTU for short—tested in the back alleys of Baltimore. The city was so pleased with the resulting carnage that it appointed Richter to lead a new rodent-control office, based in City Hall. By 1946, ANTU-laced corn had been spread over more than fifty-five hundred blocks and, according to Richter, "well over a million rats" had been killed.

By that point, however, ANTU was starting to lose its efficacy. Apparently, rats were learning to associate adulterated corn with unpleasant consequences and becoming bait-shy. New measures, it was realized, would be needed, and an even more ambitious research effort was born—the Rodent Ecology Project.

What We're Reading Discover notable new fiction and nonfiction.

The project was funded by the Rockefeller Foundation, which tapped another Johns Hopkins professor, David E. Davis, to lead it. Davis thought that the best way to control rats was to understand their habits. He set about studying how Baltimore's rats spent their days, or, really, nights, since the animals in question—Norway rats, which actually come from Asia—are nocturnal. He and his assistants trapped rats on the streets and marked them, usually by clipping off some of their toes. They released the digit-poor rodents back onto the streets, then tried to recapture them. In dry weather, they put out food infused with blue dye and tracked the tinted droppings that resulted.

These labor-intensive routines revealed that rats live in small groups of about fifteen individuals. They tend to stick close to home, and they don't like to cross roads. Davis's team also found that rat numbers were remarkably stable. About ten groups, or a hundred and fifty individuals, lived on an average block. If some of the rats on a block were killed, either by ANTU or by predators, the population quickly rebounded, levelling off again at about a hundred and fifty rats.

Such stability was hard to explain. Clearly, the rats' numbers were not limited by resources, as there was always more garbage to be plundered. So why didn't some blocks have a whole lot more rodent residents? One of Davis's assistants, a young ecologist named John B. Calhoun, suggested an experiment. What if additional rats were introduced on a street? Would the population increase? Calhoun trapped more than a hundred rats, marked them, and released them on one particular block. When he and his colleagues tried to recapture the imported rats, they couldn't find any. Meanwhile, it seemed, the block's original rat population had declined. As one account of the experiment put it, "It looked like the most effective rat killer was more rats."

Both Richter and Davis eventually moved on from the study of street rats to pursue other projects. But Calhoun was hooked. He would spend the rest of his life investigating what controlled rats' numbers, with results that many experts interpreted as ominous for humanity.

Two new books take up the subject of Calhoun and his rats. The authors of the first, "Rat City: Overcrowding and Urban Derangement in the Rodent Universes of John B. Calhoun" (Melville House), are a pair of British researchers, Edmund Ramsden and Jon Adams, who for a time both taught at the London School of Economics. The second, "Dr. Calhoun's Mousery: The Strange Tale of a Celebrated Scientist, a Rodent Dystopia, and the Future of Humanity" (University of Chicago), is by Lee Alan Dugatkin, a historian of science at the University of Louisville. Both books cast Calhoun as a visionary. Both also portray him as eccentric to the point of crankdom.

Calhoun, who went by the nickname Jack, was born in 1917 in rural Tennessee. His father was a school administrator and his mother a teacher. As a child, he was passionately interested in nature, particularly in birds. In 1933, his father lost his job, a development that might have prevented Calhoun from attending college, had ornithology not intervened. One day that summer, while visiting the University of Virginia, Calhoun ran into a dean who happened to be an avid birder. After just a few minutes of conversation, the dean offered him a scholarship to U.V.A. In 1943, Calhoun completed a Ph.D. at Northwestern University; a few years after that, he landed the position with the Rodent Ecology Project.

Calhoun's translocation experiment convinced him that there was still a lot to learn about the social lives of rats. But, he decided, he could no longer work on the streets of Baltimore; there were too many variables he couldn't control. Nor did it make sense to work with lab rats; their lives were too artificial. What he needed, Calhoun thought, was an urban setting only he had access to. With the blessing of the Rodent Ecology Project, he constructed a simulacrum of a city block on an empty lot in Towson, Maryland, about ten miles north of Baltimore. (Though it was smaller than an actual block, the setup replicated the typical layout of Baltimore's back yards and alleyways.) To keep the rats in and predators out, he erected an elaborate series of fences around his SimCity, and, to monitor the goings on there, he built himself a little observation tower. He placed ten wild rats—five males and five females—inside the fences, and then, for two years, he watched.

The Towson experiment produced reams and reams of data. Every six weeks, Calhoun would conduct a census of the enclosure's population by capturing every rat. (Individual rats were marked with metal ear tags.) Sometimes, before releasing the rats, he would anesthetize them so that he could record their size, their weight, and the number of their wounds. He tried to register every birth in the enclosure, and every death. In the process of all this, Ramsden and Adams write, Calhoun came to know "more about the behavior of the Norway rat than anyone else alive."

The Towson rats were supplied with essentially limitless food, and for a while they took advantage of this by increasing their numbers. At the end of a year, ten rats had become thirty. By the eighteen-month point, there were a hundred and fifty in the enclosure. Then the population abruptly levelled off. For the last six months of the experiment, it never rose above a hundred and eighty.

Having observed the rats so closely, Calhoun now had a pretty good idea of what was limiting growth. The rats had divided themselves into eleven clans. Four had burrows conveniently located at the center of the enclosure, near where Calhoun had placed the food bins. In these privileged clans, a few dominant male rats mated with (and protected) a larger number of females. Although the high-status mothers successfully raised many pups, this wasn't enough to offset the losses in a population that was aging and, increasingly, brawling.

The rats from the banlieues, for their part, lived under constant stress. When they attempted to get to the food bins, the fat rats in the middle tried—often successfully—to repulse them. Along the edges of the enclosure, packs of low-ranking males roamed from burrow to burrow, harassing the females. The outer-burrow females were so exhausted that they rarely conceived, and, when they did give birth, they often abandoned their pups.

Calhoun published his results in a two-hundred-and-eighty-eight-page monograph, "The Ecology and Sociology of Norway Rats." As Ramsden and Adams point out, the use of the word "sociology" in the title was daring, as this term is normally reserved for the study of humans. Toward the end of the volume, Calhoun made explicit his intention. "Animal subjects," he wrote, "may be of value in elucidating some of the social problems which confront man today."

Calhoun's Rodent Ecology Project contract ended in 1949. It took him almost a decade to get another major rat study up and running, but, when he did, it was an extravaganza. The new experiment was financed by the National Institute of Mental Health, which had just been created. At a cost of a hundred thousand dollars—more than a million dollars in today's money—Calhoun had a ten-foot-tall rat enclosure constructed in a barn in Gaithersburg, Maryland. The enclosure was divided into six rooms, each of which was further divided into four cells. This time around, Calhoun planned to control the enclosure's population himself, by removing pups when there were more than eighty rats per room.

The experiment got under way in January, 1958. For the first few months, the rats seemed content in their apartment-like dwellings. But then, once again, things took a dystopic turn. Calhoun had laid out the rooms asymmetrically. The two cells in the center each had two entrances; those on the ends had just one. Dominant males assumed control of the easier-to-defend cells and allowed only a select group of females to enter them. This forced the other rats into the central cells, where order gradually broke down. Dispensing with the courtship rituals that usually precede mating, mid-cell male rats took to simply trying to mount females, or even other males. Aggression increased; at times, Calhoun wrote, "it was impossible to enter a room without observing fresh blood splattered about." Central-cell females basically gave up on mothering. They built inadequate nests or none at all. When disturbed, they would start to move their babies, only to then abandon them. The pup mortality rate in the crowded cells rose to as high as ninety-six per cent. Calhoun came up with a new term to describe the process he had witnessed. The rats, he said, had fallen into a "behavioral sink."

With the barn experiment, Calhoun again cast his work as a form of sociology. In an he published in Scientific American, in 1962, he observed that research like his could, "in time," offer insights into "analogous problems confronting the human species." He didn't specify what the analogous problems were, but he didn't have to. In the early nineteen-sixties, fears of overpopulation and urban decay were rampant. At about the time Calhoun wrote his , a group of researchers at the University of Illinois decided to calculate what would happen if the number of people on the globe continued to increase along the trajectory it had followed for the previous two millennia. The researchers concluded, with a mathematical version of tongue-in-cheek, that the population would approach infinity on November 13, 2026. In the meantime, the planet would become so crowded that there would be no room to move. "Our great-great-grandchildren will not starve to death," they wrote in Science. "They will be squeezed to death."

Soon Calhoun's work was picked up by the popular press. In 1964, the Washington Post and the Washington Daily News both ran stories on it. "The world's population has been growing so fast that social scientists have been studying overcrowded rats for clues to the future behavior of mankind," the Daily News said. An influential anthropologist named Edward T. Hall became interested enough in Calhoun's work to pay him a visit. In 1966, the author Tom Wolfe spent a couple of days with Hall. The resulting essay, titled "O Rotten Gotham—Sliding Down into the Behavioral Sink," appeared in the Sunday-magazine section of the World Journal Tribune (a short-lived successor to the Herald Tribune). It described Calhoun's rat experiment at length, and took Wolfe-ish delight in describing people in ratlike terms. Grand Central at rush hour, Wolfe wrote, was filled with "poor white humans, running around, dodging, blinking their eyes."

When Hunter S. Thompson read the essay, he mistakenly concluded that Wolfe had invented the phrase "behavioral sink" and dashed off a congratulatory note. The term is "a flat-out winner, no question about it," Thompson wrote. "Every now and then I stumble on a word-jewel; they have a special dimension." References to Calhoun's work kept popping up, both in the press and in academic journals. "Today, one can hardly pick up a newspaper without reading about a new study on the effects of crowding," Hall observed in 1968.

It is estimated that, in the year 1600, there were half a billion people on the planet. It took another two centuries for the number to reach a billion, then just a little more than a century for it to double again, to two billion. By the late nineteen-sixties, it was approaching four billion. This pattern of growth is what led the University of Illinois researchers to predict "doomsday" on November 13, 2026, which happens to be a Friday. (The global population has, by now, doubled again, to eight billion, though the rate of growth has slowed.)

Calhoun was deeply influenced by the "doomsday" paper; according to Dugatkin, he "read and reread" it. And he was convinced that his rats were issuing a dire warning. At the same time, he was dismayed by the gloomy tone of the conversation his work had helped inspire. In 1969, he attended a conference on population, the environment, and human well-being. The conference minutes note that Calhoun tried to disassociate himself "from the attitude of pessimism which he felt pervaded our meeting."

Population growth wasn't the only development in human history that attracted Calhoun's attention. As towns and cities had become more crowded, people had discovered, in his words, "a new kind of space" they could move into. This was the space of ideas. Calhoun viewed the Renaissance, the Enlightenment, and the Industrial Revolution as a series of conceptual reorientations that had occurred at progressively shorter intervals. What was needed next—and fast—was a "communication-electronic revolution" that would open up more creative real estate. After that would come a "compassionate revolution," which would usher in an era of peaceful population decline. The two revolutions, Calhoun believed, were related. The conceptual space required for the compassionate revolution was so great that human brains would need electronic assistance. Calhoun imagined "thinking prostheses" that would connect "more and more individuals in a common communication network." When the compassionate revolution came, he wrote, it would "mark the termination of the past 50,000-year epic of evolution."

Another big influence on Calhoun was "The Structure of Scientific Revolutions," by Thomas Kuhn. In the book, which appeared in 1962, Kuhn divided science—and, by implication, scientists—into two types. There was "normal science," which extended and refined some established theory, or, in Kuhn's terminology, paradigm. Then there was revolutionary science, which overturned a paradigm. Calhoun clearly aspired to participate in the second sort. He took to calling himself an ℞evolutionist, which, he explained, was "a new type of 'revolutionary,' where ℞ is the prescription for, or design of, evolution." He decided to try to engineer the "conceptual evolution" of rats with an experimental setup that would force the animals to coöperate to get at food and water. The collaborative rodents would, he thought, become smarter—"I propose to make an ape out of a rat," he wrote—and this would help them counteract the deleterious effects of crowding.

In 1974, Calhoun took a sabbatical from the National Institute of Mental Health, where he had worked for the previous two decades. During his time off, he decided to attempt a "frontal attack" on the development of a thinking prosthesis. For the "communication-electronic revolution," he realized, new ways of retrieving data would be needed. He pored over stacks of academic s he had collected, trying to come up with a way to index them. This turned out to be more difficult than he had anticipated. Meanwhile, of course, computers were improving apace.

When Calhoun returned to the N.I.M.H., he found that support for his ideas was waning. The agency had been restructured and had a new focus on practical results. It cut his funding and eventually evicted him from his rat-experiment space. Calhoun resigned from the agency in bitterness in 1986. He died in 1995, while travelling with his wife in New Hampshire.

What did all this amount to? Neither "Rat City" nor "Dr. Calhoun's Mousery" seems quite sure. In the preface to the former, Ramsden and Adams explicitly say that they are not going to "evaluate the merit" of Calhoun's work. In the epilogue to the latter, Dugatkin tries to explain why this work has "fallen off the map." His explanation largely has to do with shifting norms in academia. The study of population dynamics and behavior, he writes, has "changed radically since Calhoun undertook his experiments."

Then there's the question of what Calhoun was actually observing. The pathological behavior of his rats was, it seems, a product less of their natural tendencies than of his experimental design. "No evidence" for behavioral sinks has ever "been found in wild populations of animals—rat, mouse, or otherwise," Dugatkin writes.

And, even if Calhoun's experiments did reveal something real about rodents, it's unclear what relevance this would have had for humanity. A textbook titled "Forty Studies that Changed Psychology," by Roger R. Hock, contains a section on Calhoun's work. It cautions, "We must always be careful in applying animal research to humans." In 1975, the textbook reports, researchers attempted to "replicate with people some of Calhoun's findings" by analyzing statistics like birth rates and mental-hospital admissions among New Yorkers: "No significant relationships were found between population density and any form of social pathology."

As for Calhoun's "revolutions," the one involving electronics and communications has by now, it seems, occurred. Whether or not Calhoun proposed "an early version of the world wide web," as Dugatkin claims, the Internet has certainly linked "more and more individuals in a common communication network." And, it could be argued, our increasingly intelligent laptops and cell phones count as "thinking prostheses." But where, oh where is the compassion?

Facebook, Yik Yak, Twitter, Twitch—each had a sunny, expansive phase, followed by a descent into flaming, catfishing, and troll wars. To the extent that Calhoun's rats have any sociological relevance, it would seem to be in the mirror world of the Web. What, after all, could be a better description of X these days than a "behavioral sink"?