Ben Dantzer had spent several frustrating days trying to capture a single squirrel when the epiphany arrived. Dantzer, a rodent researcher at the University of Michigan, was standing in the Canadian Yukon, scrutinizing the uncooperative squirrel, which was perched high in a spruce tree. Then, all of a sudden, he felt as though he was looking at an optical illusion: When he viewed the squirrel one way, he saw a squirrel; when he viewed it another way, he saw a rat. “I kind of think of squirrels as rats in costumes,” he told me. “Like with a fur coat and a dog’s nose.” It’s true: The two rodents do look remarkably alike. And yet, for all their similarities, they elicit wildly different reactions from humans. Squirrels—aww. Rats—ick. What gives?
People have been pondering this question for years. The absurdist TV series Portlandia takes it up in a sketch featuring three hipster rat puppets confounded by the preferential treatment afforded to their bushy-tailed brethren. Christoph Waltz, playing a Nazi colonel, deploys the enigma to justify the Holocaust in the opening scene of Inglourious Basterds. “You can’t make friends with a squirrel,” Sarah Jessica Parker declares on Sex and the City. “Squirrels are just rats with cuter outfits.” Numerous Reddit threads and Quora posts have also posed the question in one form or another, prompting lots of impassioned (and sometimes implausible) hypotheses. Debates devolve. The gloves come off. Things get ad hominem—or rather, ad rodentem.
Not everyone accepts the popular consensus on rats and squirrels. There are those who reject it on the grounds that rats are actually cute—“Just like tiny dogs!” they say. “The sweetest little guys around.” Once, Juan Sanguinetti-Scheck, a rodent researcher at Harvard, stopped oncoming traffic to save an injured baby rat … while on a date. (“She was very supportive,” he assured me.) Then there are those who argue that squirrels are actually gross—“tree rats,” they call them, distinguished from their sewer-dwelling cousins only by some minor technicalities. These detractors note that squirrels are responsible for up to one in five American power outages, cause thousands of house fires a year, and, from time to time, indiscriminately attack humans. “Squirrels,” one Redditor writes, “are total dicks.” Such antipathy is nothing new. In 1918, California conscripted children into a week-long war on squirrels. “All the killing devices of modern warfare will be used in the effort to annihilate the squirrel army,” vowed one local newspaper. “Including gas.”
But that’s not really the point. The point is that most people seem to acknowledge that whatever their personal feelings about these critters (and don’t even start on mice or gerbils or capybaras), public opinion skews pro-squirrel and anti-rat. The question is why.
Let’s start with the obvious: the tail. The squirrel’s is big and bushy, the rat’s is naked, scaly, and wormlike. This tends to be the first thing that comes up in any conversation about our attitudes toward squirrels and rats. Just look at a squirrel’s tail! “You gotta admit,” one Quora commentator writes, “that’s pretty darned cute.” A rat’s, not so much. And the underlying principle here seems to hold true across species, not just for rats and squirrels. Name one fluffy animal that humans find gross … see? (Etymology lends credence to the notion that fluffy tails are perhaps the essential characteristic of squirreldom: The scientific name of the American red squirrel, Tamiasciurus hudsonicus, translates to “the steward who sits in the shadow of his tail.”)
Also working against rats are where and when we generally encounter them—wrong place, wrong time. Unlike squirrels, which we tend to see in the light of day, rats are nocturnal. We encounter them in the dark, when we’re most susceptible to fear, Sanguinetti-Scheck pointed out. “When we see a rat at night, we mostly encounter it by accident, and it stuns us a bit,” he said. “That changes a lot about how you look at an animal.”
And whereas squirrels mainly stick to parks and wooded areas, rats permeate the whole urban landscape. (New York City alone has 2 million of them.) They rustle around in trash cans and take up residence in sewers, which feeds the false impression that they are fundamentally dirty creatures. Worse still, they invade homes and other indoor spaces. Squirrels do this too—given the opportunity, they’ll wreak havoc in your attic—but not as frequently. And if you are what you eat, then squirrels (acorns, nuts, fruits, seeds) surely win out over rats (garbage, carrion, insects—you name it).
Another popular hypothesis is that squirrels just flat-out run a better PR operation. In other words, their superior status is not innate but cultural, resulting from a long history of favorable media depictions. They regularly feature in children’s books and movies, where they’re usually portrayed as resourceful and industrious. Rats, on the other hand, are almost always cast as villains—okay, yes, with the notable exception of Ratatouille. So strong are the negative associations that the word itself has become a pejorative for someone deceitful or disloyal.
All of these theories likely have some truth to them, and that’s because they’re all intertwined. The underlying mechanism at the core of our rat aversion may be disease avoidance, Jakub Polák, a psychologist at Charles University, in Prague, who has studied the relative grossness of different animals, told me. Disgust, Polák said, evolved as a defense mechanism against dangerous pathogens—and rats are notorious transmitters of disease. They’ve long borne the brunt of the blame, deserved or not, for the bubonic plague. And they can also carry a number of other infectious diseases, including hantavirus, leptospirosis, lymphocytic choriomeningitis, tularemia, and salmonella.
Squirrels, too, can carry diseases, Dantzer said, but they don’t seem to transmit them to humans at the same scale that rats do. This is not to say that when people see a rat, they consciously think, I better avoid that creature, given its history as a vector of disease. They don’t really think at all. They just recoil … or scream … or faint.
Disease avoidance, then, is not so much an alternative to as a grounding for the above hypotheses. Take rat tails: The reason they repulse us, Polák posits, is that they remind us of other organisms that we have evolved to find repulsive for our own protection—snakes, worms, parasites. But in the mystery of squirrels versus rats, the tail itself is a bit of a red herring, he says. It is probably not the cause of our aversion; instead, we likely latch on to it as a visual cue to justify our antipathy.
Even the PR hypothesis, seemingly at odds with the idea that our attitudes toward rats and squirrels have an evolutionary origin, fits into this story. Disease avoidance helps explain how our anti-rat culture came to be in the first place, the University of Michigan psychologist Joshua Ackerman told me. And that culture in turn helps ingrain the genetically inherited predisposition to find rats gross.
Whether disease avoidance alone supplies a complete explanation of our feelings about rats and squirrels, though, is an open question. Polák thinks so. Paul Rozin, a University of Pennsylvania psychologist and a pioneer of modern disgust research, is not as sure. For evidence, he points to the fact that what is delicious in one place is nauseating in another. In many Asian countries, rats are just another source of protein; in some, the tail is a particular delicacy. Disgust, in Rozin’s view, emerges from a complex combination of cultural and evolutionary forces—and maybe even other factors we have yet to identify. “It’s a complicated world,” he told me.
Discussion in online forums about the rat-squirrel question certainly bears that out. “Since I love them,” one Quora commenter writes, “I don’t actually mind waking up to find a rat standing on my face.”