In many fields of science, it’s always the year of the rat

On the Chinese zodiac calendar, 2011 was the Year of the Rabbit. For scientists it was more like the year of the rat. A seminal study published in Science demonstrated that rats aren’t the conniving, selfish creatures that popular culture has long made them out to be. Rats will liberate another rat from a locked cage, researchers found, even when given a choice to gorge on chocolates instead.

Perhaps humans should extend some similar graciousness to rats. Rats have long been maligned in literature, movies and popular expressions. Take Templeton, the gluttonous rat in Charlotte’s Web, who helps Wilbur and Charlotte only when he realizes that without Wilbur, there will be no food to steal from the pig trough. Or Rat, in Roald Dahl’s Fantastic Mr. Fox, a selfish drunk concerned only with his next sip of cider, not the welfare of his trapped animal comrades.

Selfishness, however, is the least of the rodent’s PR problem. For rats gone really wrong, there are movies like Deadly Eyes, Willard and Ben, wherein the rodents are tools of terror, demolishing grocery stores and attacking and eating people.

Rats are also regularly impugned in everyday language. The plural form serves as an all-purpose (albeit a mild) curse word. To express general disdain, there’s the handy “not giving a rat’s” posterior. And when suspicion arises of a traitorous foe, there’s that staple of spy thrillers and police dramas: “I smell a rat.” This expression dates back at least as far as Cervantes’ Don Quixote and purportedly stems from the stellar ability of dogs to sniff out rodents, rather than the odiferous properties of rats. Which, if you ask a scientist, makes sense.

“Rats are clean and they don’t smell,” says Nicole Stricker, who studied the mechanisms underlying memory in rats for her neuroscience Ph.D. at Johns Hopkins University. “It’s mice that stink. You walk into the mouse room and it just hits you. But people aren’t grossed out by them because they are cute.”

In an informal survey of several researchers who have worked with both mice and rats, rats win hands down. “Rats don’t pee on you or bite you when you pick them up,” said one researcher. “They’ll crawl in your pocket and sit on your shoulder. Rats are friendly. I don’t know why people don’t like them—I think it’s the tail.”

Granted, rats have played a role in spreading some of history’s most infamous diseases. Rats can carry fleas, which carried Yersinia pestis, the bacterium responsible for the bubonic plague. But cute little mice carry diseases as well—white-footed mice (don’t they sound sweet) are the preferred rodent host of the ticks that carry Lyme disease. And deer mice are the primary carrier of hantavirus in the United States. But mice are thought of as darling, harmless creatures, and in colloquial use, mouse is typically a term of endearment.

Yet both rodents have had an immeasurable effect on science and medicine. The laboratory rat, Rattus norvegicus, was the first species of mammal domesticated for scientific research, an endeavor that dates back at least to 1850 and has led to numerous new medicines and procedures, not to mention a greater basic understanding of how our bodies and brains function. There are more than 500 special strains of rats, bred for studying diseases such as addiction, diabetes, arthritis, kidney disease, heart failure, multiple sclerosis, sleep apnea and lupus. Rat brains are more complicated than mouse brains, making them better candidates for studying complex diseases such as autism and Parkinson’s. And rats’ larger size makes them the preferred rodent for organ transplantation studies. While the mouse was long favored for genetics research, thanks to their quick breeding time and interesting coat color traits, rats are gaining ground in that area as well: Scientists deciphered the rat’s genome in 2004. That blueprint, along with the ability to coax stem cells from rats, is making it even easier to use them as models for investigating human disease.

So maybe we should take a page from the Chinese astrologers or from the occasional film or book that casts rats in a favorable light. Of the 12 animals in the Zodiac, rats (not mice) occupy the first and most prominent position. Rats symbolize character traits such as wit, wisdom and imagination; they are considered charming, smart and extremely loyal to friends and family—traits exemplified by the Muppet Rizzo the Rat, and Remy, the budding chef in the animated film Ratatouille. Remy’s efforts were ultimately rewarded and earned rave reviews. We owe lab rats the same accolades.

SN Prime January 23, 2011 | Vol. 2, No. 3

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