The study details how researchers picked Baltimore alleys - mostly older neighborhoods known from previous studies to harbor rats in ample supply. Or, as the paper describes them in the kind of language that would make a real estate agent faint: "Areas characterized by row houses with small backyards comprised of concrete parking pads and small garden areas often occupied by rat burrow systems." The lucky areas had what the researchers estimated was, on the average, a density of about 50 rats per alley.
Glass's interest in rats comes from a public health rather than a cultural standpoint. While the rest of us view rats as horrid creatures that basically spread revulsion, he studies them for how they spread viruses and bacteria. Although most rats don't stray much, enough do - they're known as the "super spreaders" - that they remain potential carriers of various diseases.
Still, I have to ask Glass: Why does the rat, unlike the chicken, generally not cross the road?
