The Great Mortality: An Intimate History of the Black Death, the Most Devastating Plague of All Time

by John Kelly

the black rat usually travels by night, builds an escape route in its den, and reconnoiters carefully. This last behavior seems, at least in part, learned. During a foraging expedition, one young rat was observed taking a reconnaissance lesson from its mother. It would scamper ahead a few feet, stop until the mother caught up, then wait as she examined the floor ahead. Only after receiving a reassuring maternal nudge would the young rat advance. Rats also have another rather unusual, humanlike trait: they laugh. Young rats have been observed laughing—or purring, the rodent equivalent of laughter—when playing and being tickled. Rattus is, by nature, a very sedentary animal—usually. A city rat may wonder what lies on the other side of the street, but studies show it won’t cross the street to find out.