In February 2006 the biologist John Marzluff and his team caught seven wild crows on the University of Washington campus to band them, and while they did it they wore a rubber caveman mask. Afterwards, anyone who walked across campus in that mask got scolded and mobbed from the trees, while someone in a different mask on the same path was left alone. That much you might expect. The surprise came over the following years: the mobbing spread. Crows that had never been caught joined in, and so did fledglings that hadn’t hatched when the net came down, because they had watched their parents yell at that face and learned it. The campus crows kept it up for well over a decade. A grudge, in a crow, turns out to be less a memory than a piece of local knowledge, handed down like the name of a bad road.