On July 9, 2015, a dead raccoon appeared on a Toronto sidewalk and, for reasons no one fully understood, four men from a nearby office decided to hold a funeral. They bought a cellophane-wrapped rose, signed a card, and placed it on the corpse, whom they named Conrad. In “Our Wild Familiars” (Crown, out Tuesday), Dan Werb uses Conrad’s wake as the doorway into an exploration of synanthropes — a term derived from Greek that means “together with man” and is used to describe wild creatures who have found niches in human-built cities. “I love the story of Conrad, because it’s so unlikely and revealing,”…