A baby bonobo ape cuddles with its mother "Kiri" in Memphis, Tenn. (Laura Horn/AP)

David Grazian spent years observing captive animals. In the process, he learned a lot about humans.

Early in his career, the University of Pennsylvania sociologist had studied and written books about nightlife in Chicago and Philadelphia. But when he and his wife had a son who grew to like animals, Grazian turned his attention to zoos — which, he concluded, “share a number of similarities with nightclubs and cocktail lounges, and not only because they all feature the public display of uninhibited mating rituals.”

He shifted his scholarly attention to zoos and their place in American culture. For several years he worked as a volunteer, shoveling manure, scrubbing cages, preparing meals.

He wandered through zoos taking notes and photographs, bringing his son along for company (and camouflage).

He examined the artificial environments of authentic animals, the zookeepers who take care of them, the volunteers who lead the tours, the children who are enchanted (or bored) by them.

Now he has written an engaging account of this segment of contemporary culture, discussing some interesting questions: Should large, intelligent mammals such as great apes be confined at all? Why are Americans so often concerned about the comfort of zoo animals when they don’t worry about the vastly greater number of other caged animals — the ones being prepared for slaughter? Beyond entertainment and amusement, what should a zoo’s role be regarding environmental protection or species conservation? “American Zoo’” is a serious book — about 20 percent of it is extensive notes and a detailed index — but Grazian’s lively, readable prose makes it entertaining as well.