Pet Theories and Pet Peeves in the Company of Animals by James Serpell

James Serpell puts the U.S. gross national pet product at $7.5 billion a year. The figure covers the cost of food and veterinary services for 475 million cats, dogs, birds, rodents, reptiles and aquarium fish. Presumably there are extras such as doggy spas, rhinestone collars, pooper scoopers and what professionals in the domestic-animal world might call alternate-species entombment. The costs are proportionately staggering in the households of the European Community, home to an estimated 91 million nonhuman inhabitants, excluding unwelcome vermin.

None of this makes much practical sense, says Serpell, a research associate in animal behavior at the University of Cambridge....