Seagulls attacking doves in St. Peter’s Square in Rome. Sparrows at dawn, swooping down on foolish young geckos that lingered too long on the walls of ancient Venetian palaces. Foxes living stably in the heart of many European cities, wild boars that roam freely from northern to southern Italy and, at times, even wolves that leave the hills and mountains, straying close to residential areas. By now there is so much zoology in our cities. Mammals, amphibians, reptiles, birds, invertebrates and fishes are the urban fauna that, along with the flora, have created biodiversity with a wealth of species that have become part of our lives. Wild and domestic animals, entering spontaneously or introduced in various ways into our cities and suburbs. In addition to changing their habits, they have changed our landscapes and behaviour. With simple language and his usual scientific rigour, Mainardi explains the reasons for this colonization and dwells upon the adaptations that our non human “roomies” acquire with their new urban life concerning social behaviour, ways of reproducing and raising their young, diet and procuring food. A famous ethologist, Mainardi believes that the cities of the future will be increasingly multi-ethnic (animals, humans), but also multi-racial (domestic animals) and multi specific (wild animals), and only by thoroughly knowing our “fellow citizens” we can all live together happily.