We tend to think that cities, as human constructs, are the homes of humans. But they are much more than that. The modern city is actually filled with wild animal inhabitants. Squirrels, hedgehogs, pigeons, sparrows, frogs, and many more small critters live within the confines of European cities; it is their natural habitat. Livestock have also traditionally been city residents, with pigs and poultry as most common. Mice and rats receive the most frequent negative response, particularly when they take up residence inside of human houses. But in the 21st century many of the others are seen as desirable—indicators of an environmentally-friendly urban area. Our artificial structures are part of nature…