If you stroll through a park in an American city, you might assume that all the squirrels you see got there on their own. After all, where there's trees, there's usually nuts, and where's there's nuts, there's squirrels. But it turns out that those nut-bearing trees were specifically planted to support squirrels, and that all those squirrels were brought there on purpose. It turns out the existence of urban squirrels is linked to a history of changing attitudes towards nature, the wilderness, and animals:
The squirrel fad really took off in the 1870s, thanks to Frederick Law Olmstead's expansive parks... the movement to fill the parks with squirrels "was related to the idea that you want to have things of beauty in the city, but it was also part of a much broader ideology that says that nature in the city is essential to maintaining people's health and sanity, and to providing leisure opportunities for workers who cannot travel outside the city." These squirrels were possibly the only wildlife the workers would ever see.