With today's world facing an unprecedented biodiversity crisis, our cities are becoming hybrid jungles, alternative habitats for a good many forest creatures. Berlin's parks are home to 33,000 unplanned wild boars, and leopards live on the outskirts of Bombay. Some species have either physically or behaviorally mutated for urban survival: Brooklyn's mice are resistant to heavy pollutants, Barcelona's snails can survive urban heatwaves, and Lima's vultures have turned into team players. Now it’s our turn to transform our environment and forge alliances with these imperiled guardians: our cities' fur-clad, feathered, cold-blooded bioengineers and gardeners.