In downtown Chicago, a coyote spends his entire life in one cemetery, eating chicken that Sunday mourners place on the graves. On Manhattan sidewalks, ants survive on hot dogs and potato chips, seemingly no worse for the junk food diet. And in Los Angeles, a mountain lion roams the Hollywood Hills, tiptoeing around throngs of tourists without ever being seen.

As people flock to cities like never before—six billion will live in urban areas by 2045—they're not alone. Attracted to plentiful food and mostly protected from hunting, among other natural dangers, a veritable menagerie of creatures also calls cities home.

And these new urbanites, ongoing research shows, are learning how to change their lifestyles—sometimes dramatically—to suit ours.

Several urban