One late night/early morning several years ago I was driving through Golden Gate Park when an animal appeared in my headlights. It was moving away from me so all that I could see at first was its rear end. Most noticeable was a long, long, skinless tail and a huge rump. My first thought was "Holy %$*&, that's the biggest rat I eve saw. A few moments later, when it turned sideways I recognized it as a possum. I felt a lot better about sharing the park with a critter that plays dead when startled than a rat the size of a possum.