I used to be an assistant curator at a wildlife sanctuary and we had black rat snakes. They're a native species even up north here in Connecticut. A related species is the corn snake (Elaphe guttata) that is common in the pet trade. That snake is also known as the red rat snake. I actually have one in my classroom and it's the largest specimen I've ever seen. It's over 6' long, close to how big a black rat snake can get.