What is the terror of the wild wood?

From the text:

"Well, of course—there—are others," explained the Rat in a hesitating sort of way. "Weasels—and stoats—and foxes—and so on. They're all right in a way—I'm very good friends with them—pass the time of day when we meet, and all that—but they break out sometimes, there's no denying it, and then—well, you can't really trust them, and that's the fact."