The restless rats return in James Herbert's Lair, the second horror novel in the Rats trilogy.
The mutant white rat had grown and mated, creating offspring in its own image. They dominated the others, the dark-furred ones, who foraged for food and brought it back to the lair.
Now the dark rats were restless, tormented by a craving they could not satisfy. But the white slug-like thing that ruled them knew. Its two heads weaved to and fro and a stickiness drooled from its mouth as it remembered the taste of human flesh . . .