R.O.U.S.

Rodents Of Unusual Size, also called R.O.U.S.s, are giant rat-like creatures that live in fire swamps.

Physical description
In the book, fire swamp R.O.U.S.s are described as "a pure rat strain", usually weighing 80 pounds, and running as fast as a wolfhound, about 40 miles per hour.

They are also carnivorous, and can attack in a frenzy. They are dangerous, but only attack if they smell blood or outnumber their opponent.

Role in the book
While Westley and Buttercup travel through the swamp trying to get back to Florin, Westley tells Buttercup how he became the Dread Pirate Roberts. As he tells her, he notices an R.O.U.S. is following them. A second one soon follows; both of them notice, but Westley assures her he is watching them.

As he finishes telling her his story, a third R.O.U.S. pounces on him, knocking him to the ground, and biting into his shoulder. He rolls it into a flame spurt, burning it before using his sword to stab it in the heart; the other rodents, drawn to the smell of blood, start to devour the burned R.O.U.S. alive before Westley slays them. As Buttercup patches Westley's wound, four more R.O.U.S.s arrive; Westley kills one of them before he and Buttercup escape.

Role in the film
In the film, an R.O.U.S. arrives at a lightning sand pit after Westley and Buttercup become submerged. When they emerge, the rodent is joined by another one, growling disgruntledly at them. Westley notices the rodents, and starts leading Buttercup away from the area, talking about the dangers of the fire swamp; when Buttercup brings up R.O.U.S.s, Westley doubts their existence.

No sooner does he say that then an R.O.U.S. launches itself off a tree branch at Westley, knocking him to the ground and biting his right arm at the shoulder. While a horrified Buttercup stands aside, Westley eventually rolls onto one of the flame spurts, burning the rodent. Westley then kills the weakened rodent by stabbing it three times with his sword.

Behind the scenes
In the 1987 film, the rodent that attacks Westley is portrayed by Danny Blackner, while the second one was played by Anthony Georghiou.

The vocal effects were provided by director Rob Reiner.