When dining with Zaroff on the night that Ivan finds him and brings him to the mansion of the general, the reader notes a distinct difference in the point of view expressed by the two hunters: Zaroff states that, bored with hunting, he needed a new animal, one that can reason. Understanding the implication of what Zaroff has said, Rainsford, appalled, replies, "Hunting, ...what you speak of is murder...[I do] not condone cold-blooded murder...I'm a hunter, not a murderer." The irony, of course, is that at the end of the story, Rainsford does, indeed, become a murderer, too.
Another irony is that Rainsford does not really know himself, for in the exposition he tells his shipmate, "The world is made up of two classes--the hunters and the huntees." This statement foreshadows the self-prophesy of Rainsford's predatory self when placed in a life-threatening situation. In the end of the story, he has accepted that he is a predator. In fact, he relishes his role: "He had never slept in a better bed, Rainsford decided."
What Zaroff has already known and accepted about himself, Rainsford has to discover when he becomes "an animal at bay." In essence, the two mean are alike, both predatory, but Rainsford does not realize this similarity until the end.
both expert hunters
they have hunted all kinds of animals
zaroff belives hunting humans is only hunting, just like any other animal
while rainsford belives its murder