In "The Most Dangerous Game", what does Rainsford learn from his experience at Ship-Trap Island?
I think Rainsford definitely learns what a human feels like when he/she is being hunted. In the beginning of the story, Rainsford and Whitney are discussing their upcoming jaguar hunt. Both men are excited about the hunt, but Whitney expresses sympathy toward the feelings that the jaguar is going to experience.
"Even so, I rather think they understand one thing--fear. The fear of pain and the fear of death."
"Nonsense," laughed Rainsford. "This hot weather is making you soft, Whitney. Be a realist."
The above lines also show Rainsford's response. Rainsford not only dismisses the possibility that animals feel fear, but he also insults Whitney for even considering such a concept.
When Zaroff and Rainsford discuss hunting, Zaroff tells Rainsford that hunting humans and other animals is basically the same thing. The only difference that Zaroff allows humans is the ability to reason.
"That is why I use them. It gives me pleasure. They can reason, after a fashion. So they are dangerous."
I believe that Rainsford agrees with that analysis of humans. It's why Rainsford realizes that Zaroff is hunting humans before Zaroff admits it.
"But no animal can reason," objected Rainsford.
"My dear fellow," said the general, "there is one that can."
"But you can't mean--" gasped Rainsford.
"And why not?"
I think that distinction about humans is why Rainsford sees hunting animals as sport and hunting humans as murder.
"Hunting? Great Guns, General Zaroff, what you speak of is murder."
By the end of the story, I am certain that Rainsford has learned that his ability to reason and plan helped him survive, but I am not as certain that Rainsford's general view of hunting has changed. The previous answer states that Rainsford is now likely to consider his prey's feelings on the next hunt. That is very possible. I can't discount that. However, I think it is equally possible that Rainsford's attitude toward future prey is exactly what it was at the start of the story. Humans are different than jaguars, and his future prey aren't capable of experiencing what he experienced on Ship-Trap Island.
Connell shows that hunting is a worldwide sport through conversation between Zaroff and Rainsford. Rainsford refers to the Cape Buffalo head hanging on Zaroff's wall; later, Zaroff speaks of a gun that was specially made for him in Moscow, the bears he killed in Russia and the United States, rhinoceroses and crocodiles he hunted, jaguars in the South America, and even brags that he has (basically) hunted anything that could be hunted in every place possible.
By the end of the story, Rainsford has certainly learned what it truly means to be hunted. Near the beginning of the story, Rainsford made snide remarks regarding the feelings of a jaguar being hunted. He implied that he didn't care how the animal felt; however, Rainsford's friend, Whitney, said that the animal cared. Rainsford responded that animals don't understand, to which Whitney replied that they do understand fear. After being hunted himself, Rainsford found that Whitney had been right while he had been quite wrong. It is unrealistic to believe that Rainsford would ever again have hunted without considering the feelings of his prey and remembering what he went through on Ship-Trap Island.