Why did General Zaroff walk away, leaving Rainsford safely in the tree, during the first part of the hunt in "The Most Dangerous Game"?

Robert Connell's short story "The Most Dangerous Game" details a deadly hunt involving two men. Sanger Rainsford, a big game hunter from New York City, accidentally falls off his yacht and swims to a nearby island where he meets General Zaroff, who lives in a large mansion with his servant Ivan. Zaroff is a Cossack who has fled Russia after the revolution. His passion in life is to hunt. Unfortunately, he has become bored with...

Robert Connell's short story "The Most Dangerous Game" details a deadly hunt involving two men. Sanger Rainsford, a big game hunter from New York City, accidentally falls off his yacht and swims to a nearby island where he meets General Zaroff, who lives in a large mansion with his servant Ivan. Zaroff is a Cossack who has fled Russia after the revolution. His passion in life is to hunt. Unfortunately, he has become bored with hunting animals. Because he has grown so good his passion begins to tire him. He cannot find an animal that provides the challenge he craves. He describes to Rainsford his problem while he was hunting jaguars in the Amazon:

"They were no match at all for a hunter with his wits about him, and a high-powered rifle. I was bitterly disappointed. I was lying in my tent with a splitting headache one night when a terrible thought pushed its way into my mind. Hunting was beginning to bore me! And hunting, remember, had been my life."

So Zaroff comes to the island to hunt men who are ship wrecked. When he suggests to Rainsford that they hunt together, the American is repulsed and refuses. Zaroff then decides to hunt Rainsford and is quite excited about the prospects of matching wits with another hunter. Zaroff says,

"You'll find this game worth playing," the general said enthusiastically. "Your brain against mine. Your woodcraft against mine. Your strength and stamina against mine. Outdoor chess! And the stake is not without value, eh?"

The general sets Rainsford loose on the island armed only with a good hunting knife. For a time, Rainsford is shocked and runs aimlessly. When he finally gathers himself, he winds his way through the jungle and creates a trail which would be impossible to follow for anyone, except, of course, the general. Rainsford is  perched in a large tree when the general comes slashing through the brush and stops just below. The general lights a cigarette while he examines the tree. Zaroff smiles and then walks away. He leaves because he hasn't finished having fun with Rainsford. He doesn't want the hunt to end so quickly and is probably impressed by the difficult trail Rainsford cut through the jungle. He wants to see how else the American might choose to elude him. Zaroff lives for the "game."