According to Pi, why does the hyena not eat him or the zebra immediately?

"Pi hears snarls coming from the hyena and barks from the zebra, as well as wet mouth sounds". "Still the animals do not come near him. He hears sounds from under the boat and notes that the animals in the water are also battling for life." "After that first full night in the lifeboat, the sun rises, and Pi's thoughts turn to rescue and seeing his family again. But when he looks into the lifeboat, he sees an appalling sight: the hyena has bitten off the zebra's broken leg and is eating it. The zebra is alive, still silent but grinding his teeth." I feel like the hyena was waiting for the right time, to attack the zebra. And that the hyena didn't wanna attack him because someone could find him when it is light outside because it said " In the dark, a rescue ship won't be able to spot him, and the animals might attack him.