How does Pi explain the reason as to why the hyena and Orange Juice are ignoring each other?

From the text:

"The ecosystem on the lifeboat was unreal. Where else would an orangutan and a hyena live together? A tree-dweller living with a savanna-dweller? They must have so radically carved out their niches as to pay no attention to each other. Surely an orangutan would be a sense of prey for the hyena, because it was probably better than an exhaust pipe. And surely a hyena would be a predator to an orangutan. But nature holds surprises, wait, perhaps not. If goats and rhinos can live together, can't hyenas and orangutans? A sign would have to be put up saying that the public were not to be afraid for the orangutans because they lived in trees and aren't afraid of hyenas. The public could come at feeding time where they would see the orangutans come down and walk around in front of the hyenas."