What they really should have done was have surveillance cameras linked to the tour vehicles so the visitors could always see the animals even if they weren't nearby. But, in the film it looked like the Park's engineers assumed that the carnivores would always come when food was placed out for them, though it didn't turn out to work that way in reality.
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Visit the lovely Second Earth!
The Forgotten World Characters: Cessna (Pteranodon longiceps masranii ♀)