CM told me once about a bunny that got into the Komodo dragon enclosure at AK. A guest started screaming at the CM telling her to rescue the poor little thing because, sure enough, the komodo started eating it! The CM was all - "you DO realize that is the largest and most deadly lizard in the world, right? I am SO not going to save a RABBIT just for you and risk my life!"
The guest just had a fit and even got so mad that she wrote a letter to the WDW stating how horrible and evil the cm was for not saving the poor rabbit from it's Darwin destiny! The managers at the AK area got the letter forwarded to them, and everyone had a good laugh about it. Apparently, despite Disney's best efforts, Floridian animals that fail their "survival of the fittest" test still get into enclosures and get eaten. The cm's just radio back to the zoo handlers/feed people that animal X ate X number of bunnies/birds/snakes/etc and then the animal's food gets cut down that day, or they get a trip to the vet, depending on x eaten animal!