DNS, regular feedings do not emulate "kill and eat, or die." Really, they don't.
Check Aesop's "The Hound and the Hare."
When the man chastises the hound for letting the hare escape, the hound says,
"You must understand, I was only running for my dinner. The hare was running for his life."
The willingness of regularly fed, healthy zoo animals to face a threat rather than flee is not likely to be the same willingness a pack in the wild, that must kill or die, is likely to have.