Wild animals that are captured when they are fully mature are another example of escape-prone animals; often they are too set in their ways to reconstruct their subjective worlds and adapt to a new environment.
But even animals that were bred in zoos and have never known the wild, that are perfectly adapted to their enclosures and feel no tension in the presence of humans, will have moments of excitement that push them to seek to escape. All living things contain a measure of madness that moves them in strange, sometimes inexplicable ways. This madness can be saving; it is part and parcel of the ability to adapt. Without it, no species would survive.
Whatever the reason for wanting to escape, sane or insane, zoo detractors should realize that animals don't escape to somewhere but from something. Something within their territory has frightened them - the intrusion of an enemy, the assault of a dominant animal, a startling noise - and set off a flight reaction. The animal flees, or tries to. I was surprised to read at the Toronto Zoo - a very fine zoo, I might add - that leopards can jump eighteen feet straight up. Our leopard enclosure in Pondicherry had a wall sixteen feet high at the back; I surmise that Rosie and Copycat never jumped out not because of constitutional weakness but simply because they had no reason to. Animals that escape go from the known into the unknown - and if there is one thing an animal hates above all else, it is the unknown. Escaping animals usually hide in the very first place they find that gives them a sense of security, and they are dangerous only to those who happen to get between them and their reckoned safe spot.