You're right- Apes(and other species too) will live behind certain barriers quite happily until some unusual circumstance(such as the above) happens which causes them great stress leading to unusual evasive action- like crossing water, jumping a wide ditch or climbing a wall.
There was a film(Urban Gorilla) some years back that showed a young female Gorilla 'Rapunzel' at the Los Angeles Zoo being introduced into an adult group. The enclosure was a converted grotto -style bear pit with a wide dry(?) moat. The male 'Tzambo' attacks her and picks her up in his teeth. She breaks away and to escape him she takes an enormous flying leap at the moat and nearly manages it but falls back down(she was not badly hurt by the experience)
My point is she would probably never have made an extreme action like that under normal non -stressfull conditions.
There was a film(Urban Gorilla) some years back that showed a young female Gorilla 'Rapunzel' at the Los Angeles Zoo being introduced into an adult group. The enclosure was a converted grotto -style bear pit with a wide dry(?) moat. The male 'Tzambo' attacks her and picks her up in his teeth. She breaks away and to escape him she takes an enormous flying leap at the moat and nearly manages it but falls back down(she was not badly hurt by the experience)
My point is she would probably never have made an extreme action like that under normal non -stressfull conditions.