Their is just enough of a distance between everything around that they normally won't try it. One set of nearby trees does grow tall enough every few years that a couple of young males do try and escapes have occurred but they get caught up and returned pretty quickly.
I was genuinely astonished when I realised the langurs had full access to this tree. It doesn't surprise me that escapes have occurred. There is no doubt that it's an arresting exhibit.
