This exhibit and the adjacent exhibit, which at the time of my visit still housed the tigers that moved to their new exhibit a few weeks later, are destined to eventually be demolished for the zoo's planned new chimpanzee facility.
@Arizona Docent The picture is a little deceptive in terms of the height of the fence, in reality it looked substantially taller than it does here. But to me it does a bit lower than the fence around an enclosure that housed mountain lions for years (now cheetah exhibit).
That said, I did ask myself that same question earlier today when processing the pictures. What's secure enough for tigers wouldn't necessarily be enough for a determined mountain lion. I'm afraid I don't really have an answer for you. But I don't think this zoo could afford a dangerous animal escape incident, given its muddled history.
Perhaps the fact the exhibit is mostly moated could help also? I think mountain lions might be more easily deterred by water than tigers would be?
I didn't realize the dark green in front is water. I thought it was some kind of ground substrate. That makes more sense, although the side fence viewable in the back of the photo still doesn't look that secure.
