climbable area

I suppose this is both feedback and a question, but I've had these Formosan bears for many in-game years and they don't seem to climb anything. I've seen it happen in a tutorial-park, but in this one (which is the first "free-build" park) I haven't seen them climb once. At first, I put in some...

I'm mid-way through building an exhibit for my orangutans. I have finished the indoor house, which has a huge climbing structure, all working well, as shown: But now I come to build the outside part and I suddenly find that the Orangutans are unable to climb the structure that I have built...