@Chlidonias IMO these metal 'trees' some new exhibits are employing for apes don't offer that much for the apes for the cost. They dont actually create that much vertical space, and are completely exposed to the elements and devoid of privacy unlike a natural forest canopy. They are an eyesore which doesn't improve the animal welfare very much, I think they are more of an expensive novelty attraction than anything else...
@DelacoursLangur - they aren't metal trees, they are supports for the cables so that the apes have an enormous extra amount of arboreal space. Have a look at the map (the next photo along) which shows how the aerial cables cover a lot more ground than the actual enclosures do.