When you make an exhibit, place three large rocks (which satisfy most animals, but not all --the warthog which is happier with more) and put all the foliage in one corner and a few others scattered through the exhibit but quite a bit apart. If you clump it all in one corner, once the animals are in the green bar with happiness, with thier foliage stop. Doing this with two or three exhibits will easily win you the award.