I think perhaps they might want to implement them as actual animals rather than effects. Would be nice if guests would recognise them as more than scenary.
I just don't see how they could possibly do that. Making them effects seems like the most practical way to go. Looking at what the exhibits currently are, you wouldn't see a real zoo keep butterflies or bees in something like that (maybe the caterpillars/cocoons/a display of the beehive, but not the animals themselves). At least, every butterfly display I've ever seen has them in a big free-flight building full of tropical plants and the like, where they can behave naturally (and even then it's usually only non-migratory species).
At least as effects they can do a lot to flesh the zoo out and make it 'breathe' a little more (I'd support a looping effect even for some fish if it came to it - something that brings a little life to certain parts of the zoo without requiring any real management).