Hello gents,
I am one of the Okavango developers and the sculptor of statues.
The reason that elephants and giraffes are statues (default btw) is because the animated versions are simobjects. As they cannot move without a Worldscrip(more later) they would be stationary animated animals standing upright. In the meantime, the CPU would be doing speed, altitude and contact point calculations which would bring the FPS down to 10. This is what happened when we tried it with 6000 animals, which is less than half of what is in there.
Worldscripts: a series of waypoimts that simobjects follow. This is how we put some moving elephangs and giraffes (default) across the delta to disrupt the static displays. There is no documentation on how to create these so that forced us to use some default ones to the extent it didn’t harm fps and go static with the rest. That also applies to vehicles.
For the custom animals, we opted for statics with a bit of animation on their tails, heads or breathing. Scenery and not simobjects for the same reasons as above.
Overall, animals are clustered where you would expect to find them IRL and keeping in mind the limitations of the sim when it comes to their application and population.
You can expect to find animals more often near water bodies than away from them. Some animals are limited to certain areas (hippos in the North for example), others are just rare (rhinos) and others abundant (elephants).
I hope that clarifies some of the design decisions. The scenery is vast but has to be able to run and be seen from a low flying aircraft. When the tools, sim and hardware allow for more, we will definitely jump on it.