It mostly depends on the seetings you choose mroe than the map script. Animals will spawn if their are big unexploded areas and there arent many cities ont he map (after there get over a certain amount of cities barbs spawn instead of animals).
So animals will be less likely if:
1. You add more civs to the map than the default.
2. You use advanced start.
3. You play barbarian world.
4. you dont start in the ancient age.