Suddenly…

Now this could be interesting.
We see alot more gem related animals (like the gem-shard creatures, that lizard thing lion ate, and whatever lion is) than regular animals ( also all the marine animals we saw in bubble buddies, and siluets of whales in lion 2)

So maybe gem-altered animals have a distinct advantage over their mundane counterparts and have out competed most of them?

More likely is that we simply don't see them very often similar to how we don't see many animals wandering in towns irl

also Raccoon from On the Run, and the Snake+Mouse of Onion Friend.