The under ground world needs more and more life to it. Seems frogs, beetles, ect... also live in cave and so on.
Found this articl that explains a little mroe then this.... I am still looking for the right one that gives the full info I want....
http://science.howstuffworks.com/life/b ... ology1.htm
But I feel every inch we move forward makes the game more fun. Even if its Spelunking in caves.