When should I go to the Savannah?

[Hroar the Red]

Is there a certain evolutionary stage I should wait until?

[RCMidas]

Not really. The later you leave it and the more mutations and reinforced neurons you have, the easier you'll find surviving it, but you can exist there as a Missing Link if you play smart. Just watch out for loads of hyenas and really irritable buffaloes, rhino and elephants.