Achatina's are by far the hardest animals to escape on the island. Their insane movement speed is devastating to you and your dinos. These snails are also very powerful and will kill your gigas within, at least, 24 hours! The best thing to do when you see them is bola them and run.
You may find the legendary Gary by himself or with his mates while running along the beach. You can find him at South, West,and East Zones along the shores. If you encounter him tell him his homie Merk sent yall. ~Tundra
One time my tribe was taming one of these things but we were gonna be one cake short so I had to go bet more sap. Our tree sap tap turned out to be empty so I had to steal some from another tribes. I was caught and they insisted we went to war over like 20 sap. We took heavy casualties and lost the achatina that was tamed using their sap.