This project is no longer maintained, feel free to fork the repo and continue.
Modpacks: You may use my mods in your modpacks. I would appreciate credit for my mod.
Turtles will spawn in all suitable biomes that are derived from the BiomeGenBase class. This means turtles will spawn in biomes from the ExtraBiomesXL mod. Turtles will not spawn in cold biomes, or the Nether or the End. Turtles are passive mobs, no taming or breeding.
Desert Tortoise:
This is a small Desert turtle that spawns in desert biomes.
Giant Tortoise:
These can spawn in most biomes that are not snow covered. 
Small Turtle:
These can spawn in most biomes that are not snow covered
The TurtleMod Team
