Your Bunnies need energy to dig, mine and breed. Energy can be gained by either feeding your bunnies food or by placing them on certain furniture that can regenerate energy over time. Energy will restore completely to the max energy your bunny can hold when the specific bunny levels up. At every level, your bunny gains 10 energy. Energy is calculated using this mathematical formula: BUNNY LEVEL x 10. Digging more deeper will result in more energy loss for your bunnies.