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The appendages on Nidolous's back help it detect vibration shifts in its environment, allowing it to defend itself in combat. If one head makes a decision that messes up the other one, the two heads will bicker, even when in a dire situation.

Since their two heads do not get along and compete with each other for food, they always eat too much. The male Nidoran has developed muscles that freely move its ears in any direction.