ValuesThe Monarch Butterfly Biosphere Reserve World Heritage property protects key overwintering sites for the monarch butterfly. Criterion (vii): The overwintering concentration of the monarch butterfly in the property is the most dramatic manifestation of the phenomenon of insect migration. The property protects 8 of these colonies and an estimated 70% of the total overwintering population of the monarch butterfly’s eastern population. IntegrityThe property includes more than half of the overwintering colonies of the monarch butterfly’s eastern population. Due to its migratory nature, the maintenance of the overwintering phenomenon also requires attention to the conservation of the monarch butterfly by those countries through which it travels during its life cycle.