The annual Monarch butterfly migration is one of nature's great spectacles and a top attraction for visitors to Mexico. Each year, as many as 60 million to one billion Monarch butterflies make the journey from eastern Canada to the forests of western central Mexico, (more than 2,500 miles). The Monarch butterflies spend their winter hibernation clustered in small areas of the Reserva de la Biosfera Mariposa Monarca (Monarch Butterfly Biosphere Reserve), a national protected area and nature preserve that covers more than 200-square-miles.