The annual Monarch butterfly (Danaus plexippus) migration is one of nature's most fascinating spectacles. Chris Evers, Animal Embassy Director & Founder, took a trip last week to observe this phenomenon in Mexico's central highlands. 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, a migration that spans more than 2,500 miles. The Monarch butterflies spend their winter hibernation clustered in small areas of the Monarch Butterfly Biosphere Reserve (Reserva de la Biosfera Mariposa Monarca), a national protected area and nature preserve that covers more than 200-square-miles.
Adult monarch butterflies have two pairs of brilliant orange-red wings, featuring black veins and white spots along the edges. Males, who possess distinguishing black dots along the veins of their wings, are slightly larger than females. Interestingly, no single individual makes the entire round-trip migration, as butterfly lifespans vary from just two to seven months.
Within the last ten years the population returning to this region in Mexico decreased from an estimated 350 million to an estimated 50 million in the 2012/2013 season. Chris' guide relayed that he has learned that this season (2013/2014) has been the worst on record.
This drastic decrease is partially due to threats monarchs experience during their journey, including the supply of their primary food source - milkweed plants. The supply of this plant has decreased due to herbicides used for agriculture. The butterflies also face extreme weather conditions en route, including higher than normal temperatures and storms - this can affect hatching rates.
Female Monarch butterflies carry as many as 400 eggs. Visitors must tread carefully through the reserve as the effect of stepping on one individual is significant.
Once the Monarch reaches hibernation sites in Mexico, their habitat is threatened by deforestation, illegal logging and at times, disorganized tourism. The Monarch butterfly migration is a significant attraction for visitors to Mexico's highlands and has resulted in a push for ecotourism. If managed well ecotourism can be a great tool in the conservation arsenal. If managed poorly, ecotourism can be to the detriment of a species and its habitat. During the four months of the migration, there is much pressure on the local people to make their living in this short period.
It is daunting to imagine what the next few years will bring for the future of the Monarch butterfly, as well as the plants, animals and people who depend upon them. Hopefully, conservation efforts will continue to progress and pave the way for future successful migrations.