The annual migration of Monarch butterflies to Mexico

The air was still as we made our way on the long uphill hike through the dense forests of Mexico’s Central Highlands. In small clearings pine, oak, and oyamel trees gave way to incredible views over vast untouched mountain ranges.

The small streams that crisscrossed the path began to flicker with signs of life. An orange flash of colour, then another, and another, as sleepy insects haphazardly began taking their first sips of the early morning rainfall.

As we approached the end of the trail, the trees turned tiger-orange with a thick coating of perfectly still monarch butterflies. Still drowsy from the cold mountain night, their intricately patterned wings looked leaf-like as they lay dormant in the boughs and branches of great oyamel fir trees.

As the sun warmed the air, tentative stretches and flutters soon led to mass evacuations of entire branches as they began to take flight, filling the bright clearings in the canopy with a haze of fiery-orange. The sound of a thousand tiny beating wings replaced the still and peaceful silence of this beautiful and remote part of Mexico.

We had travelled by bus from Mexico City to the state of Michoacán, heading out before dawn to arrive at Reserva de la Biósfera Santuario Mariposa Monarca as the day broke. Tours to this natural wonder seemed to be non-existent from the capital city (although it turns out there is one available), so we pieced together our itinerary from conversations in broken Spanish and titbits found on travel forums.

As the hours passed on the long bus journey, the vast suburbs of Mexico City turned to rolling hills. Eventually the conductor (bus driver) came to a halt in what seemed like the middle of nowhere and pointed at us - the only ‘gringos’ on the journey, and asked “mariposa”?  “Si, claro” we answered, and hopped off at what we hoped was the Sierra Chincua Reserve.

One of the greatest natural spectacles in the world

The 2,500-mile migration of the Eastern monarch butterfly is nothing short of heroic. This seemingly inconsequential insect has the longest migration of any, each year making its way from the US and Canada to the Monarch Butterfly Biosphere Reserve in Central Mexico.

Named a World Heritage Site by UNESCO in 2008 the area is closely protected, but in a few areas like the Sierra Chincua Reserve, visitors are permitted to come and witness this truly spectacular marvel.

The Mazahuas and Purepechas people, indigenous to these lands, explain this natural phenomenon as wandering souls coming back to visit loved ones for the Day of the Dead (Dia de los Muertos).

Locals have been coming to witness and celebrate this spectacle for generations, the return of the butterflies also signifies the start of the harvest and these good omens are closely linked to the local culture appearing in art and stories throughout their history.

What time of year do monarch butterflies migrate to Mexico?

The monarch butterflies set off from their northern feeding grounds in August, using air currents to arrive in the early days of November in Mexico. Some have been seen as high as two miles above the ground, but little is known about how high or how far these tiny creatures can actually travel.

For the following four to five months the butterflies overwinter in small and specific patches of the Mexican Central Highlands. The cool mountain forests create the perfect habitat to slow their metabolism and save energy for the return journey in February/March.

This one ‘super’ generation outlives all others, living for around eight months in total. It will take another three to five generations before the annual migration completes its circuit back around the eastern United States and southern Canada.

Just how this generation is able to outlive any other, or how they know exactly where to head for each winter is somewhat of a mystery. The species has been given the scientific name Danaus plexippus, meaning “sleepy transformation” in Greek - perhaps it is this long undisturbed slumber that gives them such longevity.

When is the best time to visit the Monarch Butterfly Reserve?

Though you can spot great numbers of butterflies from November to March, the warmer months between January to February see a lot more activity in the trees.

The butterflies are essentially hibernating but on warm sunny days, even the slightest breeze can dislodge a few hundred or thousand from a branch resulting in a visually magnificent spectacle. 

Where in Mexico do the monarch butterflies migrate to?

Butterflies overwinter in the 129,000-acre Monarch Butterfly Biosphere Reserve. Visit the MBBR from the small mountain town of Angangueo or take a tour from Morelia or Mexico City. It's also possible to take a 3 to 4-hour trip to see the monarch butterflies independently from Mexico City using public transport. You can visit the Cerro Pelon sanctuary inside the reserve.

There are three reserves in the state of Michoacán; El Rosario (the most popular), Sierra Chincua and Senguio. In the nearby state of Estado de Mexico, visitors can also choose between the reserves of Piedra Herrada (near the town of Valle de Bravo), El Capulín and La Mesa.

Risks affecting the Monarch butterfly migration

A major threat facing the Monarch butterflies is agriculture north of the border, the milkweed that the caterpillars feed on has declined rapidly and US citizens have been encouraged to replant this vital plant species.

There has unfortunately been a huge amount of deforestation in Mexico, as well as other factors like pollution and climate change. Though there is some recent positive research that shows the resourceful little monarch butterflies are starting to adapt to change and extreme climate conditions - recorded numbers have slowly started to bounce back.

The charity WWF is working hard to curb the effects of climate change and other factors that are leading to the decline in the numbers of the monarch butterflies. They suggest one way everyone can help is by planting native wildflowers in home gardens and local communities to help feed butterflies and other key pollinators.

Things to know before visiting

• Silence is golden - there are signs and often conservationists working on site to ensure that visitors remain silent when visiting. The butterflies need a peaceful atmosphere to rest.

• Safety - There have been clashes with illegal loggers and conservationists in the state of Michoacán in particular. Tourists are rarely affected.

• Timing is key - If you visit on a warm sunny day you are much more likely to see activity. The sheer number of butterflies is astounding in any case, but allow a few days to make the most of your time here.

• Eco-tourism is working - Though monarchs are widespread throughout the world, this particular species is under threat. Locals and conservationists are fighting to save these protected areas and your visit directly helps.

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