Hundreds of Monarch butterflies arrive in the forests of Mexico the first days of November. Historically, they are emblematic and iconic to Mexico.
The Monarch butterflies begin their flight in August and September, from southern Canada and the northern United States, and arrive in Mexican territory in the month of October. They travel more than 4500 kilometers and their journey takes about three months.
The southward journey of the Monarch butterflies takes them through the Mexican states of Coahuila, Nuevo Leon, Tamaulipas, Zacatecas, Queretaro, Aguascalientes, Guanajuato, San Luis Potosi and Hidalgo. There are high concentrations of monarchs in this migratory flyway corridor through these Mexican states.
At the beginning of November, Monarch butterflies arrive in the oyamel fir pine biosphere forests in the states of Mexico and Michoacan (The Monarch Butterfly Biosphere Reserve). to hibernate in the warmer climate. Here they cluster in groups on tree branches to form large colonies and protect themselves from the cold.
Since butterflies are insects, they are cold blooded, and their temperature adapts accordingly. As it warms up during the day, they can be observed in flight, drinking water and nectar, and mating.
Origin of Monarch Butterflies
Monarch butterfly (Danaus plexippus Linneo) is historically endemic to North America, native to North America and South America. Monarchs in North America have coevolved and depend on native milkweed species during their complete life cycle. They are no longer found in South America but have spread to other places in the world, with suitable feeding and breeding habitats. Historically, they are a species emblematic to Mexico, and feed on nectar from a wide range of blooming native plants, including milkweed.
Monarch butterflies are naturally colorful with patterns and their distinctive deep orange colors (black border and white spots) are poisonous to predators. As Monarchs feed, they Milkweed produces glycoside toxins to deter animals from eating them, but monarchs have evolved immunity to these toxins. As they feed, monarch caterpillars store up the toxins in their body, making them taste bad, which in turn deters their predators. The toxins remain in their system even after metamorphosis, protecting them as adult butterflies as well.
Monarch butterflies weigh barely half a gram, and their wingspan can reach five centimeters in length. Distinct features include their ability to adjust their temperature, allowing them to conserve a great amount of energy. They also possess a sophisticated navigation system that uses the Earth’s magnetic field to guide their internal magnetic compass; and a “sun” compass, piloted by the height of the sun and rays of sunlight. Monarchs also have a special gene, in which powerful muscles give them an advantage during flight. They can perceive humidity in dry climates.
Monarchs are well known pollinators, an iconic pollinator species. They pollinate many types of wildflowers.
Furthermore, if they emerge in the spring, they reproduce in days. If they are born in late summer or fall, they head south for a warmer climate. These monarchs make their annual migration south.
Lastly, the life cycle of Monarchs makes them resistant. The generation that is born in late summer and early fall can live nine months (12 times more than other butterflies). These are born to complete a lengthy migration.
Monarch Butterfly Conservation in Mexico
Monarchs are critically in danger. Milkweed is not as readily available and much of the climate has changed to their disadvantage. Many are killed en route south. Monarch sanctuaries have been established to protect winter habitats and there are five biospheres in Mexico where Monarchs are protected, called the Monarch Butterfly Biosphere Reserve.
The Monarch Butterfly Biosphere Reserve is a recognized UNESCO World Heritage Site.
Recommendations when visiting a Monarch Butterfly Sanctuary
1. Follow the instructions of the tour guides.
2. During the visit, walk only among the established trails.
3. Do not introduce food, alcoholic beverages, sharp objects, weapons or pets.
4. Do not take any plants, animals, mushrooms or any other element that is a part of the forest.
5. No smoking / No campfires.
6. Respect the limits of access during the observation of the butterfly colonies.
7. Remain silent druing your stay.
8. Do not use flash to take photographs
9. Do not bother, trap or capture the butterflies.
10. Stay only 18 minutes within the Sanctuary so that others may have the opportunity to visit, such as to not alter the state of hibernation of the Monarchs.
During the five-month stay in Mexico, the Monarch butterflies establish their colonies. Their flight movements increase as the days get longer in preparation for their flight north.
February is the month they prepare for their journey north. They begin to head north and continue to fly. They stop en route to lay eggs. The new generation continues further north and lays eggs. Four or five generations of Monarch butterflies may continue before reaching Canada.
Government of Mexico SEMARNAT