Every autumn, millions of monarch butterflies fly thousands of kilometres from Canada and the United States to spend the winter in the fir and pine forests of central Mexico. Cerro Altamirano, near the village of Contepec in the state of Michoacán, is one of the mountains where they gather, part of the Monarch Butterfly Biosphere Reserve, a UNESCO World Heritage Site. When the butterflies are here, roughly from November to March, the branches of the trees are covered with them, so thickly that they sag under the weight.
The arrival of the monarchs coincides with the Day of the Dead at the start of November, and in local tradition the butterflies are linked to the souls of the dead returning. The phenomenon is one of the great spectacles of nature. On sunny days, as the air warms, the butterflies take to the air in clouds, filling the forest with the soft sound of their wings. Sanctuaries are open to visitors in the season, usually with local guides, and the walk up through the forest at altitude can be tiring, so go slowly.
The riding in this part of Michoacán and the neighbouring State of Mexico is mountainous and varied. Roads climb through forests and farmland, with sharp bends, steep grades and occasionally poor surfaces, potholes and topes, the speed bumps that appear without warning in every village. Traffic includes trucks, buses and livestock. The altitude, over 2,500 metres in places, means cool mornings and evenings even in the dry season, and afternoon storms are common in summer. The best riding weather, and the butterfly season, is the dry winter months.
Contepec is a small town with basic services, and Temascalcingo and Maravatío, larger towns nearby, have fuel and more choice. Local food is hearty: corundas, triangular tamales from Michoacán, and carnitas, slow-cooked pork. In the sanctuaries, follow the guides' rules: stay on the paths, keep quiet and do not touch the butterflies. Arriving in the late morning on a sunny day gives the best chance of seeing them in flight, and the sight of the forest coming alive with orange wings is unforgettable.