Monarchs on the wing: Mexico's butterfly biosphere reserve turns orange

One of the planet's most spectacular natural events is nearing its peak: after a journey of more than 4,000 kilometers from Canada and the United States, monarch butterflies are arriving in the mountain forests of central Mexico. According to Mexico's protected areas agency Conanp, the colonies settle between late October and early November, a period that coincides with the Day of the Dead on Nov. 1 and 2. On Oct. 25, local media reported butterflies in Nahuatzen (Michoacán) and in the state of Guanajuato, about 80 kilometers from the wintering grounds.

The Monarch Butterfly Biosphere Reserve covers 56,259 hectares about 100 kilometers northwest of Mexico City, on the border between Michoacán and the State of Mexico. According to UNESCO, between millions and up to about a billion butterflies overwinter there; the reserve protects 8 of the 14 overwintering colonies and an estimated 70 percent of the overwintering butterflies of the eastern population. The insects gather in dense clusters on the trunks of oyamel firs and can turn whole stretches of forest orange.

Arrival does not yet mean the sanctuaries are open: according to Conanp, the butterflies settle in gradually during November. The official opening of the visitor season has been announced for Friday, Nov. 20, 2026, El Congresista reported, citing the reserve administration. Well-known viewing sites include El Rosario (Ocampo) and Sierra Chincua (Angangueo). According to La Voz de Michoacán, the butterflies become more active in February and March before starting their journey back north.