Experts in Mexico said yesterday there is a tentative sign of hope for the mass migration of monarch butterflies, whose numbers dropped to their lowest level ever last year. The head of Mexico's nature reserves, Luis Fueyo, said the first butterflies have been seen entering Mexico earlier than usual this year. Fueyo said it is too early to say whether butterfly numbers will rebound this year from a series of sharp drops, but noted "this premature presence could be the prelude to an increase in the migration." He said the first butterflies have been sighted in the northern border state of Coahuila. Most normally arrive in October from the United States and Canada, where they spend the summer. "This year, we are seeing them present in Mexican territory earlier than usual," Fueyo said.
By November they settle in mountaintop forests where they spend the winter. Fueyo said authorities will wait to make a definitive count after the butterflies have settled in completely, something that usually occurs by December. Mexico, the US, and Canada are working to create a corridor of milkweed-friendly areas along the three-nation migratory route. The butterfly has to reproduce along the way, and lay eggs on milkweed leaves; their decline is being driven by genetically engineered, herbicide-resistant crops that have drastically cut the amount of milkweed. Last year, monarchs covered only 1.65 acres in the forests west of Mexico City, down from more than 44.5 acres at their peak in 1996.