"Mexican experts said Monday that 35% more monarch butterflies arrived this year to spend the winter in the country’s mountaintop forests, compared with the previous season.
Experts say the increase may reflect the butterflies’ ability to adapt to more extreme bouts of heat or drought by varying the date when they leave Mexico.
The government Commission for National Protected Areas said the butterflies’ population covered 7 acres this year, compared to 5.2 acres last year.
The annual butterfly count doesn’t calculate the individual number of butterflies, but rather the number of acres they cover when they clump together on tree boughs.
Each year the monarchs return to the United States and Canada on an annual migration that is threatened by deforestation in Mexico’s butterfly reserves and the loss of the milkweed they rely on for food and habitat north of the border."
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