Mexican experts said Monday that 35% more monarch butterflies arrived this year to spend the winter in mountaintop forests, compared to the previous season.
Experts say the rise 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 natural protected areas said the butterflies’ population covered 2.84 hectares (7 acres) this year, compared to 2.1 hectares (5.2 acres) last year.
The annual butterfly count doesn’t calculate the individual number of butterflies, but . . .