Monarch butterflies bounce back in Mexico wintering grounds

Experts say 35% rise in acreage covered by migratory insects my reflect adaptation to changing climate

Mexican experts have said that 35% more monarch
butterflies arrived this year to spend the winter in mountaintop forests, compared with 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.