Monarch butterfly numbers dip to second lowest level in Mexico wintering grounds

Experts say the endangered insect numbers fell by 59% this year, blaming pesticide use and climate change for the reduction

The number of endangered monarch butterflies at their wintering areas in Mexico has dropped by 59% this year to the second lowest level since record keeping began, experts said, blaming pesticide use and climate change.

The annual butterfly count doesn't calculate the individual number of butterflies, but rather the number of hectares they cover when they clump together on tree branches in the mountain pine and fir forests west of Mexico City. Monarchs from east of the Rocky Mountains in the US and Canada overwinter there.