Monarchs migrate each autumn from Canada and the US but climate swings delay their migration and illegal logging threatens their habitat.
Extreme climate swings in North America pose a threat to the annual migration pattern of monarch butterflies.
Monarchs migrate each fall from Canada and the United States to the bordering area between Michoacan and the state of Mexico.
They depend on environmental cues (temperature in particular) to trigger reproduction, migration, and hibernation, the World Wildlife Fund (WWF) says.
"Because of global warming, because of all these changes to the climate that we are getting because of human activities, what we have seen is that the winters are extremely cold and we have storms that can kill many of these animals," ecologist Gerardo Ceballos says.
Illegal logging in the butterfly reserve and pesticides along the insects' flight path also threaten their habitat.
The WWF's 2013 report from Mexico shows the number of monarch butterflies wintering there was at its lowest in 20 years.
Scientists say with each passing year, a delay in their migration time is becoming lengthier.
TRT World’s Alasdair Baverstock reports from Michoacan.