Each fall, in a spectacular flurry of orange and black, the monarch butterflies of eastern North America migrate south to spend the winter in a small, mountainous region in Mexico.

Temperature is the signal that tells them to return to the U.S in the spring, so as the climate changes, the king of the butterflies may be at risk.

Some monarchs may already be responding to changing conditions. More are now spending the winter along the Texas Gulf Coast, where they’re finding a more suitable climate and a new year-round source of milkweed, as a tropical variety gains popularity with gardeners.

These monarchs are now breeding throughout the winter, so there’s concern that a random cold snap could kill their eggs and larvae. But Kelly Nail of the University of Minnesota says that’s unlikely.

Nail: “I’ve found that the immature monarchs can actually withstand a lot cooler temperatures than we thought.”

Her research indicates that as the climate warms, some monarchs may be able to adapt by shifting their ranges further north. But Nail cautions that non-migrating butterflies are more susceptible to disease, so the future of this iconic species remains uncertain.

This segment of Climate Connections was produced in partnership with I See Change.

Reporting credit: ChavoBart Digital Media and iSeeChange.
Photo: Monarch butterfly feeding from milkweed plant (copyright protected).

More Resources
Monarch butterly migration
Monarchs in a Changing World
Citizen science observations of monarch butterfly overwintering in the southern U.S.
Cold tolerance of immature monarchs