Wild Monarch Butterfly Migration and Habitat

Monarch butterfly populations have declined by more than 80 percent in recent decades due to milkweed loss, pesticide use, and habitat destruction along their remarkable multi-generational migration routes across North America.

Key Facts

Monarch butterflies migrate up to 4,500 kilometers between summer breeding grounds and Mexican wintering sites
The migration is accomplished by several successive generations with no individual completing the full round trip
Milkweed is the only plant on which monarchs will lay eggs and caterpillars can survive
Milkweed has declined by 90 percent in some regions due to herbicide use in agricultural fields
The overwintering sites in Mexican mountain forests are critically important and face logging pressure
Western monarch populations have declined from tens of millions to fewer than 30,000 individuals in some counts
Climate change is altering migration timing and increasing the frequency of extreme weather events at key sites

Welfare Considerations

Monarch butterfly welfare intersects complex questions about insect sentience and the scale of suffering experienced by invertebrates during population collapse. Whether individual monarchs experience something analogous to suffering is scientifically uncertain, but the ecological and potentially experiential significance of population decline at this scale warrants serious consideration. The loss of milkweed from agricultural landscapes forces monarch caterpillars to complete development on scattered, often suboptimal plants in road margins and gardens. Extreme weather events that affect overwintering colonies can kill millions of clustered butterflies. Conservation of monarch welfare at the population level requires restoration of milkweed throughout the breeding range, protection of overwintering forest habitat, and reduction of pesticide use in agricultural landscapes that monarchs must traverse during migration.

What You Can Do

Plant native milkweed species appropriate to your region to support breeding monarchs
Avoid pesticide use in your garden during the monarch breeding and migration season
Support the Xerces Society and other organizations working on monarch habitat restoration
Advocate for milkweed restoration in agricultural landscapes through Farm Bill conservation programs
Donate to the protection of overwintering habitat in the Mexican volcanic highlands
Learn which milkweed species are native to your region before planting to avoid non-native varieties