Monarch Migration
Unlike
most other insects in temperate climates, monarch butterflies cannot survive a long
cold winter. Every fall, North American monarchs fly south to spend the winter at
roosting sites. Monarchs are the only butterflies to make such a long, two-way migration,
flying up to 3000 miles in the fall to reach their winter destination. Amazingly,
they fly in masses to the same winter roosts, often to the exact same trees. Their
migration is more the type we expect from birds or whales than insects. However,
unlike birds and whales, individuals only make the round-trip once. It is their
children’s grandchildren that return south the following fall.
Some other species of Lepidoptera (butterflies and moths) travel long distances,
but they generally go in one direction only, often following food. This one-way
movement is properly called emigration. In tropical lands, butterflies do migrate
back and forth as the seasons change. At the beginning of the dry season, the food
plants shrivel and the butterflies leave to find a moister climate. When the rains
arrive, the food plants grow back and the butterflies return.
To learn more about monarch migration and overwintering sites, and about how scientists
study these phenomena, follow the links below: