Air Date: Week of March 12, 1999

This week, facts about... the annual migration of Monarch butterflies -- millions of them.

Transcript

CURWOOD: In March, not all the madness is on the basketball court. This month millions of Monarch butterflies begin their annual migration. While many butterfly species migrate, only the Monarchs return to the same wintering site each year. Some like to roost on eucalyptus or cypress trees on the Southern California coast, but most Monarchs slumber through winter in the mountains of central Mexico. Colonies there were smaller this year in part because logging reduced butterfly habitat. Still, come spring, the regal butterflies head north and stop where they find milkweed. Then they lay their eggs and die. But in a week or so, their offspring continue the journey north before they, too, stop, lay eggs, and perish. And so on, and so on. It can take as many as 4 generations to complete the 5-month journey north. The Monarchs who winter in Mexico fly over Gulf Coast states and head north, arriving in eastern Canada in late summer. The California Monarchs follow the west coast up to British Columbia. Then, early in the fall, clouds of Monarchs head south, retracing the path of thousands of miles that their parents, grandparents, and great-grandparents flew over only months before. And for this week, that's the Living on Earth Almanac.