Generations of Migration

Generations of MigrationHere’s a program from our archives. This week, monarch butterflies are beginning their Spring migration from their over-wintering sites on trees in Mexico. The butterflies are heading north and feeding on their favorite plant, the milkweed, during the course of their journey. I’m Jim Metzner, and this is the Pulse of the Planet.You might think of the Monarch butterfly migration as a kind of year long relay race, involving about five generations of butterflies, who reproduce and die along the way, leaving their offspring to carry on. Lincoln Brower, a Research Professor of Biology at Sweet Briar College takes us through this cycle.Brower: So the butterflies that went south now are making a return trip to the US. Most of them get to the Gulf Coast states and there, laid out in front of them, are all these milkweed plants and once they find these milkweeds they just lay their eggs. And then they deteriorate and by probably by the middle of May all of the butterflies that spent the whole winter up in the mountains of Mexico, flew all the way back to the Gulf Coast die. And the offspring, the new generation, hatch out, and these spring butterflies immediately mate and they start laying eggs as they fly north. Milkweeds are sprouting, spring is advancing and they lay their eggs on these milkweeds all the way up to the Great Lakes states.These Monarchs will continue to lay eggs as they fly north. By summertime, they will have died, leaving their children and grandchildren to carry on with the migration.Brower: By the end of the summer, there are just millions of Monarchs all over the place. And then fall has come again and the short day length turns them off and the great-grand kids of the one that flew down the previous fall, head down to exactly the same trees.We’ve been listening to a program from our archives. If you want to hear more, check out our podcast. I’m Jim Metzner.

Generations of Migration

This month marks the start of the Monarch butterflies' migration to Mexico.
Air Date:03/24/2020
Scientist:
Transcript:

Generations of MigrationHere's a program from our archives. This week, monarch butterflies are beginning their Spring migration from their over-wintering sites on trees in Mexico. The butterflies are heading north and feeding on their favorite plant, the milkweed, during the course of their journey. I'm Jim Metzner, and this is the Pulse of the Planet.You might think of the Monarch butterfly migration as a kind of year long relay race, involving about five generations of butterflies, who reproduce and die along the way, leaving their offspring to carry on. Lincoln Brower, a Research Professor of Biology at Sweet Briar College takes us through this cycle.Brower: So the butterflies that went south now are making a return trip to the US. Most of them get to the Gulf Coast states and there, laid out in front of them, are all these milkweed plants and once they find these milkweeds they just lay their eggs. And then they deteriorate and by probably by the middle of May all of the butterflies that spent the whole winter up in the mountains of Mexico, flew all the way back to the Gulf Coast die. And the offspring, the new generation, hatch out, and these spring butterflies immediately mate and they start laying eggs as they fly north. Milkweeds are sprouting, spring is advancing and they lay their eggs on these milkweeds all the way up to the Great Lakes states.These Monarchs will continue to lay eggs as they fly north. By summertime, they will have died, leaving their children and grandchildren to carry on with the migration.Brower: By the end of the summer, there are just millions of Monarchs all over the place. And then fall has come again and the short day length turns them off and the great-grand kids of the one that flew down the previous fall, head down to exactly the same trees.We've been listening to a program from our archives. If you want to hear more, check out our podcast. I'm Jim Metzner.