The Poison that Protects

MONARCHS – MilkweedHere’s a program from our archives. This is migration season for millions of Monarch butterflies making their way north from their over-wintering sites in Mexico. Along the way, they’re feeding on milkweed, a plant that both nourishes the Monarchs and protects them from most of their predators. I’m Jim Metzner, and this is the Pulse of the Planet.Brower: It turns out that not very many insects actually can feed on milkweeds because they’re extremely toxic plants. Lincoln Brower is a Research Professor of Biology at Sweet Briar College.Brower: If a bird eats a Monarch butterfly that is fed on a milkweed plant, the bird within about twelve minutes will be bending over and throwing up like crazy. And then they remember the color pattern of the Monarch, then the next time they encounter a monarch, they won’t touch it. And one of the reasons Monarchs are probably so successful in terms of their numbers and their survival in Mexico is because they are so highly toxic. Birds learn no, don’t eat Monarchs. They’re going to make me sick. And it turns out there are two species of birds that have overcome the chemical defense of the Monarch. One is an oriole. And their tongue is like a whisk and they actually spear a monarch, open the beak and use that tongue to whisk out the insides. But they only eat the Monarchs that are not toxic. They can taste the toxicity because it’s bitter. And then there’s another species of bird which is related to the rose breasted grosbeak and these grosbeaks actually able to tolerate high doses of toxin. And they simply chomp the abdomens off and eat the whole abdomen. So these two species of birds are eating up to maybe ten percent of the Monarchs in the colony.We’ve been listening to a program from our archives. If you want to hear more, check out our podcast. I’m Jim Metzner and this is the Pulse of the Planet.

The Poison that Protects

The Monarch butterfly's life cycle depends on a plant that's highly toxic to many animals.
Air Date:03/25/2020
Scientist:
Transcript:

MONARCHS - MilkweedHere's a program from our archives. This is migration season for millions of Monarch butterflies making their way north from their over-wintering sites in Mexico. Along the way, they're feeding on milkweed, a plant that both nourishes the Monarchs and protects them from most of their predators. I'm Jim Metzner, and this is the Pulse of the Planet.Brower: It turns out that not very many insects actually can feed on milkweeds because they're extremely toxic plants. Lincoln Brower is a Research Professor of Biology at Sweet Briar College.Brower: If a bird eats a Monarch butterfly that is fed on a milkweed plant, the bird within about twelve minutes will be bending over and throwing up like crazy. And then they remember the color pattern of the Monarch, then the next time they encounter a monarch, they won't touch it. And one of the reasons Monarchs are probably so successful in terms of their numbers and their survival in Mexico is because they are so highly toxic. Birds learn no, don't eat Monarchs. They're going to make me sick. And it turns out there are two species of birds that have overcome the chemical defense of the Monarch. One is an oriole. And their tongue is like a whisk and they actually spear a monarch, open the beak and use that tongue to whisk out the insides. But they only eat the Monarchs that are not toxic. They can taste the toxicity because it's bitter. And then there's another species of bird which is related to the rose breasted grosbeak and these grosbeaks actually able to tolerate high doses of toxin. And they simply chomp the abdomens off and eat the whole abdomen. So these two species of birds are eating up to maybe ten percent of the Monarchs in the colony.We've been listening to a program from our archives. If you want to hear more, check out our podcast. I'm Jim Metzner and this is the Pulse of the Planet.