..how some Monarch butterflies live longer than others? (with Isis Howard)

Ever Wonder? / April 10, 2024
Image attribution
Courtesy of Isis Howard
Image attribution
Courtesy of Isis Howard

In an earlier episode, we chatted with Isis Howard, who works at the Xerces Society for Invertebrate Conservation.  She told us about the multi-generational migration of Monarchs across 3 different countries. Here she further explains why some monarchs live a few weeks, while other monarchs live 6 to 9 months! 

Ever Wonder... how some Monarch butterflies live longer than others? 

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Karen Arroyo (00:06):

Hello, this is Ever Wonder? from the California Science Center. I'm Karen Arroyo. In an earlier episode, I spoke with Isis Howard, who works at the Xerces Society for Invertebrate Conservation. Isis tells us about the multi-generational migration of monarchs across three different countries. She also explains why some monarchs live for a few weeks, while other monarchs live for six to nine months. Ever wonder how some monarchs live longer than others. In this episode, Isis explains how many generations of monarchs typically takes to travel from Canada to Central Mexico, and why some monarchs lifespan can vary so much. Let's take a listen.

Karen Arroyo (00:43):

But one last question that I really do wanna talk about and touch on is the multi-generational migration of monarchs. So I know that they travel throughout three different countries, Canada, the U.S, And of course Mexico, but they do this across multiple generations. So the same butterfly, the same monarch that starts the migration, doesn't end the migration. So can you tell me a little bit about how many generations it takes to complete a migration and their typical lifespan?

Isis Howard (01:10):

This is a great question. There are several generations of monarch butterflies that contribute to this epic migration or journey from their breeding sites to their overwintering habitat. Now, the typical monarchs that we see in spring, summer, and fall visiting our communities and sipping nectar, those are, those butterflies are only going to live, um, a few weeks. But the migratory butterflies or the butterflies that are traveling down to their overwintering sites in Mexico or along the coast of California and Baja California, those butterflies can actually live six to nine months versus the two to five weeks of earlier generations. This is really incredible. And the reason that's possible is because they enter a state of diapause and it's not the same, but you can kind of think about it like how bears will go into their caves and hibernate for winter and their metabolisms kind of shut down and they're sleeping a lot. Um, I'm not a bear biologist, so apologies, bear biologist if I'm getting anything wrong, but that's like something that everyday people can kind of relate this to. So these traveling or migrating butterflies are entering the state of reproductive diapause where they're no longer going to put their metabolic energy into creating new life and success of generations. Instead, they're focusing their energy on traveling to their safe overwintering sites, which protect them from winter weather, um, storms like that, and they're going to kind of shut down their metabolism and rest. So by shutting down or slowing down, they are allowing themselves to preserve their energy so that they can remain alive for months rather than weeks. And then in the early spring, they'll start that initial migration out and get to that early season milkweed and start reproducing and creating that next generation.

Karen Arroyo (03:27):

So by going into reproductive diapause, it's almost like they can extend their lifespan simply by not reproducing.

Isis Howard (03:35):

Yeah. And so, you know, you might see two or three migrations northward up to the breeding sites and two or three migrations, you know, southward towards the overwintering sites. And a little known thing is that, you know, scientists, we haven't quite figured out how monarchs are locating the same overwintering sites year after year. It's one of those mysteries that is pretty stunning.

Karen Arroyo (04:03):

I think that is the first thing that got me interested in researching Monarchs specifically. I mean, I've, of course, I've always been surrounded by them, not just culturally, but physically. And as soon as I heard that monarchs always migrate back to the same forest, down to the same tree where they overwinter and how they have the ability to do that is still unknown to a lot of scientists. It's definitely what got me into studying monarchs. But the fact that they have almost this inherited ancestral memory or just knowledge that helps guide them back to the, to the same spot every single year, generation across generation across generation is breathtaking.

Isis Howard (04:43):

Monarchs are incredible.

Karen Arroyo (04:45):

They're incredible.

Karen Arroyo (04:48):

And that's our show. Thanks for listening. Until next time, keep wondering. Ever Wonder? from the California Science Center is produced by me, Karen Arroyo, along with Perry Roth-Johnson, D Hunter White, and Jennifer Aguirre. D Hunter White and Liz Roth-Johnson are our editors. Music provided by Michael Nickolas and Pond5. We'll drop a new episode every other Wednesday. If you're a fan of the show, be sure to subscribe and leave us a rating or review on Apple Podcasts. It really helps other people discover our show, have a question you've been wondering about. Send us an email or a voice recording to [email protected] to tell us what you'd like to hear in future episodes?