Could Raising Captive Monarchs Mess Up Migration?

A late-season male Monarch butterfly nectars on my New York Asters

As you may have heard, alarming new research about raising Monarch butterflies was published recently, by Ayşe Tenger-Trolander, Wei Lu, Michelle Noyes, and Marcus R. Kronforst. Their study found that indoor-reared fifth-generation Monarch butterflies did not display southward flight in tests, which means they wouldn't migrate properly. Uh-oh!

I haven't been able to access the entire article yet, just the abstract linked above, and a write-up in Science. But even those limited sources give me concern about my techniques in raising Monarchs. The researchers raised both commercially-bred monarch caterpillars and wild-caught. Although they used the caterpillar generation that's supposed to migrate, both groups  had neither the elongated wings of migratory individuals, nor showed predominantly southward flight under test conditions. (They attached the mature butterflies to poles in the experiment, so they could observe which directions each butterfly would head. Previous research has shown that in these conditions, migratory monarchs reliably try to fly southward.) The scientists even raised some wild individuals outdoors until the point of pupation, and found that if those individuals eclosed indoors, they too seemed to have lost the tendency to migrate!

Two of my Monarch chrysalids last year, raised indoors & then released after eclosing.

Not unexpectedly, this has thrown the butterfly-raising community into a bit of a tither. Are we actually exacerbating the threats to monarch migration as we try to help? When our efforts include raising the caterpillars indoors, especially the migratory generation, it looks like maybe so.

From what I'm seeing on various email groups, Twitter, and Facebook, many caterpillar hobbyists and citizen scientists are distraught. Should we change our habits and maybe abandon the hobby of raising monarchs?

Honestly, I've already been somewhat concerned about my butterfly raising. This isn't the first study to indicate we might be doing more harm than good, for one thing. I had thought, though, that the main problem was using captive-bred caterpillars, like classrooms might when they mail-order caterpillars from who knows where in order to have them on time for the lesson plan. Since I only raise wild-caught individuals (whether starting as egg or already-hatched caterpillar), I hoped I wasn't doing too much damage.

But another effect of captive-raising caterpillars can be to allow weak genes to survive and get passed along. Since I'm protecting the caterpillars from natural stresses, a trait that would have made an individual less likely to survive isn't actually a problem, and may end up expressed in the next generation too. Especially if I raise every monarch caterpillar I can find, I might still be making my local population less fit. Now this new research just adds more support to reconsidering my actions.

This Monarch caterpillar lived its entire life outdoors at Brookside Gardens, where I found it getting ready to pupate.

I can't speak to what anybody else will or should do, of course, but here are ways I'm planning to change my caterpillar husbandry:

• In general, I will collect and rear no more than 50% of the eggs and/or caterpillars that I find in my garden, of each species. The rest I'll leave wild and unbothered, to fend for themselves. (This also means I'm not reducing the amount of available food for hungry birds!)
• For monarchs in particular, I will rear no more than two caterpillars per generation for the first four generations each year.
• Once the migratory generation's eggs are laid, starting around August in my area, I won't raise any monarchs. 

I also considered trying to create an outdoor setup for raising monarch caterpillars, rather than keeping them in my office indoors. That will take quite a bit more planning, however, so stay tuned.

Another idea was to raise monarchs indoors until they look ready to pupate. Then I could move them outside while they pupate and later eclose. Although I'm not sure exactly what the pupa get from being outdoors, the new research does indicate it's a crucial factor in triggering migration: "In fact, merely eclosing indoors after an otherwise complete lifecycle outdoors was enough to disrupt southern orientation."

I'm not changing how I raise Black Swallowtail caterpillars, or other non-migratory species, as much as I'm changing my treatment of monarchs. I'm definitely reducing how many I raise, going by the 50% rule above. Also, if I find a single egg or caterpillar on any day, I won't bring that in at all. I know I still might be changing something essential in these butterflies by raising them in the protected environment of my office. However, I do call them "pets" sometimes because I know they may not be the same as totally wild individuals. I guess they're kind of half-wild; I do release them as soon as they eclose. I always hope they make my local population larger, going on to mate and lay more eggs that lead to more caterpillars. This summer I'll keep thinking about whether I feel comfortable bringing them inside any more.

As much as I love watching the caterpillars up close, am I being selfish by bringing them inside?

Do you raise butterflies indoors, or have you ever? What do you think about this new research? I'd love to hear your thoughts, whether you plan to stop raising butterflies at all or keep on caring for them like you always have.  Perhaps you even have a totally different method of raising caterpillars than I do. Whatever the case, please leave a comment below to keep the conversation going!