Brief Note: Monarch Caterpillars Still Fine

Getting large now, actually. I expect three of them to slink off to pupate any day now, with the rest not far behind. It always amazes me how much they can eat – and how much of the milkweed itself they can eat, all the way back to fairly thick main stems. Incidentally taking out any flowers or seedpods in the process.

Which leads me to wonder if part of the monarch population problem is one of scale. Sure, a couple milkweed plants can get razed back to bare stems by hungry caterpillars and survive – but they won’t produce seeds. So for the long-term survival of monarchs, you don’t just need enough milkweed to feed caterpillars. You need enough that they can’t eat all of it.

This could be tricky. Every time we’ve had milkweed planted, at least one butterfly has found it – and just one will lay more than enough eggs to munch the whole plant. So you need more milkweed than can readily grow in a few pots… or you need some wasp nests nearby to munch enough of the caterpillars that the survivors leave a few flowers to become seedpods. Which might seem to contradict the goal of “more monarch butterflies” – but if the milkweed can’t survive and spread, then in the long term there will be fewer monarchs.

You have to look at available resources, and how they can be best managed for your ultimate goals. Sure, you can hope to have a really good year… but hope is not a plan.

It’s still February, we could still have a freeze. We’ll see what happens.

9 thoughts on “Brief Note: Monarch Caterpillars Still Fine

  1. I wonder if the effect of the caterpillars might be magnified by a few things – the milkweed is growing in a pot, and from what you’ve mentioned, the plants are overwintering fine but are probably not in rapid growth either. Not sure what species of milkweed you have, but the most common native milkweed in my region has rhizomes, so naturally grows in clumps and colonies. Under those conditions, it doesn’t really matter if some stems get denuded; at least one shoot is likely to set seed. It also probably helps that the flowering period here begins slightly before the Monarchs lay eggs, so the seeds are already developing when the caterpillars really get ravenous.

    Liked by 1 person

  2. Whenever I start thinking about sustainable populations I just end up amazed that we have ecology at all.

    Which is why I’m not hugely enthusiastic about the talk about bringing back extinct species.
    Yes, humanity is killing off a lot of things we probably shouldn’t, but if we forcefully keep all species alive, that’s just as weird from an ecological perspective as killing them.

    Liked by 2 people

      1. I see no difference in bringing back stuff than from breeding new stuff, so if it’s cool and doesn’t involve immoral behavior*, go for the cool!

        *say, the occasional “bring back Neanderthals” would functionally be maiming a human being for genetic traits of one group of ancestor; a contrasting example is bringing back the wooly mammoth, which would be painlessly altering an elephant for genetic traits of a related species

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  3. Don’t think we get Monarch’s in my area, but it can be very frustrating to try and grow something the wildlife keeps munching on. At least the caterpillars need the milkweed. Maybe if you staggered the planting period? It’s what they recommend for having a continuous harvest of vegetables, give me a bit and I’ll remember the actual word…

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