The Dplex-L List is Monarch Watch's monarch butterfly discussion list.
Monarch Watch Conservation Specialist, Debbie Jackson asked that we post this to hopefully allay fears of those that are rearing/raising eggs or caterpillars from the wild.
This is in response to the recent study outlined in an article from The Atlantic, " Monarch Butterflies Reared in Captivity Lack a Crucial Ability"
From: Karen Oberhauser
Date: Wed, Jun 26, 2019 at 3:44 PM
Subject: [Dplex-L] Commercial and Indoor rearing
Dear All,
I'm going to add my thoughts to a long line of communication on the recent paper in PNAS about commercial and indoor monarch rearing and the resulting coverage. I was interviewed for several of the media reports on this article, and have thus received many messages about my message, at least as it was conveyed by reporters.
The most important finding of the paper in question is that monarchs reared in captivity for generation after generation become genetically distinct from wild populations, and at least in the commercial butterflies purchased for this study, did not exhibit migratory behavior. That is a problem, and a robust result of the paper. The fact that only one commercial stock was used means that the study needs follow-up, but it does show that long-term mass rearing can result in genetic change that has the potential to cause problems for individual monarchs that are then released into the wild, and potentially for wild monarch populations if there is interbreeding.
Large-scale mass rearing for multiple generations is very different from rearing monarchs in captivity that are collected as eggs or larvae, and then released when they emerge as adults. It is important to note that the inside rearing in the experiment was done in incubators in which temperature and light were carefully controlled; think of a big warm refrigerator with controlled lights. As a result, the monarchs were not exposed to any natural light or temperature fluctuations; the lights went on for 14 hours, and were then off for 10 hours. While the authors said that these are fall-like conditions, they aren't. In the fall, daylength outside is changing rapidly. Work done in my lab at the University of Minnesota showed that decreasing daylength was a key driver of diapause induction. In most inside rearing conditions, such as in people's houses and classrooms, there are windows and diurnal temperature fluctuations which provide exposure to natural environmental cues. I’m actually not surprised that the monarchs didn’t migrate after being in an incubator under constant daylength conditions.
The genetic aspects of the study were interesting and important, but the conclusion about risks of single-generation raising of wild-collected eggs and larvae has much less validity. In my opinion, what people are doing when they rear monarchs in this way has incredible educational, inspirational, and scientific importance. As Ilse Gebhart pointed out, we would not know what we know about monarch parasitoids without the citizen scientists who rear monarchs they collect as eggs and larvae. I would encourage everyone who does rear monarchs to report their findings to the Monarch Larva Monitoring Project (mlmp.org; look for Activity 3 in the monitoring section).
The key message from this study is that there is strong evidence that purchasing monarchs from commercial suppliers will not help monarchs, and it could cause harm to release those monarchs into the wild. In my opinion, the risks of commercial production outweigh the benefits. I have said that often, and this study provides documentation of one of the potential risks, genetic change that makes the monarchs less successful in the wild.
Thanks to everyone on this list for your clear dedication to monarch conservation, which I share.
Karen
