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  • Andy Davis

I asked 14 monarch scientists for their opinions of captive-rearing. Here is what they said

Hello everyone,

As you can see from this blog title, today's entry will be a doozy. I'm once more going to wade into the long-running (ahem) conversation(?) over the practice of captive-rearing monarchs, and whether people should be doing this. This is an often-debated topic, which sometimes gets heated online, and, there has been considerable scientific research into it too. Today I'm going to tell you about a recent survey I did where I asked scientists with expertise on monarchs to weigh in on some of the more controversial points. This survey is not a scientific study, nor is it "published" anywhere but here, so you can take this information in whatever way you choose.

Before I wade in to this, let me first clarify an important point - what is captive-rearing? A lot of people who rear monarchs seem to confuse or conflate the terms captive-rearing with captive-breeding. These terms are sometimes also conflated in journalist pieces around monarchs too, which doesn't help matters. Captive breeding is when captive adult monarchs are allowed to mate in captivity and lay eggs on propagated milkweed. Usually this is only done in commercial (monarch breeding) operations. Captive-rearing refers to anyone who collects wild eggs or larvae from their yards or neighborhoods, and then brings them into captivity (inside or outside) until they metamorphose into adults, and then are set free.

Let me also clarify something else - most of the research around captive-rearing has shown that there are negative consequences for doing this, as harmless as it may seem. Just the simple act of bringing in an egg and rearing it in your house has been shown to interfere with the normal development of monarchs. There is research showing how monarchs reared inside can have impaired navigational senses, how monarchs reared in captivity can be weaker than those from the wild, and there is research showing how captive-reared monarchs have a lower migration success rate than those from the wild. I can also tell you that there is more research on this yet to be published too! Research into WHY this is, is ongoing, but, simply know going forward that this research is all peer-reviewed, and solid. I'm telling you all of this now, because it is important to understand where the opinions of scientists are coming from. We (all of us scientists) read the latest research, or we are the ones conducting it. Either way, we base our opinions on the current science.

Now, let me tell you about my survey. A few weeks ago, I sent out an email to as many scientists that I could think of that currently study, or have studied, monarchs. This amounted to a couple dozen people. I am purposely not going to provide their names here, so that these scientists would remain anonymous. But, know that each of the people I emailed has legitimate expertise on this topic. In my email I asked the group for their assistance in participating in this simple online survey, where they could answer some basic questions about rearing. I also explicitly told them that their answers would remain anonymous - I didn't want anyone to withhold their opinions for fear of being yelled at by someone! Despite this, I still ended up with only 14 people who were willing to provide answers. And, of these 14 scientists, two of them answered "no opinion" on each question. Perhaps this says something about the controversy around this topic... But, I am confident that the people that did answer the questions were legit experts on this topic. And the fact that there were 12 experts who provided answers means that this should be taken as the "majority" opinion among researchers.

Anyway, the survey was intended to solicit feedback on a couple of key questions that have circulated for some time around this topic. One of the biggest questions we all have, is how many monarchs are "SAFE" to rear, and conversely, how many is "TOO MUCH?" These questions are becoming more and more critical since this fad has continued to grow.

OK, so next, I'll list each question, and then the responses from the scientists.

The first question was simply a test to see if I was talking to the right people - Are you a scientist who studies (or has studied) monarchs? All 14 people answered yes.

Second question - About how many monarchs would you say is "safe" for the average homeowner to rear in captivity (per year)? Safe here is defined as not harming the overall population, and, keeping in mind that there are thousands of citizens involved in rearing

Here, participants could select numbers from 0 to 100, or an "unlimited" option. The answers here ranged, but I think there is a little consensus. Of the 12 people who provided an opinion, 10 (83%) of them selected numbers between 0 and 40. Two people selected 100. If you average the entire 12 numbers, you get 29.5. So it looks like the answer to this question (i.e. how many monarchs do experts think is safe to rear per year?), is about 30.

The third question was the flip side of the second question - How many is "too many" to rear (i.e. unsafe for the population) by homeowners per year?

Again, participants could choose from a range of answers, from 10 to 1000, or even "more than 1000." The answers to this question were much more scattered, which may reflect the fact that we don't really have a lot of information to go on for this. People selected 10, 20, 30, 50, 100, 200 and even 1000. If you average all of them, you get 149. So, it looks like you could say that the experts were divided on this question, but a good benchmark is about 150 monarchs - that's about how many we think are "too many."

On the last question there was very little doubt as to what the majority opinion was, and here the question was designed to get to the heart of the matter, with no ambiguity or wiggle room. The question was - In your opinion, does captive-rearing help the monarch population? The answer options were simply yes or no, with an option to answer "no opinion", which 2 people selected.

Of the 12 people who answered, 11 (92%) answered NO. One person selected YES.

So in other words, 92% of monarch scientists are of the opinion that captive-rearing does not help the monarch population. That's a pretty solid majority.

That was the end of the survey. Now let me discuss what comes next - the inevitable arguing over these results.

At this point, you may be saying, why do most scientists believe rearing doesn't help? Well, I already answered that question above - because of the latest research and data. We scientists tend to form opinions on what the data show, since it's kind of our job to be objective. Thus far, we have a number of studies that are all pointing to the same thing, that captive-rearing produces monarchs that are not as good as their wild counterparts. Thus, it seems clear from these data that adding inferior monarchs to the population would not help the population. Yes, you are saving those inferior monarchs from their certain demise in your backyard, but is it helping the population to allow them to survive? That's the real question.

In these arguments, some people who rear monarchs will usually point out that they have had one or more monarchs that "made it to Mexico," and they argue that this means the scientists are all wrong, and that these monarchs are just as good. This is a misinterpretation of the research, and a gross oversimplification. The research around monarch migration ability shows that captive reared monarchs have reduced success, not that they are never successful - see the difference? In fact it's the same with most of the traits that have been measured thus far, including wing size, navigational ability, strength, etc. And, of the people who point out that one of their reared monarchs made it, how many did they have to release over the years to get that one recovery? A thousand, five thousand? Get them to do the math. For wild monarchs, tag recovery rates are about 1 in 100. I bet they don't have a rate as good as that, which proves my point. The point is that even though one of your or your friend's monarchs made it, you still released a lot of inferior monarchs into the population. What impact did those monarchs have? Were they carrying diseases, did they have reduced immune defense, was their metabolic rate what is should be? People really need to be thinking of the bigger picture here, and think of the population.

Let me end this post with some advice to the critical-thinking blog readers here. I'm sure that with a topic like this one, you will no doubt share this post among your favorite monarch facebook groups, which are probably composed mostly (if not entirely) of people who captive-rear monarchs! This is welcome, since this information does need to be shared widely. However, let me caution you on the feedback you will get. You will probably get a lot of responses from a lot of people who already participate in this activity, and who don't want anyone telling them to curtail it. If you share this post, hoping that someone will provide a counter-argument, you will likely get one, but, is that person an expert? I'm sure they think they are, and they will no doubt tell you they are. This is the real problem with facebook groups - these are basically just echo-chambers, and this is true in the monarch rearing groups, as well as others, like antivaccine groups. So keep in mind who you are getting your information from. If you want to know the opinions of experts on this topic, this is it.

That's all for now folks.


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The science of monarch butterflies

A blog about monarchs, written by a monarch scientist, for people who love monarchs

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