UPDATE: Winter Monarch Butterflies are Reproducing at the Museum Reach Milkweed Patch on the San Antonio River Walk

Graduate student Kelly Nail was pleasantly surprised at the bounty of butterfly life unfolding at the Museum Reach milkweed patch on the San Antonio River Walk just this week.  The patch of milkweed, a Monarch butterfly host plant, was planted two years ago as part of the City’s redevelopment of the former drainage ditch and lies just a five-minute walk south of the Pearl development on lower Broadway.

Kelly Nail, Graduate Student, Univeristy of Minnesota

Kelly Nail, Graduate Student, Univeristy of Minnesota

Nail majored in mathematics and biology at St. Olaf College.  After teaching high school biology in rural Mississippi, she returned to school to study Monarch butterflies.  Her dissertation, overseen by renown Monarch butterfly scientist Dr. Karen Oberhauser at the University of Minnesota, will explore the effect of climate change on Monarch butterflies.  Nail flew to Houston this week to talk to Monarch citizen scientists about “winter Monarchs,” then made the three-hour drive to San Antonio to see how Alamo City butterflies are faring.

The Museum Reach milkweed patch did not disappoint.

We observed several Monarchs flying, more than a dozen Monarch caterpillars and one Queen caterpillar in various stages of development, dozens of chrysalises–spent, interupted, and in process–and one egg.  We also saw instances of the brilliant-but-creepy tachinid fly.  This parasitoid lays eggs on Monarch caterpillars, which kills them when the flies feed on their living bodies and eventually hatching just before the Monarchs pupate, leaving a caterpillar corpse in their wake.  Scientists suspect that Monarchs born later in the season and further south are more likely to encounter such a fate.

Nail was delighted to find such a jackpot of Monarch data. “I was impressed to see all stages of the life cycle in one single place,” said Nail.  “And right along the River Walk in the middle of San Antonio.  It’s pretty amazing.”

One of the questions she hopes to answer:  Are “winter Monarchs” reproductive?  Judging from this field trip–no doubt about it.

Butterfly fans and those of us who tag Monarch butterflies in the fall have always been told that late season Monarchs do not reproduce and are behaviorally and biologically different from spring and summer Monarchs.  Supposedly, late season Monarchs remain sexually inactive, saving their energy for the great migration to Mexico.  There, they wait out the winter and emerge from their diapause in the spring to partake in an orgy of butterfly mating in the mountains of Michoacan, often laying their first eggs on Texas milkweeds in March or April.

Butterfly fans know that local populations of Monarch butterflies can establish themselves when host and nectar plants are available and the weather cooperates.  We see it in Houston, Florida, and now–San Antonio.

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Based on personal observation and discussions with professional butterfly breeders, it appears that Monarchs are just like us:  opportunists.  With ripe conditions and mates available, they’ll pounce on the chance to reproduce.

Our local Monarchs are likely to continue their procreative antics as long as  temperatures remain above freezing and milkweed and nectar plants provide host and sustenance.  San Antonio’s Museum Reach milkweed patch,  semi-protected from the elements with supplementary grey water and temperatures more moderate than street level, is destined to become a favored nectar and host plant hangout where Monarch butterflies gather to find partners.   That’s good news for those of us who hope to enjoy butterflies year-round.

We look forward to Nail’s research and to more visits to the milkweed patch.

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23 Responses to UPDATE: Winter Monarch Butterflies are Reproducing at the Museum Reach Milkweed Patch on the San Antonio River Walk

  1. Mary Kennedy says:

    Hi Monica,
    Do we have anyone monitoring the Museum Reach milkweed each week and sending data to MLMP?

    Mary Kennedy

  2. Monika Maeckle says:

    Mary, I monitor pretty regularly but haven’t been officially reporting anything. Let me know how I can help!

  3. Dr. Danny says:

    The reproductive late season monarchs are the exception, not the rule. There are too many exceptions to list on websites and if they were listed, it would begin to overwhelm many. Also, its not the day that they were born that changes them, its “The shorter days and cooler air” that triggers changes (which is relative to latitude). Near cities, the amount of light is much higher (shorter days may be less able to be detected). Near cities, the overall temperature is generally higher (cooler air may be less able to be detected). In Texas, and other lower lattitudes, its often hard to tell there is winter.

    To prevent some misinterpretation… One should not think that scientists “dont know” about these populations even though butterfly fans know it. Certain interpretations of such words could lead to a divide between scientists and citizens; this is surely not the goal. Also, i’m sure it could be found in Mississippi, Alabama, Georgia, California, and many more locations

    Also, I would definitely agree that “monarchs are opportunistic” but this applies at the individual organism level; everything is (i’ve seen grasshoppers eating dead honeybees!). The monarch species (sum/average of all individuals) is unlikely to be opportunistic and switch to winter reproduction any time soon. Monarchwatch.org lists the general monarch SPECIES strategy, while some monarch INDIVIDUALS may choose different strategies. Such variant strategies, present in all species, is the food for evolutionary change. If these late reproductives survive, their genes will be more present in the coming generations. When hard freezes hit and serious winters come, they die and much of their genetic predispositions. If global warming continues, they might be much more useful strategies. So we should definitely keep an eye on them.

    Just trying to add some more objectivity in places where I saw that it might be needed when some interpretations could lead a few the wrong way, even though this was likely not the expected interpretation that the AWESOME Monika Maeckle wanted. I’m quite happy to this blog continues, it surely is a gem. Sorry for the long post Monika!

    • Monika Maeckle says:

      Thanks for the thoughtful comment, Danny. Appreciate the chiming in. More bridge building between citizen scientists and the professional science community is always a good thing. Thanks for stopping by and the kind words. You and your perspective always welcome here.


    • Paul Cherubini says:

      “it’s not the day that they were born that changes them, its “The shorter days and cooler air” that triggers changes (which is relative to latitude).”

      Every year in far northern Minnesota, monarchs emerge in reproductive diapause beginning the first week in August when the days are still very long (15.5 hours) and BEFORE temperatures have started to decline and BEFORE the milkweed has started to turn yellow:

      So we still do not know for sure what environmental factors trigger diapause.

      • Dr. Danny says:

        The quote used was from monarchwatch.org and continued to say “The shorter days and cooler air of late summer trigger changes. In Minnesota this occurs around the end of August.” Below is a link to researchers that investigated diapause.


        Two factors that were shown to induce diapause were temperature and photoperiod. Although it wasn’t an exact photoperiod or temperature that caused it but instead decreasing day length and fluctuating temperatures (difference between day and night). Their criteria for diapause involved dissection of reproductive organs. The link provided from learner.org uses a criteria of gregarious nectaring for diapause. From a scientific point of view, this criteria is secondary, in that it doesn’t talk about reproduction. It is very possible that the feeding behavior did not correlate with the reproductive changes; they might not have been in reproductively in diapause.

      • Paul Cherubini says:

        Both gregarious nectaring (both sexes nectaring in close proximity to one another without displaying any sexual interest) and gregarious evening clustering (again involving both sexes) are proof of diapause. Here’s are Aug. 5, 2007 photos of clustering in that same area of extreme northwestern Minnesota: http://www.learner.org/cgi-bin/jnorth/jn-query-byday?1187632066. In other words, if the female butterflies in those photos were opened up it would be immediately apparent that they have undeveloped ovaries and no eggs and the males would have undersized reproductive organs as is typical of diapausers. Thus the Univ. of Minnesota researchers were mistaken to conclude “in Minnesota this [diapause] occurs around the end of August”. Also wrong to conclude “decreasing day length and fluctuating temperatures (difference between day and night)” are the environmental factors that trigger diapause. The factors remain unknown.

      • john barr says:

        OK Paul, lets pretend to be a scientist: What were the photoperiod and temperature fluctuations (day night temp fluctuations) experienced by the particular butterflies in your photographs?

        You have a single data point: Clustering Monarchs in 2007. From this behavior you infer a physiological state, diapause. This is a reasonable inference, yet it remains an inference, not a fact. As you state…..if …..they “were opened-up”. Had they been opened, you’d have a fact. All you have is an inference.

        What was the photoperiod experienced by the Monarchs you observed? Is it possible they migrated for half a day, how about a full day or even two full days before you observed them? Because you have only a single data point: Observed clustering Monarchs on August 5th, you are left to infer the photoperiod experienced. If they migrated south a day or two, the photoperiod would be different than the photoperiod in extreme northwestern Minnesota. It is an inference, not a fact. Again, a reasonable inference, possibly, but not a fact.

        What were the day night temperature fluctuations experienced by the monarchs you observed? Based upon the inference of hatching in close proximity to the clustering behavior, I guess one could explore weather reports and attempt to infer the temperature fluctuations experienced, but now you are building inference upon inference. We know nothing of the micro-climate these monarchs experienced.

        So let us review. A general statement was made about Monarchs in Minnesota. This statement was based upon an extrapolation of laboratory research. In the lab, photoperiod and temperature fluctuations have been shown to have an intricate dance. From your single data point and multiple inferences, you feel you have proved the lab results false. Not so fast my friend.

        In basic science statistics, degrees of freedom are equal to n-1. With your single data point, n, you are left with zero degrees of freedom.

        I am left with the question: Why are you so obsessed with “proving” the folks at Monarch Watch “wrong”? I have asked you this before in other forums, yet you continue to refuse to answer.

  4. I just found you blog and as a newbie to Monarchs, I appreciate the information. Even here in western NY we have had some warm weather days followed by really cold snowy ones. It is very different winter so far and I am not complaining as filling bird feeders in a blizzard isn’t that much fun. I hope that my continuing efforts to plants milkweed and other nectar plants gives monarchs and other butterflies a place to breed and to eat…Michelle

    • Monika Maeckle says:

      Michelle, thanks for stopping by. More milkweed is always a good thing. This weather is surely a wild card. Let us know how it goes.


  5. john barr says:

    Hi Monica,
    This is a very interesting article. I’ve got a couple of questions.

    Asclepias tuberosa? Sure looks like curassavica. (Bi-color flowers, alternate leaves, lack of hairs on the stems…….) Not to pick nits, but if doing science, then this level of ID would seem important. As I am sure you are aware, there is some controversy about planting non-native curassavica for several reasons among them the potential to foster a non-migrating gene pool. (Most native milkweed being dormant over the winter in Texas.)

    Also, I’m wondering about the word “brilliant” in your description of the Tacinid flies you observed. All the ones I’ve inadvertently hatched up in Austin have been plain brown-black in coloration. Are you referring to their coloration or the brilliance of their strategy?

    Thanks for all your efforts,
    John in Austin

    • Monika Maeckle says:

      HI John, and thanks for writing,

      You are not the first person to nail me on the milkweed. I believe you are right. Kip Kiphardt, our local Monarch monitoring expert, asked the same question, and I wondered myself.

      However when I first wrote about the milkweed patch the City official with whom I spoke told me these were all native plantings and the other plants in the area, red Texas sage, local passionflower vines, are native. So I assumed that the milkweed was also native. I am double checking on that and will make the correction. I’d be curious if the City THOUGHT they were planting natives when they were planting Tropical milkweed.

      As for the “brilliant” Tachinid fly, I was referring to the strategy. They are indeed very ordinary looking. I am constantly amazed at nature’s cleverness. The fly’s act is practically tantamount to a guerrilla birth.

      Thanks you again and stay tuned for an update. Just want to double check with my City contact next week.

      best wishes.


  6. Paul Cherubini says:

    John, last year Monarch Watch (Chip Taylor) said on dplex-l that no one knows for sure what environmental factors trigger diapause and I agree with him. Diapause reliably occurs the first week in August in northwest MN year after year, no exceptions. Example: in 2001 monarchs were observed clustering beginning Aug 1: http://www.learner.org/cgi-bin/jnorth/jn-query-byday?997730200. Plus Monarch Watch has had monarchs recovered in Mexico that were tagged in northwest MN and the upper Peninsula of Michigan the first week in Aug. Plus various scientists over the years have caught and dissected clustering monarchs in late summer and rarely ever found any that had eggs. So I think it would be cruel for me to kill and open up to additional clustering monarchs in northwest MN in early Aug for that purpose, but I guess I’ll need to do that this coming summer to convince the doubters that both clustering and gregariously nectaring female monarchs don’t have eggs. With regard to temperature fluctuations it is easy to check the various online sites that have archived weather data and you will quickly see there is no pattern of decreasing day or night temps between the first week in July and the first week in August in northwest MN nor an increase in the variability between day and night temps.

    • Dr. Danny says:

      “Noone knows for sure”. This means we dont know the system 100%. This does NOT mean we know 0%. I dont doubt that it is possible that some monarchs diapause outside of the proven conditions. But, just like the late season reproductives, this is the exception, not the rule. We need not create opposition in these forums, this is not their purpose. Citizens and Scientists already have enough distance between them. Research has shown that diapause can be induced by the factors mentioned, it wasnt just a correlation. Are there still more details to be unraveled? Absolutely. It may be that monarchs in the extreme NW MN use different cues than other geographic populations. Indeed that is one of the mysteries of the monarch, how they know when to leave, and how they know which direction, even when transported from one location to another. Dont focus on the conflict, focus on consolidation. Dont separate the citizen and scientist, focus on bringing them together. Creating doubt helps neither. Embracing curiosity is much more useful. This was the purpose of my original post.

      • Paul Cherubini says:

        “It may be that monarchs in the extreme NW MN use different cues than other geographic populations.” Dr. Danny, diapause appears to reliably occur the first week in August everywhere at latitudes of around 48 degrees North and higher. If university scientists ignore this reality then they will not be motivated to try and find out what cues induce this diapause in mid-summer when temperatures are high and stable.

        Same situation with many other monarch issues. Like the puzzle of how the butterflies “know” how to head Southwest in the late summer. In recent years citizens, not scientists, found out that fall migrants in Arizona can even fly northwest in the fall: http://swmonarchs.org/az-recoveries.php So this means the university scientists who are studying orientation will have to figure out what environmental imformation the butterflies perceive that causes to head northwesterly vs. southwesterly and southeasterly. Their previous explanation (that the butterflies have a time compensated sun compass that enables them to maintain a southwesterly flight bearing) is no longer a sufficient.

  7. Pingback: Butterfly FAQ: Pros and Cons of Tropical Milkweed and What to do with a Winter Monarch Butterfly Caterpillar or Chrysalis | texasbutterflyranch

  8. Pingback: Butterfly FAQ: Pros and Cons of Tropical Milkweed and What to do with a Winter Monarch Butterfly Caterpillar or Chrysalis | Hyatt Detroit

  9. Dr. Danny says:

    Exceptions, not the majority. See my post before. We have more to learn, no doubt.

    Thank you for changing the tone of your message. What cues induce diapause in mid-summer when temperatures are high and stable, for latitudes around 48 or more North (sorry i restricted my comment to include only those you mentioned)? We dont know these yet. It is curious and we should discover it, no doubt. Also, the monarchs that travel northwest in the fall is curious, someone should investigate. Indeed my example of grasshoppers eating dead honeybess, curious, hard to explain, someone should investigate. This is precisely the type of stuff that scientists and citizens who are not scientists can work together on. Let us celebrate that we can learn more!

    The entire idea behind citizen-scientist collaborations is that of being effective in understanding our world. There are not enough scientists to investigate everything. There are enough citizens to collect data though. We need citizens and their observations. To make it work, we must be truly collaborative and not competitive. Whether an explanation of a time compensated sun compass is 100% not sufficient, or that it is 90% sufficient and needs additional modification, is yet to be determined. Together, with minimal competition, we can be most effective in finding out. Let the investigations and observations go on!

  10. The milkweeds in the photo with Kelly Nall along the San Antonio River Walk are without question Asclepias curassavica (the Tropical American Milkweed).; they are NOT Asclepias tuberosa. The extensive breeding in the milkweed garden described in the above paragraphs support my contention that planting Asclepias curassavica in Texas (and all the Gulf Coast States) is almost certainly detrimental to monarchs by physiologically altering the butterflies’ reproductive behavior.

    Lincoln Brower.
    Sweet Briar College

    • john says:

      Linclon, I agree. I was just in Houston and observed Cats on Tropical in a museum garden. They looked particularly dark and lethargic. From my prior experience, I think they might be infected with tachinid flies. Active reproduction of tachinids in the winter in Texas would unnaturally increase the number of parasites awaiting the returning spring Monarchs. This would result in fewer next generation Monarchs.

  11. Pingback: Monarch Butterflies Make Milkweed Patch on San Antonio Museum Reach Home | The Rivard Report

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