Monarch Watch Monarch Watch

Monarch Population Status

22 April 2022 | Author: Chip Taylor

I have looked at a lot of monarch and weather data over the years in attempts to understand the factors that influence the development of the population. These factors include the number of monarchs returning to Texas from Mexico, whether the migration is early or late, the mean temperatures in March, the timing of the emergence of milkweeds, the abundance of nectar sources and the temporal and spatial distribution of egg laying by returning females. Additional weather-related factors include soil moisture and rainfall.

That’s a lot to track and it gets confusing when trying to sort through the data over decades since the impact of some factors is affected by others. For example, droughts have a greater impact when temperatures are high than when they are low. While it will take months to sort out how the population develops this year, I’ve put together some distribution maps of monarchs and milkweeds based on photos submitted to iNaturalist to see how the conditions this year compare to those in 2021. As you will see, the numbers this year do not compare well with last year. The numbers of returning monarchs were lower this past March and the numbers of photos of milkweeds were also lower. Monarchs seem to be well ahead of emerging milkweed.

Overall, the population doesn’t appear to be off to a good start. However, the numbers could be somewhat misleading. Last year, we had a special project with iNaturalist based on an attempt to determine how severely the massive freeze in Texas in February 2021 affected monarchs and nectar sources. It’s possible that our appeal for help last year generated an unusual number of submissions. Still, as I write (6 April), the first monarch has been reported in southern Kansas well ahead of the milkweeds.

Here are links to the reports generated through the collaboration with iNaturalist last year:

Monarchs and the freeze in Texas
https://monarchwatch.org/blog/2021/06/01/monarchs-and-the-freeze-in-texas/

Nectar plants used by monarchs during March in Texas
https://monarchwatch.org/blog/2021/05/25/nectar-plants-used-by-monarchs-during-march-in-texas/

Monarch – Danaus plexippus – 2022 N=392 (below left) and 2021 N=534 (below right)

Antelopehorn – Asclepias asperula – 2022 N=34 (below left) and 2021 N=207 (below right)

Green antelopehorn – Asclepias viridis – 2022 N=6 (below left) and 2021 N=45 (below right)

Zizotes – Asclepias oenotheroides – 2022 N=24 (below left) and 2021 N=68 (below right)

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Monarchs, milkweeds and O. e.: It’s time for a more holistic approach

19 April 2022 | Author: Chip Taylor

There have been many papers written on the relationship between monarchs and their neogregarine parasite Ophryocystis elektroscirrha, hereafter referred to as O.e. These papers have covered a number of topics including, infection rates, how spores are distributed by infected adults, how the relative attractiveness and overwintering persistence of tropical milkweed appears to contribute to the frequency of O.e., the relationship of sublethal infections on the fitness of monarchs, especially as it determines the ability to migrate, and frequency as it relates to continuous breeding and geographic distributions and others. These studies constitute a useful baseline or foundation for further studies. In this short article, I’m going to argue that to fully understand the relationship between monarchs and O.e. we need a more comprehensive approach, one that accounts for the seasonal and geographic dynamics of the monarch population, the density and frequency dependent interactions in the system, the impacts of other predators and parasites and the effects of weather on the outcomes. While I’m advocating a holistic approach, I’m not attacking the research conducted to date nor am I claiming to have the answers. However, I do feel that a broader understanding of the complexities of the interactions in monarchs’ annual cycle and its interactions with all components in the system will be helpful. There are some obvious relationships that are begging for data.

O.e. has a unique life-history that involves ingestion of spores by larvae but ends with masses of spores on the outside of the adult host. Here is the short version of that process. To become infected, a monarch larva consumes the chorion (egg shell) along with O.e. spores shed on the egg or the surrounding leaf surface during oviposition. A larva can also eat spores deposited on milkweed leaves by infected or contaminated monarchs that have landed on the leaves. The spores consumed by the caterpillar “germinate” in its alkaline gut and a malaria-like stage of O.e. (sporozoite) migrates through the gut wall to the tissues (hypoderm) beneath the caterpillar’s skin. This stage is followed by vegetative reproduction and then a period of quiescence. Late in the pupal stage, variously said to be the 8th day of pupation or three days before emergence, O.e. goes through a process of reproduction that results in a massive production of spores (sporulation) just beneath the cuticle of the pupa and on the outside of the developing monarch. Upon emergence, the adult monarch can carry extremely large numbers of spores, especially on the abdomen. The dust-like spores are lost progressively through the life of an infected adult monarch. O.e frequency is usually determined from sticky taped samples of scales taken from a monarch’s abdomen. Upon inspection with a microscope, high numbers (thousands) of spores indicate infection, low numbers (a hundred or less) indicate contamination through contact with other monarchs or contaminated surfaces. In the wild, an unknown portion of O.e. infected larvae, pupae and adults with crumpled wings die before they are able to take flight to reproduce or migrate, and therefore are not included in the sampling to determine the frequency of O.e. Thus, it’s likely that the mortality and morbidity due to O.e. is greater than measured. This mortality can be seen in badly infected monarch cultures, but we have no idea how common it is in the wild.

I’m going to start with migratory culling and how that relates to the carryover of O.e. spores from one year to the next. While it’s clear that a significant proportion of the infected monarchs are eliminated during the migration due to reduced life span and flight capability, there is no data indicating that infected monarchs return in the spring to establish the O.e. infection rate. If we assume that the culling eliminates nearly all of the highly infected individuals either during the migration, through the winter or during the migration from the overwintering sites to Texas, that means that O.e predominantly starts the next year as incidental spores carried on non-infected individuals (also referred to as contaminated or spore infested) through horizontal transfer due to contact with other individuals or contaminated surfaces. The proportion of returning monarchs that are contaminated with O.e. spores as they reach Texas is unknown. That proportion and how it varies from year to year is critical to our understanding of how O.e. increases each year. On the other hand, if a substantial number of infected females survive the migrations and reach Texas in the spring, the distribution of spores on the eggs they lay, and the milkweeds they contact, would result in a more efficient way to establish O.e.

The next consideration is how those spores are distributed on milkweeds as these returning monarchs move northward. The returning monarchs carrying spores advance at a rate of 30-55miles per day with some mating and with females laying eggs as they move northward. As this population progresses, the spores are dispersed on the milkweed foliage through egg laying and other foliage due to nectaring and resting. In effect, there is a trail of spores which thins out with increasing latitude to the point at the northern limit reached by overwintered monarchs where there are almost no spores to be ingested by monarch larvae. In other words, the loss of spores fits a decay function, i.e., a frequency of spores that declines with distance. In this scenario, relatively few of the first-generation monarch larvae will ingest spores and most of those larvae that do so will originate from the most southern range with milkweeds. However, we need to consider “egg dumping”. This term refers to the tendency of female monarchs, either the same female, or multiple females, to lay multiple eggs on relatively scarce new milkweed shoots. This concentration of egg laying and multiple touches by contaminated females is likely to have the effect of increasing the numbers of infected first-generation adults. Since egg dumping is usually reported only when milkweed shoots, or even mature plants, are scarce, this dynamic illustrates one of the frequency/density relationships in the system. If the abundance of O.e. contaminated females is high relative to the number of available shoots or mature plants, that favors multiple touches and multiple deposits of spores (frequency) along with eggs on relatively small numbers (density) of plants. That will certainly lead to an increase in O.e. What we don’t know is how much egg dumping occurs, how it differs regionally and from year to year. It seems likely that since we know that milkweeds are less abundant in some regions, such as the SE, that egg dumping is more common in that region. On the other hand, there is variation in the phenology of both milkweed growth and monarch occurrence such that, in some years, if milkweeds have emerged in abundance before the arrival of monarchs, the dumping will be less common resulting in lower rates of infection than in years when shoots are scarce. These dynamics could result in significantly different proportions of infected first-generation monarchs moving north from different regions as well as in different years. As monarchs continue to move north in May and early June, egg dumping is less of a factor since milkweeds have typically emerged and are abundant N of 40N at this time.

First generation monarchs begin moving N in the last week of April and they too, as a population, will leave a trail of spores which will also decline due to distance. It follows that relatively few of the monarchs reaching the latitudes N of 40N, but especially above 45N, will carry spores to the most northern and eastern latitudes and longitudes. Given what is known of migratory culling, it is likely that most of the spore-carrying first generation monarchs moving north will be either lightly infected or simply contaminated with spores through horizontal transfer.

How the O.e. numbers build up after the recolonization has occurred will depend on a number of factors starting with the number of recolonizing monarchs and the proportion carrying spore loads. Beyond that, we have to be concerned about the abundance and spatial distribution of milkweeds. These considerations take us back to the density and frequency-dependent relationships that determine the infection rate for the next generation. If there are low numbers of infected and contaminated individuals and milkweeds are exceedingly abundant relative to the monarch numbers, the infection rate for the next generation might increase slightly but will still be low. On the other hand, if the numbers of infected and contaminated females are high relative to the abundance of milkweeds, the frequency of O. e. will increase significantly. In highly fragmented environments where the distances between patches are substantial, there will be hot spots where the incidence of O.e. will be quite high if infected and contaminated females continue to return to the same plants for oviposition. Since there are few regions with an even distribution of milkweeds, it is likely that a fine-grained approach to sampling will find that Oe varies within regions as a function of monarch abundance as well as the spatial distribution and abundance of milkweeds.

The escape hypothesis, which posits that monarchs disperse to escape high frequency infection rates by O.e., doesn’t really fit with the monarchs’ seasonal migrations. In the spring, monarchs returning from Mexico simply migrate – distributing eggs (progeny) as the migration advances. They are not escaping a high incidence of O.e. That can also be said of the first- generation monarchs that migrate north from late April to early June. These monarchs are advancing into areas where milkweed is more abundant and where temperature and moisture conditions are more favorable for reproduction. If anything, monarchs are abandoning the southern latitudes due to the tendency for two of the more common milkweeds to senesce during the summer months and for high temperatures to be less favorable for reproduction. Further, once the migration stops at each latitude in June, monarchs disperse locally in search of milkweeds. Thereafter, the buildup of O. e. is a function of the size of the next generation, number of generations, abundance and distribution of milkweeds, interactions with predators and parasites that eliminate infected larvae and the weather. In effect, once the migration has stopped, the monarchs are stuck in one place irrespective of the buildup of O.e. or predators and parasites. One could argue that, if selection had favored escape from O.e., that the first-generation monarchs would not stop migrating across the latitudes through May and early June (See the puzzle solution –). The escape hypothesis seems to suggest that monarchs are aware of the O.e. infection rate or the buildup of predators and parasites. Cognition in insects? No, I don’t think so. It seems far more likely that dispersal and migration by monarchs is a selective response to changes in habitat quality.

In terms of the seasonal breeding dynamic, there is very little continuous reproduction south of 35N from late May until August. That’s related to the fact that, in much of the south, milkweeds senesce during the summer, and it is simply too hot for sustained reproduction. From that perspective, monarchs have been selected to vacate degrading habitats. That said, there are some exceptions where reproduction is continuous in coastal cities with lots of planted milkweed such as Houston and New Orleans. Based on that observation, and on the behavior of monarchs in areas such as southern Florida where reproduction is continuous, it seems that monarchs respond to the availability of resources rather than O.e., as well as other parasites and predators that are also common in those areas. O.e. infection rates are known to be high in these areas yet there appears to be no “escape”.

There is also the mid-summer migration in which monarchs move south of 40N to recolonize the southern latitudes from late July through the first three weeks of August. Some are probably carrying spores S from the northern latitudes. These monarchs are not “escaping” from areas with high frequencies of O.e. any more than the first gen monarchs are as they move N.

Because we can test for it, and determine its frequency, O. e. inspires concerns about the degree to which this parasite depresses the monarch population. Similar concerns have been voiced about the impact of introduced fire and crazy ants, ladybird beetles, European paper wasps and tachinid flies on monarch numbers. And then there are the periodic increases of resident parasites and predators that also take a toll. All of these species surely have an impact on monarch numbers, but to put these losses into context, we have to know where and when in the season these impacts occur. And in the case of monarchs that migrate, we have to know whether monarchs from all reaches of the eastern population have equal or strongly different probabilities of overwintering in Mexico and contributing to the population the following spring.

Lastly, O.e. appears to be a “self-limiting” disease/infection/organism. That is, a species that is capable of reducing the population of a host to a relatively low level from which, in time, the population will recover. In other words, monarchs and O.e. will cycle because of the spatial and temporal complexity of the environment. That complexity is related to the seasonal and spatial distribution of milkweeds and the presence of other species and weather conditions. There are a large number of parasites and predators that prey on monarch eggs, larvae and pupae such that the percentages reaching the adult stage are estimated to be 1-3%. As these species prey on monarchs, they also eliminate O.e. infected immatures. In some cases, the mortality rate due to these species approaches 100%. By eliminating adult monarchs and therefore reducing the distribution of spores to milkweed leaves and giving time for the O.e. spores that are present to degrade, portions of the larger range become monarch and O.e. free, allowing recovery when these locations are found by females that don’t carry spores. These actions create the complexity and escape in space monarchs need to recover from high levels of infection that reduce the population in other locations. Again, in these cases, the “escape” is simply an artifact of the constant dispersal conducted by monarch females in search of host plants. Fundamentally, there is nothing unique here since this dynamic is common to a large number of interactions between hosts and the species that prey on them. These dynamics are similar to those illustrated by a series of predator/prey and parasite/prey experiments conducted in greenhouses decades ago. In those experiments, predators or parasites could eliminate a host and themselves in the simplest of habitats. Complexity often produced cycles of hosts and parasites since the diversity/complexity of the habitats afforded escape by the hosts in time and space. Most greenhouse managers are well aware of the complexities involved in trying to control greenhouse pests with predators or parasites. Success is often temporary due to the ability of the prey (pest) species to escape in time and space.

Many of the hypothetical deductive scenarios I have outlined can be tested experimentally or, in some cases, through sampling that follows rigid protocols.

Conclusions

To understand the relationship between O.e., monarchs, milkweeds, predators, parasites and weather, we have to lay a foundation for the annual cycle of both monarchs and O.e as well as the seasonal, local and regional dynamics of the other species that interact with monarchs in a manner that modifies the O.e. frequency. In addition, we need to understand the density and frequency dependent interactions between monarchs, milkweeds and O.e. At present, our understanding of passive/horizontal transfer of O.e. spores is limited, and knowledge of the conditions, such as UV and high temperatures, that result in the degradation of O.e. spores is lacking. These conditions could explain the relatively low incidence of O. e. in Arizona in spite of the relatively low and highly fragmented distribution of milkweeds in much of that state.

Looking forward, in coming years, the continuing loss of grasslands, along with land conversion associated with development, will result in a loss of milkweeds, an increase in fragmentation and an increase in O.e. It should be noted that the recent increase in O. e. followed the adoption of herbicide tolerant crop lines in the early 2000s and the later adoption of the renewable fuel standard in late 2007 both of which resulted massive losses of milkweeds. These losses and the resulting increase in fragmentation could well account for the increase in O.e since the early 2000s. References to habitat losses due to these factors can be found in previous posts to this Blog.

Recent publications

Majewska, A. A., Davis,A. K., Altizer, S. and Jacobus C. de Roode. 2022. Parasite dynamics in North American monarchs predicted by host density and seasonal migratory culling. Journal of Animal Ecology.

Dargent, F., Gilmour, S. M., Brown, E. M., Kassen, R., and Heather M. Kharouba. 2021. Low prevalence of the parasite Ophryocystis elektroscirrha at the range edge of the eastern North American monarch (Danaus plexippus) butterfly population. Can. J. Zool. 99: 409–413.

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Monarch Watch Update February 2022

9 February 2022 | Author: Jim Lovett

This newsletter was recently sent via email to those who subscribe to our email updates. If you would like to receive periodic email updates from Monarch Watch, please take a moment to complete and submit the short Google Form at monarchwatch.org/subscribe/

Greetings Monarch Watchers!

This is a relatively brief update, primarily serving as a follow-up to some items in last month’s email. Thank you for your continued interest and support!

Included in this issue:
1. Monarch Watch One Day Fundraising Event
2. Monarch Watch Tag Recoveries
3. Free Milkweed Programs
4. A Return to the Monarch Puzzle
5. About This Monarch Watch List

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1. Monarch Watch One Day Fundraising Event
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As promised last month, below is the official announcement of this year’s one day fundraising event taking place next week. We will send out a reminder on the day of the event to give you easy access to the link, should you like to participate. Help us continue our mission to restore habitats for monarchs and native pollinators – donations of any amount do help and are greatly appreciated.

On Thursday, February 17th Monarch Watch will again be featured in the University of Kansas’ annual “One Day. One KU.” 24-hour fundraising campaign. This event provides an opportunity for Monarch Watchers all over the globe to come together and show their support of our programs.

This year you will be able to take advantage of FOUR matching opportunities to increase the impact of your gift:

1. Monarch Watch Director Chip Taylor and his wife, Toni, are matching dollar-for-dollar all gifts up to $4,000.

2. Dedicated supporter, Janet Lanza, will match dollar-for-dollar all gifts to Monarch Watch, up to $5,000!

3. KU alumna and Monarch Watch supporter, Susan Lordi Marker, will match dollar-for-dollar all gifts, up to $5,000!

4. An anonymous donor will match dollar-for-dollar all gifts up to $5,000 to Monarch Watch and encourages others to donate.

Additionally, many employers will match employee gifts to Monarch Watch so that is yet another opportunity!

To make a donation online the day of the event, visit https://kansas.scalefunder.com/amb/monarch

To make a gift by phone anytime between now and the day of the event, call KU Endowment at (888) 653-6111 – just be sure to mention that you would like to give in support of Monarch Watch for the one-day event.

Don’t forget to check your email on February 17th for the reminder and link – thank you!

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2. Monarch Watch Tag Recoveries
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Many of you have been asking about when tag recoveries for the 2021 tagging season will be posted online.

Recoveries from the overwintering sites in central Mexico are typically reported to us in February/March and posted online in March/April once everything is received and verified. We will make an announcement via our email updates so stay tuned!

The tag recoveries within the U.S., Canada and northern Mexico are typically posted in January/February once everything has been vetted – a link to the list is now posted online at https://monarchwatch.org/tagrecoveries

As a reminder, if you have not submitted your tagging data to us yet, it is not too late! Complete information (including links to the tag data submission form and recovery lists) is available on our Monarch Tagging Program page at https://monarchwatch.org/tagging

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3. Free Milkweed Programs
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For habitat restoration projects

New this year, we will be able to distribute free milkweeds to many areas of California (in addition to areas east of the Rocky Mountains) – please see the link below for complete details. To qualify, applicants must have a minimum of two acres (one acre in CA) to restore to natural, native habitat, and have a management plan in place. Milkweeds are awarded on a first come, first served basis, so apply early.

Those awarded free milkweeds need only pay shipping/handling, which is modest compared to the value of the plants. Please help us spread the word by sharing widely. For more information and to apply, please visit:

https://monarchwatch.org/free-milkweed-restoration

For Schools and Nonprofits

The Free Milkweeds for Schools and Nonprofits Grant is in its 8th year and we are still distributing free milkweeds to those who qualify. Through the generous support of the Natural Resources Defense Council, this program provides funding for 6000 plants. Each recipient receives one full flat of milkweed plants to be added to a public garden. Schools, libraries, nature centers and museums are examples of past recipients. This program is available to applicants in California and all states east of the Rocky Mountains. The application can be found here:

https://monarchwatch.org/free-milkweed-schools-nonprofits

Sorry, this program is not intended for private yards or free milkweed giveaways.

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4. A Monarch Puzzle – Chip Taylor
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The contest is still on.

“When does the migration northward end – or does it”?

In a monthly update posted in June of 2003 with the above title, I wrote “My guess is that the migration stops at each degree of latitude northward at a particular date, that these dates can be predicted, and that all directional migration stops before the 21st of June at all latitudes.” Over the years I have returned to that question several times and have asked myself repeatedly what might the monarchs be responding to that would stop directional flight. The question is basically – what is changing and how is that change perceived by the monarchs? Further, whatever the cue is, it has to be similar over all latitudes.

So, what could it be? I think I’ve figured it out, and I think you can too. That was the basis for the puzzle in the last email update (see original text below). The challenge was to identify a factor common to all locations that could explain why monarchs would stop directional flight on a certain date.

Fourteen people submitted answers to the puzzle by the end of January. None of them arrived at the answer I was seeking and that’s not surprising. It’s a difficult question, and it took me a long time to arrive at the pattern that I think explains when monarchs stop directional flight in late May to early June from Dallas to Winnipeg.

All of the respondents mentioned seasonal changes, and these ranged from temperatures and winds to changes in vegetation, daylength and sun angle. However, none of them pointed to a specific change that was common to all four sites – specifically a change that the monarchs might respond to.

I’m confident that many of you can get to the answer I did, and to get you there, I’m are going review a few things and direct you to a website. (In the original puzzle, the dates for St. Paul and Winnipeg were incorrect, being 9 and 12 respectively. They are corrected in the table below).

Table 1. Seasonal metrics for specific locations.

Location	Date	Daylength	Sun angle (SASN)	Solstice	22nd
Lawrence, KS	5 June	14h48m12s	73.63°	74.47°	74.46°
Ames, IA	7 June	15h9m33s	70.78°	71.42°	71.41°
St. Paul, MN	8 June	15h31m41s	67.95°	68.50°	68.49°
Winnipeg, CAN	11 June	16h18m0s	63.23°	63.55°	63.54°

It’s clear from this table that daylength, sun angle at solar noon and at the solstice (21 June) all change with date and latitude. So, none of these changes per se can explain why monarchs might stop migrating on the dates suggested. Yet, there is change. So, the question becomes is there a feature of the changes that are occurring that is common to all locations? There are a number of sources on the internet that are useful in this context. My favorite is SunCalc ( https://suncalc.org )

For a short tutorial on how to use SunCalc please visit https://monarchwatch.org/blog/2021/08/17/some-notes-on-the-sun-angle-at-solar-noon-sasn-and-the-passage-of-the-migration/

Table 1 was assembled using SunCalc, but there is more that can be learned using this site. To get to where I did, think about what the monarchs may or may not be responding to as the season changes. You can get to the answer using suncalc.org, and if you get there, you may react the way I did. It was kind of a eureka moment – except I didn’t say eureka!

If you think you have figured out what these four locations have in common on the dates indicated and have an explanation for why migratory flight probably stops on these dates, send your answer to Monarch Watch at monarch@ku.edu (with “Puzzle Submission” in the Subject line) by the 28th of February 2022. We will reward the three best answers with a copy of the new migration board game “Mariposas”.

A Monarch Puzzle – original text

Get out your pencils!

We know that directional flight (migration) by first generation monarchs that have moved northward stops sometime in June, but we aren’t sure when it stops, where it stops or why. I have an idea based on one data point that may explain the when and why for a series of latitudes. I’m going to explain the observation and tell you when I expect directional flight ends at the latitudes of Ames, IA, St Paul, MN and Winnipeg, Manitoba.

Many years ago, I asked an undergraduate to pay special attention to directional flight by monarchs in late May and June. We knew that first generation monarchs from the South Region (Texas and Oklahoma) were moving through the area at that time on the way north to the summer breeding grounds north of 40N. We also knew that that migration stopped suddenly but we didn’t know when or why. She went to a location with lots of common milkweed patches at which the passing monarchs would stop briefly but then continue flying N/NE. The last day she spotted monarchs moving to the N/NE was the 5th of June. That got me thinking, if I know when they stopped in Lawrence, could I extrapolate from the conditions on the 5th of June to those in other latitudes? Well, I’ve done so, and the prediction is that directional flight should stop in Ames on the 7th, in St Paul on the 9th and Winnipeg on the 12th.

So here is the puzzle: what do the dates at the latitudes represented by these cities have in common with the conditions that occur on the 5th of June in Lawrence, Kansas?

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5. About This Monarch Watch List
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Monarch Watch ( https://monarchwatch.org ) is a nonprofit education, conservation, and research program affiliated with the Kansas Biological Survey & Center for Ecological Research at the University of Kansas. The program strives to provide the public with information about the biology of monarch butterflies, their spectacular migration, and how to use monarchs to further science education in primary and secondary schools. Monarch Watch engages in research on monarch migration biology and monarch population dynamics to better understand how to conserve the monarch migration and also promotes the protection of monarch habitats throughout North America.

We rely on private contributions to support the program and we need your help! Please consider making a tax-deductible donation. Complete details are available at https://monarchwatch.org/donate or you can simply call 785-832-7374 (KU Endowment Association) for more information about giving to Monarch Watch.

If you have any questions about this email or any of our programs, please feel free to contact us anytime.

Thank you for your continued interest and support!

Jim Lovett
Monarch Watch
https://monarchwatch.org

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Monarch Watch Update January 2022

6 January 2022 | Author: Jim Lovett

Greetings Monarch Watchers and Happy New Year to all!

As many of you already know, Monarch Watch will be celebrating 30 years of education, conservation, and research in 2022 – WOW! We are not yet sure how we will mark this milestone, but there will certainly be a retrospective component and maybe an event or two. We will keep you informed via our blog, email updates, and social media. Thank you for your continued interest and support!

Included in this issue:
1. How Many Hectares in 2021-2022?
2. Western Monarchs
3. Monarch Watch One Day Fundraising Event
4. Monarch Watch Tagging Kits for 2022
5. Submitting Tag Data
6. Monarch Watch Mobile App
7. Free Milkweed Programs
8. A Monarch Puzzle
9. About This Monarch Watch List

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1. How Many Hectares in 2021-2022? – Chip Taylor
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Each year, at about this time, I administer a test – to myself. I have one question. How big, in term of hectares*, will the overwintering population be this year?

Technically, I fail the test every time and expect to. Realistically, it would be virtually impossible to correctly predict the overwintering numbers given the number of variables involved in each migration.

I look at many factors and draw on the historical record to arrive at a prediction. The conditions during the spring in Texas, the recolonization of the northern breeding areas in May, the summer temperatures, the weather during the migration and the availability of nectar sources in Texas all differ from year to year and all factor into the number of monarchs that reach the overwintering sites. The challenge for me is to assess each of these conditions for a given year and to compare these outcomes with the record that goes back to 1994.

After considering all of these factors for this past season, I came up with the following estimate: 0.8-1.2 hectares. Ouch! That’s low and lower than the 2.01 hectares measured last year. In fact, if 1.2 hectares this year, that would be the lowest number since the winter of 2014-2015. I know that that is not what anyone wants to hear, and I don’t want to accept those numbers myself, but that is what my assessment tells me. My history with these estimates is fair, but I usually underestimate the size of the population which means that I’m overestimating the negative impact of one or more factors. These over and under estimates speak to my goal which is to develop a deep understanding of all the factors that determine the size of the population. Being wrong goes along with learning how to refine my estimates. Last year my estimate for the hectare total was almost spot on – 2.0 hectares vs a measured 2.01 hectares. It was more of a guess than a data-based prediction, but I’ll take credit for being close. There are reasons to think I will be close again this year and other reasons to predict that the number will be higher.

For a detailed discussion of this season’s prediction please see the expanded “How many hectares in 2021-2022?” article posted today via the Monarch Watch blog.

*One hectare is equal to 2.47 acres. One acre is approximately the area of a football field exclusive of the end zones.

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2. Western Monarchs – Chip Taylor
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My father was a Certified Public Accountant, and had I demonstrated a facility for numbers, I might have become a CPA as well. Instead, I became a biologist which I naively assumed would mean that I wouldn’t have to work with numbers – at least not a lot. As it turns out, understanding monarchs, or more accurately, attempting to understand monarchs, requires a lot of number crunching. But that only works if we have some numbers to work with, and if the numbers are reasonably accurate.

This brings me to a monarch puzzle. Namely, how did the Western monarch population grow from an overwintering number of 1,914 in 2020 to over 200,000 in 2021? Both numbers are based on Xerces-sponsored Thanksgiving Day Counts. Each count involves an examination and estimation of the number of monarchs at 261 known overwintering locations and the search for new sites which are often on private land. At many sites, the number of monarchs is so low, the count is an actual count rather than an estimate. That was mostly the case last year and the Thanksgiving number was followed by an end of the year accounting that produced only 1,049 monarchs. The decline from 1,914 to 1,049 was not unexpected. From the end of a breeding season in September and October (depending on location), the population declines until the end of the first reproductive period in April.

There seem to be three possibilities, 1) monarchs originating from Mexico recolonized the breeding areas in the West in March and April, 2) there were thousands of overwintering monarchs that clustered at sites that have never been discovered or 3) that some monarchs that breed along the coast during the winter months responded to seasonal cues in March and moved inland where they gave rise to a first generation of monarchs that colonized the summer breeding ranges in the West, particularly those areas to the east and north of California.

I’ve attempted to determine if there is support for any of these possibilities and those interested in a deep dive into the numbers should read the expanded “Western Monarchs” article posted today via the Monarch Watch blog.

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3. Monarch Watch One Day Fundraising Event
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Monarch Watch will again be featured in the University of Kansas’ annual “One Day. One KU.” 24-hour fundraising campaign which will take place in mid-February. The event will provide an opportunity for Monarch Watchers all over the globe to come together and show their support of our program.

Last year many of you commented that you would’ve liked more notice of this event so this is just a quick heads up before an official announcement that will be made in the coming weeks. Stay tuned!

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4. Monarch Watch Tagging Kits for 2022
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Monarch tagging continues to be an important tool to help us understand the monarch migration and annual cycle. We are now accepting PREORDERS for the 2022 fall tagging season and kits will be sent out in the fall, ahead of the migration in your area. If you would like to tag monarchs this year, please order your tags as early as possible!

Monarch Watch Tagging Kits are only shipped to areas east of the Rocky Mountains. Each tagging kit includes a set of specially manufactured monarch butterfly tags (you specify quantity), a data sheet, tagging instructions, and additional monarch / migration information. Tagging Kits for the 2022 season start at only $15 and include your choice of 25, 50, 100, 200, or 500 tags.

Monarch Watch Tagging Kits and other materials (don’t forget a net!) are available via the Monarch Watch Shop online at https://shop.monarchwatch.org – where each purchase helps support Monarch Watch.

Complete information including datasheets and instructions are available on the Monarch Tagging Program page at https://monarchwatch.org/tagging

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5. Submitting Tag Data
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Thousands of you have submitted your recent tag data to us by mail or via our online submission form – thank you! We are still receiving data sheets and if you haven’t submitted your data yet (for 2021 or even previous years) it is not too late. Please review the “Submitting Your Tagging Data” information on the tagging program page then send us your data via the Tagging Data Submission Form.

Complete information is available at https://monarchwatch.org/tagging if you have questions about submitting your data to us and we have conveniently placed a large “Submit Your Tagging Data” button on our homepage at https://monarchwatch.org that will take you directly to the online form.

There you can upload your data sheets as an Excel or other spreadsheet file (PREFERRED; download a template file from https://monarchwatch.org/tagging ) or a PDF/image file (scan or photo).

If you have any questions about getting your data to us, please feel free to drop Jim a line anytime via JLOVETT@KU.EDU

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6. Monarch Watch Mobile App
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A newly developed Monarch Watch mobile app (for iOS and Android) will make it easier for many taggers to record butterflies as they are tagged and submit data electronically. The beta testing of the app in the last few months has gone well, and we hope to launch it for general use during the 2022 tagging season. We will have much more to say about this in the coming months.

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7. Free Milkweed Programs
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For habitat restoration projects

New for Spring 2022 — Free Milkweeds for California restoration!

Monarch Watch will once again be distributing free milkweeds for planting in large-scale habitat restoration projects for Spring 2022. Since this program began in 2015, almost 252,000 milkweeds [edit: more than 650,000 milkweeds] have been planted in restored habitat throughout much of the range of the eastern monarch population. New this year: Help the Western monarch population with FREE MILKWEEDS FOR MOST AREAS OF CALIFORNIA! To qualify, applicants must have a minimum of two acres (one acre in CA) to restore to natural, native habitat, and have a management plan in place. Milkweeds are awarded on a first come, first served basis, so apply early.

https://monarchwatch.org/free-milkweed-restoration

For Schools and Nonprofits

https://monarchwatch.org/free-milkweed-schools-nonprofits

Sorry, this program is not intended for private yards or free milkweed giveaways.

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8. A Monarch Puzzle – Chip Taylor
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Get out your pencils!

So here is the puzzle: what do the dates at the latitudes represented by these cities have in common with the conditions that occur on the 5th of June in Lawrence, Kansas?

If you think you have figured out what these four locations have in common on the dates indicated and have an explanation for why migratory flight probably stops on these dates, send your answer to Monarch Watch at monarch@ku.edu (with “Puzzle Submission” in the Subject line) by the 31st of January 2022. We will reward the three best answers with a copy of the new migration board game “Mariposas”.

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9. About This Monarch Watch List
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Monarch Watch ( https://monarchwatch.org ) is a nonprofit education, conservation, and research program affiliated with the Kansas Biological Survey & Center for Ecological Research at the University of Kansas. The program strives to provide the public with information about the biology of monarch butterflies, their spectacular migration, and how to use monarchs to further science education in primary and secondary schools. Monarch Watch engages in research on monarch migration biology and monarch population dynamics to better understand how to conserve the monarch migration and also promotes the protection of monarch habitats throughout North America.

If you have any questions about this email or any of our programs, please feel free to contact us anytime.

Thank you for your continued interest and support!

Jim Lovett
Monarch Watch
https://monarchwatch.org

If you would like to receive periodic email updates from Monarch Watch, you may SUBSCRIBE via https://monarchwatch.org/subscribe

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Western Monarchs

6 January 2022 | Author: Chip Taylor

My father was a Certified Public Accountant, and had I demonstrated a facility for numbers, I might have become a CPA as well. Instead, I became a biologist which I naively assumed would mean that I wouldn’t have to work with numbers – at least not a lot. As it turns out, understanding monarchs, or more accurately, attempting to understand monarchs, requires a lot of number crunching. But that only works if we have some numbers to work with, and if the numbers are reasonably accurate, which brings me to a monarch puzzle. Namely, how did the Western monarch population grow from an overwintering number of 1,914 in 2020 to over 200,000 in 2021? Both numbers are based on Xerces sponsored Thanksgiving Day Counts. Each count involves an examination and estimation of the number of monarchs at 261 known overwintering locations and the search for new sites which are often on private land. At many sites, the number of monarchs is so low, the count is an actual count rather than an estimate. That was mostly the case last year and the Thanksgiving number was followed by an end of the year accounting that produced only 1049 monarchs. The decline from 1914 to 1049 was not unexpected. From the end of a breeding season in September and October (depending on location), the population declines until the end of the first reproductive period in April.

So, from a January number of 1049, how many females would we expect to be alive in March at the beginning normal reproduction in California? We can expect attrition to continue from January to March, but let’s assume that 70% survive. That’s probably high, but let’s go with it. That leaves 734 individuals. Since the sex ratio shifts in Mexico from being dominated by males at the beginning of the winter season to being female dominated at the end of the season, let’s assume that applies to these numbers. At best, that would mean that 55-65% of the survivors would be females. Let’s say it’s 60%, or 441 females. The next question is – Is it possible for 441 females to produce a population of 200,000 monarchs in 3-4 generations? I don’t think so. I’ve done the math several times, and you can as well*. So, if we can’t see a way to account for a fall population of 200,000 from the overwintering numbers, it means we are missing something, and the next question is what could that be? There seem to be three possibilities, 1) monarchs originating from Mexico recolonized the breeding areas in the West in March and April, 2) there were thousands of overwintering monarchs that clustered at sites that have never been discovered or 3) that some monarchs that breed along the coast during the winter months responded to seasonal cues in March and moved inland where they gave rise to a first generation of monarchs that colonized the summer breeding ranges in the West, particularly those areas to the east and north of California.

To determine if there is any support for the idea that the West was recolonized by monarchs from Mexico, I examined the first sightings records posted to Journey North and all the images of monarchs posted to iNaturalist for March and April. There is nothing on either site that supports the hypothesis that monarchs returned from Mexico in good numbers this past spring. If they did, this influx was missed by all those who are inclined to report monarch sightings.

The possibility that there are coastal or even inland overwintering sites in California that have never been discovered is real. New sites are discovered from time to time. Given the length of the coastal area, and the possibility that some areas are relatively inaccessible, there is the possibility that thousands of monarchs overwintered at locations that weren’t part of the surveys in 2020. There are reasons to think that the conditions for establishing overwintering clusters were different in 2020. The mean temperatures in California for both September and October 2020 were the highest in the record. October was +6.7F above the long-term average. It is during these months that monarchs migrate toward the coast with numbers beginning to show up at the overwintering sites in mid-October. Monarchs don’t migrate when the temperatures are in the 90s and often not when in the mid 80s. Rather, they seek cooler sites. This behavior might have led them to cluster in atypical locations. Under these conditions, monarchs that are unable to avoid extreme high temperatures often become reproductive and drop out of the migration. Both of these things could have happened in September-October 2020. Although it’s possible, even likely, that there are alternative overwintering sites in California, there is simply no evidence that such sites played a role in the number of monarchs that survived the winter in 2020-2021.

The third explanation, that offspring of winter breeding monarchs moved inland to reproduce in March and April is a possibility but, again, there is no precedent for such an occurrence. However, given the widespread reproduction this past winter reported to the Monarch Larval Monitoring Project (view summary of California data by year), this possibility shouldn’t be discounted. The fact is, we know little about the population dynamics of monarchs that reproduce during the winter months in California. So, what is the possibility that some recently emerged offspring of coastal breeding monarchs do move inland in March to reproduce? To answer that question, we need to know how monarchs respond to seasonal cues that might initiate migratory behavior. To dive into that topic, let’s look at the daylength/celestial conditions that occur during the migration northward in Mexico to see if they apply to California. We know that mating increases at the overwintering sites in Mexico in mid-February after the sun angle at solar noon (SASN) increases to 57 degrees. The date of the migration northward from the colonies is temperature dependent but usually starts around the 1st of March. The SASN at that time is 63 degrees. The possibility that the northward migration from Mexico is associated changes in the SASN is supported by the graphic (Fig 1) David Gibo and I put together based on first sightings assembled by Elizabeth Howard and her team at Journey North years ago**. The 63 SASN for a beginning of the departure from Mexico doesn’t seem to match a tracking of 56 SASN once the monarchs reach Texas. However, it is possible that the cues to leave actually began weeks earlier when the SASN reached 56 or 57 degrees. Preparing for departure from the colonies may in fact take several weeks since it is still cool at the Mexican sites, especially at night, which could delay the physiological and behavioral responses to the changing conditions. Once monarchs leave the overwintering colonies, they encounter consistently higher temperatures and move northward about 50-55 miles a day, which is faster than the pace of the SASN in degrees. The SASN advances about one degree, or 69 miles, every three days***. The difference in the respective paces allows the butterflies to soon track an SASN of 56 degrees – if the weather allows.

As to prepping to leave the coastal areas for the interior, cool conditions along the coast and the nearby foothills could result in a delay in physiological and behavioral development and could determine when monarchs move inland. It may help, when thinking of these dynamics, to remember that overwintering monarchs have a low metabolic rate which increases once they respond sufficiently to seasonal conditions to become reproductive. Further, when thinking about the possibility that breeding monarchs along the coast might move inland, that may only apply to newly emerged monarchs that have yet to become reproductive. From all we have been able to ascertain, once late summer monarchs become reproductive, they do not migrate even if exposed to seasonal changes that result in migration by younger cohorts. In effect, once reproductive, older adults appear to be insensitive or “blind” to seasonal cues. Mating is delayed in monarchs with most mating occurring on days 3-5 post emergence. That coincides with ovary development and the production of juvenile hormone. My guess is that the conditions experienced during these first 3-5 days determine whether monarchs migrate. If I’m correct, newly emerged monarchs that result from continuous breeding along the coast, if exposed to seasonal cues that signal migration, would do so. There is no a priori reason to expect that that would not happen. Still, there are reasons to be skeptical about whether this scenario played out last March and April. We know too little about winter breeding along the coast. We need to know the where and when new adults are produced as well as their numbers.

Some may also wonder whether conditions seen in Mexico apply to California. They probably do. The following is a summary of the first day that the SASN reaches 56 degrees in California locations along with cities in Texas and Oklahoma. These dates and latitudes are represented in Fig. 1. These comparisons suggest that, at least in terms of daylength associated celestial cues, Western and Eastern monarchs are exposed to similar conditions.

Table 1. March dates SASN reaches 56 degrees in California, Texas and Oklahoma

Date	Location 1	Location 2
17 March	San Diego, CA (32°42'56")	Dallas, TX (32°48'20")
21 March	Ventura, CA (34°15'17")	Ardmore, OK (34°9'9")
23 March	Pismo Beach, CA (35°9'12")	Okmulgee, OK (35°38'5")
27 March	Pacific Grove, CA (36°37'13")	Enid, OK (36°24'8")

Figure 1. A few monarchs from Mexico appear to reach Texas during the first week of March when the SASN is close to 56 degrees. As monarchs continue to arrive from Mexico and move further north in Texas and into Oklahoma, they appear to be tracking an SASN of 56 until the third week of April. By that date, most have died and there is a drop in sightings until the first-generation monarchs begin moving north in late April and May.

Conclusion

So, how can we explain the difference in the overwintering numbers from 2020 to 2021? Two things seem unlikely. It doesn’t seem possible that the few hundred females that survived from last year’s overwintering population could account for over 200,000 monarchs this year. Nor is there any evidence that monarchs arrived in the inner West in March and April from Mexico. That leaves us with the possibility that there were unfound overwintering sites with thousands, perhaps 10’s of thousands of monarchs, and the possibility that offspring of coastal breeding monarchs moved inland and generated a first generation that colonized the breeding areas in the inner West and the northwestern states. The problem is there is no evidence for either – although both may have occurred. There is at least one other approach. We can use what is known about monarch population dynamics to bracket the possible number of females it took to produce more than 200,000 adults – a lot more in fact – since we need to account for attrition during the migration. Those calculations will have to wait until we get the final numbers, but see the notes below.

Notes

*Here are a few of the details that are required to calculate population increases. First, you have to know, or estimate, the number of females at the start of a generation. Then, you need to estimate the mean number of eggs produced per female (250-350). That is followed by an estimate of the survival to the pupal stage (0.01 or more) and then the survival of pupae to adult (0.76). Since not all adults reproduce, you need another estimate of those numbers (0.85). The last multiplier is the proportion of females which is generally close to 0.45.

Here is an example calculation:

1000 x 250 = 250,000 x 0.01 = 2500 x 0.76 = 1900 x 0.85 = 1615 x 0.45 = 727. Hmmm, those numbers don’t work since you end up with fewer females than we started with. If we increase the egg to pupal survival to 0.03 we get the following.

1000 x 250 = 250,000 x 0.03 = 7500 x 0.76 = 5700 x 0.85 = 4845 x 0.45 = 2180. That yields a 2.2-fold increase. Even after 4 generations that rate of increase isn’t sufficient to generate more than 200,000 migrants.

Perhaps I’m missing something or underestimating egg numbers or survival, but if these calculations are even close, they suggest that thousands of females were required to produce this year’s overwintering numbers. That said, we haven’t accounted for the attrition during the migration made by the first generation as it moves into the inner west and the northwestern states. Two things could happen. The number of females surviving to reproduce would be reduced, and the mean number of eggs per female would decline as well, not only due to a reduction in the size of the cohort, but because the search time for host plants is likely to increase, especially in the West. If there is either a significant loss of the first-generation females during colonization or significant reduction in mean egg number, it would be difficult for the population to produce an overwintering population of >200K. The keys to population growth are the number of females at the start of each generation and, in the case of monarchs West and East, the size of the first generation and its success in reaching the main summer breeding grounds. Again, those considerations suggest that a relatively large number of females had to be involved in the establishment of the first-generation last year.

The calculations I’ve used assume constant rates of mortality from one generation to the next. However, the incidence of parasitism by tachinid flies and O. e. tends to increase as the season progresses. Such increases would reduce both the proportion of larvae reaching the pupal stage and surviving to the adult stage. In the case of the adults with O. e., their fitness to reproduce would be compromised. We also need to recognize that realized fecundity, i.e., the mean eggs per female per generation, varies with temperature, nectar availability, and the distribution, abundance and quality of milkweeds. These factors also affect population growth.

** In subsequent years, especially in 2012 and 2017, it became apparent that high March temperatures and strong southwesterly winds allowed monarchs to advance much faster than expected for SASN. It was cooler in March in Texas from 1997 to 2000 than it has been in recent years.

*** Actually, the SASN advance averages less than 69 miles per day over the entire migration, but three days per degree of latitude is a useful reference point for discussion.

Relevant literature

Altizer, S., Oberhauser, K. S., and L.P. Brower. 2000. Associations between host migration and the prevalence of a protozoan parasite in natural populations of monarch butterflies Ecological Entomology 25(2):125 – 139 DOI:10.1046/j.1365-2311.2000.00246.x

Brower, L.P. and R.M. Pyle. 2004. The interchange of migratory monarchs between Mexico and the Western United States, and the importance of floral corridors in the fall and spring migrations. In Conserving Migratory Pollinators and Nectar Corridors in Western North America, edited by G. Nabhan, 144-166. Tucson: University of Arizona Press.

Grant, T. J., D. T. T. Flockhart, T. R. Blader, R. L. Hellmich, G. M. Pitman, S. Tyner, D. R. Norris, and S. P.Bradbury. 2020. Estimating arthropod survival probability from field counts: a case study with monarch butterflies. Ecosphere 11(4):e03082. 10.1002/ecs2.3082

James, D.G.; Schaefer,M.C.; Krimmer Easton, K.; Carl, A. First Population Study on Winter Breeding Monarch Butterflies, Danaus plexippus (Lepidoptera: Nymphalidae) in the Urban South Bay of San Francisco, California. Insects 2021, 12, 946. https://doi.org/10.3390/ insects12100946

Nail, K. R., C. Stenoien, and K. S. Oberhauser. 2015. Immature monarch survival: effects of site characteristics, density, and time. Annals of the Entomological Society of America 108:680–690.

Oberhauser, K., R. Wiederholt, J. E. Diffendorfer, D.Semmens, L. Ries, W. E. Thogmartin, L. Lopez-Hoffman, and B. Semmens. 2017. A trans-nationalmonarch butterfly population model and implica-tions for regional conservation priorities. EcologicalEntomology 42:51–60.

Semmens, B. X., D. J. Semmens, W. E. Thogmartin, R.Wiederholt, L. Lopez-Hoffman, J. E. Diffendorfer, J.M. Pleasants, K. S. Oberhauser, and O. R. Taylor.2016. Quasi-extinction risk and population targets for the Eastern, migratory population of monarch butterflies (Danaus plexippus). Scientific Reports6:23265.

Taylor OR Jr, Lovett JP, Gibo DL, Weiser EL, Thogmartin WE, Semmens DJ, Diffendorfer JE, Pleasants JM, Pecoraro SD and Grundel R (2019) Is the Timing, Pace, and Success of the Monarch Migration Associated With Sun Angle? Front. Ecol. Evol. 7:442. doi: 10.3389/fevo.2019.0044

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How many hectares in 2021-2022?

6 January 2022 | Author: Chip Taylor

Each year, at about this time, I administer a test – to myself. I have one question. How big, in term of hectares*, will the overwintering population be this year? Technically, I fail the test every time and expect to. Realistically, it would be virtually impossible to correctly predict the overwintering numbers given the number of variables involved in each migration. For example, there is no way to predict the weather conditions in Mexico that determine how tightly the monarchs are clustered when measured during mid-December. There are other variables in Mexico as well – such as the density of the forest. What I’m alluding to is that a hectare in one part of the forest could represent a widely different number of monarchs from a hectare in another location. So, the bottom line is that everything is an estimate, and we don’t know how well the hectares from one year compare to those of another. While that is true, the hectare measure seems to represent the size of the population fairly well. For example, the number of monarchs tagged in the Midwest each fall is strongly correlated with the overwintering number. That would not be true if there was a lot of error in the number of hectares and the number of butterflies per hectare following each migration.

So, if the number of tagged butterflies can be used to predict the overwintering population, why don’t I just use those numbers as predictors? Unfortunately, it takes months and months to assemble all the tagging records for a given year. Therefore, I have to look to other measures or conditions and draw on the historical record to arrive at a prediction. The conditions during the spring in Texas, the recolonization of the northern breeding areas in May, the summer temperatures, the weather during the migration and the availability of nectar sources in Texas all differ from year to year and all factor into the number of monarchs that reach the overwintering sites. The challenge for me is to assess each of these conditions for a given year and to compare these outcomes with the record that goes back to 1994.

After considering all of these factors for this past season, I came up with the following estimate – 0.8-1.2 hectares. Ouch! That’s low and lower than the 2.01 hectares measured last year. In fact, if 1.2 hectares this year, that would be the lowest number since the winter of 2014-2015. I know that that is not what anyone wants to hear, and I don’t want to accept those numbers myself, but that is what my assessment tells me. My history with these estimates is fair, but I usually underestimate the size of the population which means that I’m overestimating the negative impact of one or more factors. These over and under estimates speak to my goal which is to develop a deep understanding of all the factors that determine the size of the population. Being wrong goes along with learning how to refine my estimates. Last year my estimate for the hectare total was almost spot on – 2.0 hectares vs a measured 2.01 hectares. It was more of a guess than a data-based prediction, but I’ll take credit for being close. There are reasons to think I will be close again this year and other reasons to predict that the number will be higher.

In the following paragraphs I’ll summarize the reasons for why my prediction might be right or wrong. Although I evaluate data from the entire range of the eastern monarch range, my prediction is largely based on what I can glean about the colonization and population growth that occurs from 90-100W – a region from just west of Madison, WI to the central Dakotas. Tagging results indicate that about 70% of the monarchs that reach the overwintering sites originate from this region.

There are several reasons the monarch numbers at the overwintering sites might be lower this winter than in recent years. First, as shown in the drought monitor images for this past summer (Figs 1-3), there was a severe drought in the Dakotas that extended eastward well into Minnesota. Droughts have a strong negative impact on monarch population development since plant growth is stunted, plant quality declines and nectar is more limited. These conditions decrease monarch longevity and reproductive success. High temperatures, which often accompany drought conditions, also negatively influence population growth. This year, the first sightings posted to Journey North indicated that monarchs arrived in the northern breeding areas on time and in good numbers. However, post arrival, the regional and state temperatures were substantially above the long-term averages for June through August. For example, the average temperatures were +3.1F for the Upper Midwest, +1.2F of the Ohio Valley and +2.8F for the Northeast. The temperatures in the states in the drought areas were +4.3 for North Dakota, +3.9 for South Dakota and +3.8F for Minnesota. The temperature for Minnesota was the second highest since 1895. The temperatures are significant since the record shows that populations decline when the mean temperatures exceed +2F. These above average temperatures persisted into September in the Upper Midwest and the effect was to delay the migration. Again, the tagging data shows that late migrations are associated with lower numbers reaching the overwintering sites.

As to numbers in the migration, Journey North tallies the number of roosts reported by observers. These sightings include estimates of the number of monarchs. A quick scan of these estimates suggested that the numbers for all sightings this year were about half those in 2020. The observations by Harlen and Altus Aschen near Port Lavaca, TX suggested that the flow of monarchs along the Gulf coast, many of which probably originated from the Northeast, was late and involved a relatively small number of monarchs.

In summary, all of the metrics used to assess the size of the summer and migratory populations indicated that the population reaching the overwintering sites would be substantially lower than the number measured in 2020.

There are also reasons why my estimates might be overly pessimistic. A recent report from El Rosario offered that the population this year was about a third larger than last year. Further, in early December, the counts of trees occupied by monarchs at Chincua, Cerro Pelon and Herrada were all greater than I would have expected based on my assessments. We will have to wait for the official counts. I’d be delighted to be wrong – on the low side that is.

*One hectare is equal to 2.47 acres. One acre is approximately the area of a football field exclusive of the end zones.

Figure 1. June Drought Monitor

Figure 2. July Drought Monitor

Figure 3. August Drought Monitor

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2021 year-end summary

31 December 2021 | Author: Jim Lovett

Season’s Greetings from the staff at Monarch Watch!

We would like to thank everyone who contributed to our program in the last year. That support has enabled us to maintain and grow our programs and aid many people in their efforts to create habitats for monarchs. As you know, sustaining the migration is a massive undertaking due to continuing loss of milkweed/monarch habitats. We’ve distributed over one million plants through our Milkweed Market and free milkweeds programs since 2014 but we need to do more. We expanded our efforts in California this past season and distributed about 3,800 plugs of Asclepias fascicularis, the most common hostplant used by monarchs in that state. Our ambitious goal for California in 2022 is the distribution of at least 36,000 milkweed plugs. We will be working with other non-governmental organizations as well as state and federal agencies to find homes for these milkweeds.

Although adjustments to Covid-19 continued with the cancelation of our Spring and Fall Open House events this year, we were able to hold our fall tagging event at the Baker Wetlands to the delight of many families. We had a wonderful day in the great outdoors and there were smiles all around.

The newly developed Monarch Watch mobile app will make it easier for many taggers to record butterflies as they are tagged and submit data electronically. The beta testing of the app has gone well, and we hope to launch it for general use during the 2022 tagging season. We will have much more to say about this in the coming months. As we mentioned last year, two papers have been published recently on the results of the tagging. The data analysis is continuing and two additional papers are well underway. It’s a slow process – lots of data!

This past year, to expand our ability to distribute more milkweeds for restoration projects, we worked closely with the KU Endowment Association to raise funds through the annual “One Day. One KU.” campaign held in February. Hundreds of people responded with contributions sufficient to enable us to distribute an additional 28,000 milkweed plugs and clearly demonstrated the widespread support for monarch and pollinator conservation.

Time flies when you are having fun and that’s also true if you have a vision and a mission and are driven to see it through. That may be fairly said of the Monarch Watch team. Although we often wondered if we would survive financially from one year to the next, Monarch Watch continued to grow and will be celebrating 30 years of education, conservation, and research in 2022! We are not yet sure how we will mark this milestone, but there will certainly be a retrospective component and maybe an event or two. We will keep you informed via our blog, email updates, and social media.

Again, thank you for your continued support and we hope you will be with us again this coming year. Best wishes to you and yours for a happy and healthy holiday season. Please stay safe!

Sincerely,

Chip Taylor, Jim Lovett, Ann Ryan, Angie Babbit and Dena Podrebarac
Team Monarch Watch

To keep up with the status of monarchs and other news, subscribe to our email updates ( monarchwatch.org/subscribe ), join our email discussion list ( monarchwatch.org/dplex ), visit our blog ( monarchwatch.org/blog ) and follow us on Facebook, Instagram, and Twitter.

Monarch Watch
Kansas Biological Survey & Center for Ecological Research
University of Kansas
2021 Constant Avenue
Lawrence, KS 66047
785-864-4441
monarch@ku.edu
monarchwatch.org

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Monarch Watch Update August 2021

23 August 2021 | Author: Jim Lovett

Greetings!

Included in this issue:
1. Monarch Population Status
2. Monarch Watch Tagging Kits
3. Submitting Tag Data
4. Chip in for Monarch Watch
5. Monarch Waystations
6. Upcoming Monarch Watch Events
7. About This Monarch Watch List

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1. Monarch Population Status —by Chip Taylor
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The migration is underway!

EASTERN MONARCHS
As you may remember, earlier I offered that the recolonization this past May and early June of the summer breeding area was quite favorable. Monarchs generally arrived on time and in good numbers leading to a large second generation. Things looked favorable for a large migratory population that could rival that of 2018 (6.05 hectares) – provided that the summer temps were within 2F of the long-term average and that September temperatures in the north were generally normal as well.

I have been following the weather closely for the last several months and things still look good for a large migration over most of the summer breeding area. However, I have doubts about the number of monarchs that will join the migration from the eastern Dakotas and western Minnesota. Portions of that region have been much warmer and drier than is generally ideal for monarch population development.

In contrast, due perhaps to adequate rainfall and moderate summer temperatures, monarchs are much more abundant in Oklahoma and Texas at this time, suggesting that high numbers of monarchs could join the migration from this region in late September and October. The September temperatures are still a question, but there is no evidence of a drought in Texas or elsewhere that might diminish the possibility of surviving the passage to the overwintering sites.

Overall, while the conditions for population growth have been less favorable than in 2018, suggesting an overwintering population of less than 6 hectares, there is every reason to expect a larger overwintering population in Mexico this year than seen during the last two winters (2.83 hectares for 2019-2020 and 2.10 hectares for 2020-2021).

WESTERN MONARCHS
Given the winter, spring, and summer monarch numbers as well as the extreme summer temperatures and drought conditions in the West, the prospects for an overwintering population of more than a few hundred monarchs along the California coast appear to be slim at best.

For those who would like to delve deeper into the timing, pace and duration of the monarch migration, please see a recent post to the Monarch Watch Blog (https://monarchwatch.org/blog): “Some notes on the sun angle at solar noon (SASN) and the passage of the migration”

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2. Monarch Watch Tagging Kits
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We are in the process of sending out tagging kits for our 30th tagging season – wow! As of today, all preorders and most recent orders going to locations north of (and including) Colorado, Kansas, Missouri, Kentucky, and Virginia have been mailed out. If you are located in that area and you have not yet received your tags, watch your mail for them to arrive within the next 10 days or so. Tags for locations further south will be mailed out soon – priority is always given to those tag orders going to locations that will experience the migration first.

Monarch tagging continues to be an important tool to help us understand the monarch migration and annual cycle – a long-term record is crucial to understand the dynamics of such complex natural phenomena. If you would like to tag monarchs this year, please order your tags soon as they are going fast! Tagging Kits should arrive within 10–12 days but as mentioned above, priority will be given to areas experiencing the migration first.

Monarch Watch Tagging Kits are only shipped to areas east of the Rocky Mountains. Each tagging kit includes a set of specially manufactured monarch butterfly tags (you specify quantity), a data sheet, tagging instructions, and additional monarch / migration information. Tagging Kits for the 2021 season start at only $15 and include your choice of 25, 50, 100, 200, or 500 tags.

2021 datasheets and instructions available online via the Monarch Tagging Program page at https://monarchwatch.org/tagging

Tagging should begin in early to mid-August north of 45N latitude (e.g. Minneapolis), late August at other locations north of 35N (e.g., Oklahoma City, Fort Smith, Memphis, Charlotte) and in September and early October in areas south of 35N latitude. See a map and a table with expected peak migration dates on the Monarch Tagging Program page at the link above.

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3. Submitting Tag Data
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Thousands of you have submitted your recent tag data to us by mail or via our online submission form – thank you! We are still receiving data sheets and if you haven’t submitted your data yet (for 2020 or even previous years) it is not too late. Please review the “Submitting Your Tagging Data” information on the tagging program page then send us your data via the Tagging Data Submission Form. For 2021, please submit your data soon after you are finished tagging for the season.

Complete information is available at https://monarchwatch.org/tagging if you have questions about submitting your data to us and we have conveniently placed a large “Submit Your Tagging Data” button on our homepage at https://monarchwatch.org that will take you directly to the online form.

There you can upload your data sheets as an Excel or other spreadsheet file (PREFERRED; download a template file from https://monarchwatch.org/tagging) or a PDF/image file (scan or photo).

If you have any questions about getting your data to us, please feel free to drop Jim a line anytime via JLOVETT@KU.EDU

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4. Chip in for Monarch Watch
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Our “Chip in for Monarch Watch” fundraising campaign was created in honor of our director and founder, Chip Taylor (whose birthday happens to be at the end of August, by the way). This campaign offers a chance for Monarch Watchers, colleagues, friends, and family across the planet to show their support for Chip and the Monarch Watch program he brought to life more than a quarter-century ago. It has provided tremendous support for Monarch Watch over the years, through both monetary contributions and kind words.

We encourage you to spend a little time reading through previous donor comments on the Chip in for Monarch Watch page (https://monarchwatch.org/chip) – the connections that are facilitated by monarchs and Monarch Watch are truly extraordinary.

The 2021 Chip in for Monarch Watch fundraising campaign is now underway! If you are in a position to offer financial support to Monarch Watch (or know someone who might be), please consider making a donation of any amount during this campaign.

Here’s how it works:
1. Donate online via KU Endowment: https://kuendowment.org/monarch (offline options are also available, see below)

2. Submit your pledge, comments, thanks, birthday wishes, photos, etc. for Chip: https://monarchwatch.org/chip/submit

3. We will assemble a donor list, comments, and photos to present to Chip at the end of the campaign.

Donating securely online is easy but if you would rather make a donation by phone or mail please see complete details at https://monarchwatch.org/chip/

Thank you!

Chip in for Monarch Watch: https://monarchwatch.org/chip

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5. Monarch Waystations
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To offset the loss of milkweeds and nectar sources we need to create, conserve, and protect monarch butterfly habitats. You can help by creating “Monarch Waystations” in home gardens, at schools, businesses, parks, zoos, nature centers, along roadsides, and on other unused plots of land. Creating a Monarch Waystation can be as simple as adding milkweeds and nectar sources to existing gardens or maintaining natural habitats with milkweeds. No effort is too small to have a positive impact.

Have you created a habitat for monarchs and other wildlife? If so, help support our conservation efforts by registering your habitat as an official Monarch Waystation today!

https://monarchwatch.org/waystations

A quick online application will register your site and your habitat will be added to the online registry. You will receive a certificate bearing your name and your habitat’s ID that can be used to look up its record. You may also choose to purchase a metal sign to display in your habitat to encourage others to get involved in monarch conservation.

As of 4 August 2021, there have been 35,768 Monarch Waystation habitats registered with Monarch Watch! Texas holds the #1 spot with 2,922 habitats and Illinois (2,789), Michigan (2,662), California (2,319), Ohio (1,863), Florida (1,788), Virginia (1,602), Wisconsin (1,570), Pennsylvania (1,557) and Ontario (1,179) round out the top ten.

You can view the complete listing and a map of approximate locations via https://monarchwatch.org/waystations/registry

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6. Upcoming Monarch Watch Events
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Monarch Watch Fall Open House
Event Canceled 🙁
Lawrence, Kansas

We had hoped to be able to welcome you back to our Fall Open House event, but we are all going to have to wait a bit longer – sorry! We invite you to visit our garden and enjoy our outdoor space on your own this fall. Evenings and/or weekends would be the best time to visit given the parking restrictions on campus. Thank you for your interest and we hope to see you in person soon. Stay safe!

Monarch Watch Tagging Event (Free event)
Saturday, September 18, 2021
Baker Wetlands Discovery Center
Lawrence, Kansas

The tagging has always been an outdoor event so we are still planning to host it in cooperation with the Jayhawk Audubon Society and the Baker Wetlands Discovery Center – it should be similar to previous years. If you’ll be in the Lawrence, Kansas area in September, we’d love for you to join us so mark your calendars and stay tuned to our website, emails and social media for updates.

Complete details: https://monarchwatch.org/tag-event/

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7. About This Monarch Watch List
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Monarch Watch (https://monarchwatch.org) is a nonprofit education, conservation, and research program affiliated with the Kansas Biological Survey & Center for Ecological Research at the University of Kansas. The program strives to provide the public with information about the biology of monarch butterflies, their spectacular migration, and how to use monarchs to further science education in primary and secondary schools. Monarch Watch engages in research on monarch migration biology and monarch population dynamics to better understand how to conserve the monarch migration and also promotes the protection of monarch habitats throughout North America.

If you have any questions about this email or any of our programs, please feel free to contact us anytime.

Thank you for your continued interest and support!

Jim Lovett
Monarch Watch
https://monarchwatch.org

If you would like to receive periodic email updates from Monarch Watch, you may SUBSCRIBE via https://monarchwatch.org/subscribe

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Some notes on the sun angle at solar noon (SASN) and the passage of the migration

17 August 2021 | Author: Chip Taylor

Linking the timing, pace and duration of the migration to the sun angle at solar noon (SASN) was only possible because thousands of volunteers tagged monarchs from the time monarchs emerged in late summer until the end of the migration. We now know that the migration begins when the SASN drops below 57 degrees over all latitudes with the monarchs reaching the overwintering latitude in Mexico when the SASN also has dropped below 57 degrees. We also know how the composition of the migration changes from the beginning to the end of the migration and much more.

My intention with this text is to provide you with a better understanding of how the migration is related to SASN and how you can acquire these values for your location and dates of tagging.

The migration lasts 25-33 days in most locations. That means there is a beginning or leading edge (that can either be awesome or a trickle) a peak or midpoint, which usually contains a large portion of the migrants, and an end, which is modest in most years and dominated by smaller monarchs, of which a high proportion are females (relative to earlier in the migration).

The SASN values that correspond to these phases of the migration are as follows.

Leading edge – SASN less than 57 degrees to 54 degrees

Mid-point – SASN from 53-50 degrees

End – SASN 49-46 degrees

For reference, each SASN degree represents a little less than three days. However, that relationship varies slightly with latitude.

It helps to keep in mind that while the above SASN values represent “average rates of movement” of the migration, the migration advances more slowly when it’s too cold, too hot, too rainy or too windy.

To calculate the SASN for a specific latitude and date, go to suncalc.org.

I entered Lawrence, KS, USA. Then clicked on culmination to get the correct SASN value for today. After that I opened the tool box indicated by T and clicked on date slider to open that feature. Once that was open, I closed the tool box. The slider allows you to change the dates easily.

The first image shows the SASN – 64.52 (Altitude in the column at the left) for Lawrence, KS for today 16 August – and the second shows the SASN for the 7th of September – the first day that the SASN drops below 57 degrees (56.81 degrees) for this latitude (N 38°58’23.05”). This date is the earliest date we might expect to see the arrival of migrants from the north in Lawrence. The migrants can be distinguished from non-migratory monarchs, that is those that are still reproductive, since they exhibit directional flight with a distinct heading. In our area, the mean heading for migrants is 210 degrees.

As mentioned, it is only because monarchs have been tagged from the time they emerged in late summer until the end of the migration and beyond that we have been able learn how the migration functions. Given the changing climate which appears likely to affect the migration more and more in coming years, it’s important for taggers to continue the practice of tagging monarchs from emergence of the last generation until the last monarchs pass through each latitude.

Screenshot images from suncalc.org:

Image 1.

Image 2.

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Monarch Population Status

17 August 2021 | Author: Chip Taylor

The migration is underway!

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Monarch Population Status

Monarchs, milkweeds and O. e.: It’s time for a more holistic approach

Monarch Watch Update February 2022

Monarch Watch Update January 2022

Western Monarchs

How many hectares in 2021-2022?

2021 year-end summary

Monarch Watch Update August 2021

Some notes on the sun angle at solar noon (SASN) and the passage of the migration

Monarch Population Status

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