Why monarchs are an enzyme – Part 2

See Why monarchs are an enzyme – Part 1 posted earlier this month.

What the heck is realized fecundity/fertility and why is it important?

A term I mention from time to time in my talks is realized fecundity. Add to that, I might mention fertility, reproductive success and age to first reproduction. I first encountered these terms when taking an ecology course in graduate school in the late 1960s. There was a unit in the course that dealt with demography – birth and death rates, stable age distributions and factors leading to declines or growth of populations. Among these lessons were a few exercises designed to inform the students of factors that most strongly influenced population growth. The two that stood out were realized fecundity and age to first reproduction. Both are key to understanding population growth in monarchs and inter-annual variations in the sizes of the population at the end of the growing season.

When assessing population growth, the focus is on females. Each monarch female has a potential to produce offspring – a maximum number of eggs that could be laid given the size of the female, the fat body carried over from the larval stage, it’s inherent fitness as defined by its genes, etc. Total lifespan is a factor as well. There are only so many wing beats and degree days per life time. These are all intrinsic factors, that is, properties of each female. Realized fecundity deals with extrinsic factors that have the effect of limiting the number of eggs laid by a female in her lifetime. The list of extrinsic factors is long and involves both physical factors such temperature, precipitation, and wind speed as well as biological factors that include plant quality, nectar availability, number of and fertility of mates, predators, etc. In addition, we need to consider that there may be a cost in terms of eggs not laid due to search time required to find suitable host plants and nectar sources. Search time involves habitat fragmentation which I may get to in other posts.

A basic tenant of population growth is that populations with a short age to first reproduction grow faster than populations in which reproduction is delayed. When talking about monarchs, age to first reproduction can be defined as the interval from when an egg is laid until a female that has developed from that egg lays her first egg. That interval can be as short as 30 days (4 egg, 12 larva, 10 pupa, 4 mating to first egg) and at least as long as 50 days in the spring. This range is due to differences in the temperatures experienced throughout the developmental period. In other words, the temperatures experienced throughout development determine age to first reproduction. As we will see, the distribution of eggs across the latitudes in the spring has a big role in determining age to first reproduction and therefore population growth.

While I used the potential egg laying capacity of individual females to introduce this topic, we need to consider females as a group or cohort to determine the impact of extrinsic factors at the population level. So, what are the conditions that would enable a cohort of females to achieve a high-level egg laying or, conversely to reduce egg laying? I’ve examined the weather conditions during the annual cycle for the eastern monarch population for every year since 1994. That analysis has yielded lists of factors that favor and do not favor monarch population growth (Tables 1 and 2). As you go down the list in each of these figures, you will note that a number of the factors listed, such as winter mortality or survival as monarchs migrate north from the overwintering sites into Texas in March, have to do with losses that ultimately define cohort size. Some unknown portion of that mortality may be due to the condition of the butterflies that arrived at the overwintering sites in the fall. For example, butterflies that experienced drought, either during development as a larva or during the migration itself, are more likely to die during the winter and migration north than butterflies that developed and migrated under more favorable conditions. Further, it is probably the case that the potential reproductive capacity of female cohorts arriving in Texas varies from year to year. It should be noted that both nectar and water availability during both the winter and the spring exit from Mexico play a role in survival during these periods.

Table 1. Optimal conditions for population growth.

Table 2. Negative conditions.

Once the cohort of returning monarchs reaches the milkweed rich areas of Texas (12-15 March), realized fecundity and age to first reproduction becomes important. Conditions favoring egg laying include temperatures that are less than -1.5°F below the long-term average, abundant emerging milkweeds, adequate nectar and water, moderate winds and relatively low precipitation from 15 March to 15 April. The lower than average temperatures extend the life of the females (lower number of degree days) but also have the effect of limiting northward movement. The net effect of lower temperatures is that most eggs are laid in Texas and southern Oklahoma where it is relatively warm allowing the immatures to grow rapidly – thus reaching reproductive age in a minimum number of days. In contrast, with warmer temperatures females continue moving north laying their eggs at latitudes with cooler temperatures. The effect is to produce offspring with longer ages to first reproduction at these latitudes and to increase the average age to first reproduction for all offspring produced by the cohort arriving from Mexico. The importance of where eggs are laid by returning females and age to first reproduction is supported by the observation that in all four years with mean temperatures of less than -1.5°F for March in Texas, the populations grew from one year to the next. However, the populations declined in 9/11 years during which temperatures were greater than 1.9°F above the mean. One of the two years with high mean March temperatures in which the population increased was 2018 (+5.4°F). In other years with similar high temperatures, the returning monarchs moved northward into Oklahoma, Kansas and sometimes Nebraska, but not in 2018. This unusual dynamic was due to a low that settled over north Texas and southern Oklahoma in late March. Temperatures were low enough during this period to keep monarchs confined to central Texas well into April*. Thus, egg laying was largely confined to Texas where warmer than average temperatures accelerated the development of the immatures. The result was a large cohort of first-generation monarchs that migrated northward in May, a cohort with a low and therefore favorable age to first reproduction. This combination of warm conditions favoring rapid development of immatures yet cold that largely restricted egg laying to Texas in March and into early April has only occurred once since 1994. Yet, it was one of the major factors that contributed to the increase in monarch numbers from 2017 (2.48 hectares) to 2018 (6.05 hectares).

Up to this point I’ve just hinted at how realized fecundity can be modified by extrinsic factors. Let’s consider drought, high temperatures and extended periods of rainfall. There are other factors, but these cases will provide examples of how deviations from optimal conditions can influence population growth.

Summer droughts affect monarchs, nectar sources and host plants. Monarchs need water which is usually obtained from nectar or dew during the summer, and both are scarce in droughts. In addition, monarchs need the carbohydrates (and amino acids) found in nectars to fuel flight, egg development and egg laying, etc. Lack of water and nectar can result in fewer eggs laid and even shorten life span for a reproductive cohort. Higher than average temperatures (>+2°F) can have similar effects. Plants develop faster resulting in shorter flowering intervals, often with lower nectar production and more rapid senescence, the latter making the milkweeds less attractive to females for oviposition. Again, adult life span is reduced at higher temperatures. Rainfall, if prolonged over several days, or any weather that restricts flight and egg laying for a number of days, also reduces realized fecundity. There are only so many degree days in the life of an adult monarch (530)**, time is ticking, and, as pointed out in Zalucki and Rochester (2004), there is no recovery from lost opportunities to lay eggs.

If you have been able to follow this tutorial, it should be apparent how deviations from optimal conditions in terms of realized fecundity are the basis for the stage-specific model I’ve mentioned in previous posts to this Blog. But, it’s not the only factor. We need to consider reproductive success as well. Beyond that, we need to discuss how populations recover from a series of negative conditions that have significantly reduced the size of reproductive cohorts.

*Although the optimal temperatures that allow returning monarchs to move northward are not known, it’s clear that advances are limited when temperatures are less than 70°F.

**The estimated number of degree days (530) represents a life span of roughly 3-4 weeks for reproductive monarchs under average summer conditions (Zalucki and Rochester, 2004). Longer life is possible during periods with daytime temperatures in the 60s. Shorter life spans are expected when temperatures exceed 90°F.

Reference
Zalucki, M.P. and W.A. Rochester. 2004. Spatial and temporal population dynamics of monarchs down under: Lessons for North America. In The Monarch Butterfly: Biology and Conservation, eds., Oberhauser, K. S. and M.J. Solensky. pp. 219-228.

Give to Monarch Watch today via One Day. One KU. fundraising campaign

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Your generous support today via the University of Kansas’ One Day. One KU. fundraising campaign will help us restore habitat for monarchs and other native pollinators. Specifically, your donation will be used to:

• administer free milkweed grants to schools and nonprofits

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• provide milkweed plants for large-scale restoration projects

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Grasslands, birds, monarchs, pollinators and more

The world has been changing rapidly, but the changes are such that most of us aren’t aware of what has changed or what is missing.

As an ecologist, I’m alert to change but, like most people, I often miss the indicators. Crows are down. The numbers aren’t what they used to be. Did you notice? I did but well after I should have. Crows and other corvids declined due to their susceptibility to West Nile Virus. I anticipated that the numbers would recover once the virus had run its course. They did, somewhat, but the numbers are not what they were before West Nile, and now they may be declining for other reasons.

What about other birds? Did you catch the headlines in September announcing the results of a study of bird population numbers in the United States over the last 50 years? The numbers have declined by 29% or 2.9 BILLION birds! The biggest losses, a negative 53% (>700 million) occurred, in 31 grassland species. Wow! That’s staggering, and these results give rise to many questions. Why were the losses highest across the vast grasslands that dominate areas east of the Rockies in the United States and Canada to eastern Illinois? What factors contribute to these losses? Probable causes include loss of habitat, fragmentation, neonic insecticides, herbicides and mowing. Of these, there are data on habitat loss due to the intensification of land use in agriculture and the continuous march of development. While it is likely that the other factors contribute significantly to habitat loss and losses of specific species, attaching specific numbers or even assessing which is the most important isn’t possible at this time.

Land use changes have been hard to track often resulting in long lags in reporting. Recently, the urgency of knowing what is happening in real time has resulted in more rapid updating providing us with a better measure of conversion rates each year. The impact of the Renewable Fuel Standard (RFS) on land use was a shocker. The publication of a report entitled “Plowed Under” by Faber et al. in 2012 indicated that nearly 24 million acres, an area nearly the size of Indiana, had been converted from one land use classification to another from 2008 through 2011. Subsequently, Lark et al (2015) showed that 77.7% of that acreage involved the conversion of grassland to cropland. Another report from the Lark team in 2018 indicated that over 10 million acres of grassland had been converted to crops from 2008-2016. The Plowprint Report by the World Wildlife Fund in 2018 indicated that another 1.7 million acres were converted to cropland in 2017. The bottom line is that grasslands are being lost at an average rate of more than a million acres per year.

What is less clear is how much habitat is being lost to development in grasslands. It’s probable that these losses are also in the range of a million acres a year. Further, some losses may not be accounted for. In many areas in the Midwest, growers have reduced the distance from the edge of the field to the edge of the road, leaving only low diversity grass filled margins.

There is no doubt that the grasslands are in decline and we are losing birds, but does it matter? It does. The loss of grasslands signals that we are not only losing birds, but also pollinators, monarch butterflies, small mammals and the raptors and other predators that feed on them. Further, without the pollinators, we will lose both plant and insect diversity further eroding the connections that sustain these ecosystems.

Do we want to live in a world without birds and pollinators? The larger question may be, can we? These ecosystems support us. We are dependent on the richness of these environments. The soil is alive. It’s a matrix that supports a complex web of life, and the organisms within it are often connected intimately with the health and well-being of the plant and animal life above. These connections are destroyed or modified through changes in land use and the addition of chemicals in the form of fertilizers and short and long-lived insecticides and herbicides. It’s fair to ask if, collectively, we know what we are doing. What will be the costs of our quest to extract everything we can from grasslands? Is there another dust bowl in our future?

To counter our destructive tendencies, there is a strong movement to restore habitats both broadly and for specific species. The bird study shows that, in contrast to the general decline, waterfowl numbers have increased over the last 50 years. So have eagles, peregrine falcons and a few other species. These successes are due to habitat restoration and protection. There are also attempts to restore grasslands. The challenge is massive. To keep pace with the annual rate of loss, we need to restore more than a million grassland acres a year. That requires dollars, seeds, locations, boots on the ground and more.

Can we maintain or even increase that rate of restoration? Surely, we can. Will we, is the question. I deal with this issue on a regular basis. Monarch numbers have declined by about 80% over the last two decades, and the crash in the population during the winter of 2013–2014 led to a petition to the Department of the Interior to declare the monarch a threatened species.

At Monarch Watch, we have made it our mission to do what we can to sustain the monarch migration. This mission involves getting people, businesses, states and federal agencies to plant milkweeds, the host plants of monarch caterpillars. The task is immense. A major study indicated that 1.4 BILLION milkweed stems need to be planted, mostly in the Upper Midwest, to restore monarch numbers to a level sufficient to buffer the population in the event of extreme losses due to winter storms and other weather events.

We have made a small dent in this number. To date, over 27,000 Monarch Waystations, generally small gardens or restoration sites containing milkweeds and nectar sources, have been created and registered. In addition, working with nurseries, we have facilitated the production and distribution of a million milkweed plugs (small plants) for restoration projects throughout much of the United States. Monarchs are a gateway species. They have charisma and are known to the public, and the public is strongly interested in monarch conservation. By saving the monarch migration through the restoration of grasslands we will save many other species. It’s our mission, but all can contribute. Plant milkweed!

—
This article was also published in the recent Winter 2019 Wild Ones Journal (Vol. 32, No. 4, pp 26–28).

Why monarchs are an enzyme – Part 1

Monarchs are an enzyme or rather a complex set of enzymes that interact with the physical environment in a deterministic manner. In this article, I’m going to argue that the responses of monarchs to physical conditions are determined by their genetic code which defines metabolic processes that are mediated by enzymes and biocatalysts that respond in predictable ways with the physical environment. Enzymes, as you may recall, are mostly proteins that mediate reactions with substrate molecules yielding products that mediate cellular and metabolic processes that sustain life. These processes are rate-limiting which means they are a product of the quantities of the enzymes, the substrates and temperature (and sometimes pH). Since insects, and most invertebrates, are cold blooded, with few exceptions, it is the ambient temperature that governs these reactions and ultimately the responses of the organisms to the physical conditions.

Specifically, I’m forwarding the view that an understanding of the range of responses by monarchs to a variety of conditions will help us understand and predict the inter-annual variation in monarch numbers. While the following may be obvious to some readers, conversations with colleagues suggest that many do not understand or agree with my interpretations. That said, hear me out and see what you think.

The underlying thesis is that the monarch’s DNA defines a set of limits and optima for each monarch as it interacts with the physical and biological environment. I wasn’t great at biochemistry but was impressed by enzyme kinetics and all the cascading results. Enzymes mediate chemical interactions deterministically, and in simple laboratory systems in which quantities of the interacting components are held constant, it is clear that each reaction is defined by temperature and pH with a lower limit or zero point at which no reaction is catalyzed, a rise in activity as temperatures increase, an optimal temperature for interaction with the substrate and then a decline as temperature increases even further to an upper limit where again reaction with the substrate reaches zero (Fig 1).

Figure 1. A generalized enzyme activation curve. The degree day model for the development of monarch larvae developed by Zalucki (1982) indicates a developmental zero of 11.5°C (52.7°F) at the lower extreme, an optimal temperature of 29°C (84.2°F) and an upper developmental zero of 33°C (91.4°F).

Living systems are complex with lots of enzymatic interactions having different optima and with lots of complex rate limiting interactions as well but, in my view, within the organism, all these interactions are deterministic as opposed to stochastic or random*. If you are with me so far, the argument is that the DNA driven and limited biological engine represented by the monarch functions at rates determined by temperature, light, sometimes humidity, and more rarely the composition of the surrounding gases. There are biological factors such as host plant quality, predators, pathogens and parasites to consider, and all of these respond to physical factors as well. Overall, the response to physical factors, particularly temperature, by all the biological components of the monarch ecosystem appears to be the driver that broadly determines monarch breeding success during a given year. In effect, they determine realized fecundity, a subject that I’ll deal with in Part 2.

It follows that to fully understand inter-annual variation, and to sort out the effects of biological factors, we need to define the deterministic properties of the monarch system. We can call them physical windows within which the organism functions – as an example, imagine a range of temperatures with death due to freezing at one end and death due to extreme heat at the other. Monarchs function between these limits. There is a lower limit for growth and upper limit for growth. These limiting temperatures are known as developmental zeros. For caterpillars, the low point is 11.5°C (52.7°F) and the high point is 33°C (91.4°F). At either of these extremes, caterpillars stop feeding and the metabolic system slows down. If these temperatures are maintained for long periods, the caterpillars will run out of the enzymes, metabolites and blood sugars necessary to keep the systems going and will die. There is an optimal temperature for growth as well. If we find a fifth instar caterpillar in the wild, we can estimate how long it has been a caterpillar, if we know the temperatures the caterpillar has experienced over the last two weeks or more. The calculation is based on a degree day model which, to me, is effectively an enzyme kinetic model. What I’m arguing is that we extend the degree day model to all of the other physical factors to which monarchs are exposed.

Example windows include an ambient light window, a temperature window (for all flight and for the migration specifically – and they are different), a wind speed and direction window (again with variation depending on reproductive vs migratory status), a thermal window for gliding and soaring, an oviposition window, a mating window, an e-factor window (polarization) and a few more.

Basically, we need to know how monarchs spend their days under a variety of physical conditions – the window (time, temp, light, etc.) for oviposition would be one of my first targets. I want to understand the optimization functions in the system.

Over the last 10 years or so I’ve spent many hours trying to assess the impact of physical factors on the yearly growth of the monarch populations. We focused mostly on temperature and the regressions indicated there were strong associations between temperatures in Texas in March and April and the development of the population each year. However, the regressions only explained about 40% of the year to year variation. Clearly, there was something missing. I eventually realized that mean temperatures, or rainfall, or drought indexes, were only surrogates for what was really happening. After plotting data for yet another regression, I recognized that the outcome represented an optimizing function rather than a linear relationship, and that we needed to understand the system in terms of a series of linked optimizations. Once that became clear, it was evident that, if we knew the optima for a variety of factors and could associate those with monarch specific distributions and reproductive output, we could derive a predictive model to explain monarch numbers both regionally and for most of the eastern monarch population. I have been using a crude optimization model for the last several years to predict the population trends. Some of my predictions based on this approach have been short of my expectations and others have been on the mark. It’s an iterative process of learning from my mistakes and successes.

There are many more aspects to this theme such as how this interpretation relates to behavior of individuals with specific genotypes, realized fecundity, population crashes and perhaps even to the insect apocalypse. I’ll provide additional explanations and examples in Part 2.

Here is a departing observation: in 9/11 years during which the mean temperature for March in Texas was greater than 1.9°F above the long-term average the population declined. However, for each of the 4 years with March mean temperatures <-1.5°F, the population increased. What did enzymes and optimization functions have to do with those outcomes? Plenty, as I will explain in Part 2. [Edit: Why monarchs are an enzyme – Part 2 is now online.]

*Monarch populations are defined by stochastic events to be sure but, I will argue that much of the mortality experienced during many of these events is determined by genetic limitations.

Reference

Zalucki, M.P. (1982), TEMPERATURE AND RATE OF DEVELOPMENT IN DANAUS PLEXIPPUS L. AND D. CHRYSIPPUS L. (LEPIDOPTERA:NYMPHALIDAE). Australian Journal of Entomology, 21: 241-246. doi:10.1111/j.1440-6055.1982.tb01803.x

Monarch Population Status

Why overwintering monarch numbers will be lower this year

I’ve had an answer in mind for weeks. It’s been dogging me. The question that’s the basis for this answer has many parts, and not all the parts have come together. It’s as if the answer is disconnected from the question. Some of you will remember Johnny Carson’s skits featuring “Carnac the Magnificent”. In the skit, Ed McMahon hands Carnac a succession of envelopes. Upon receiving each, Carnac holds the envelope to his forehead and announces an answer to the question sealed in the envelope. Carnac then tears open the envelope and reads a silly question that fits an off the wall answer. The absurdity of having an answer before knowing the question was great fun because life seldom works that way. When it comes to monarchs, the questions usually come first. In this case, my answer came first, and the task at hand is to determine if the many part question fits the answer, or not. And so it is with my attempts to predict the size of the overwintering population. It’s a process, part intuition and part data with an emphasis on the later. I’m sparing you the raw data in this account.

As I’ve mentioned in previous posts to this blog, I’m developing a stage-specific model that will allow me to predict the approximate size of the fall migration and the overwintering population. The model has 6 stages: 1) overwintering, 2) the return migration from the colonies to Texas, 3) reproduction by returning monarchs in March and April, 4) the migration north of the first generation in May and early June, 5) the growth of the population during the summer months and 6) the fall migration which I break up into three temporal/latitudinal segments. In addition, I consider regional monarch production, droughts, storms, and other weather events. Having put all of these measures and estimates together, I can tell you two things with certainty – I will be both right and wrong. I will be right about the size of the overwintering population relative to that of last year (6.05 hectares). The number this year will be lower. That’s been clear since late March and early April. I’ll explain why it will be lower below. The question I’ve been wrestling with is how much lower will the number be this winter. That’s where I’ll be wrong. I’ll never hit that number precisely. There are too many variables. The goal is to test the data and the assumptions with an estimate of the total area occupied by overwintering monarchs. The presumption is that, in time, as the model becomes more refined, the predictions will become more accurate. Similar models have been developed to predict salmon and waterfowl numbers.

To answer the question “How big will the overwintering population be this winter?” we need answers to many additional questions associated with the different stages and other factors. While not as large as last year, 4.7 is still a good number relative to the recent past. If I’m correct, 4.7 will be the second highest number of hectares since 2008. Although there is a lot of uncertainty in this estimate due to the lack of data on critical measures, it is likely that the area of trees occupied by monarchs will be between 4.3 and 5.3 hectares and will still be the second largest population since 2008. In the following text, I will provide a brief, somewhat sketchy, account of what has happened between the last migration and the one that is just finishing as monarchs continue to arrive at the overwintering sites.

Stages 1 & 2: Overwintering and the migration north from the colonies to Texas
The migration in 2018 was the best since 2006, and the conditions favoring population growth were probably the best since 2001. The weather conditions during the migration were excellent with abundant nectar along the entire migratory route. Texas, which experienced the rainiest September on record, was particularly rich with flowers and therefore nectar when the migration reached those latitudes in October. The last stages of the migration were delayed both in Texas and Mexico due to cold and rainy weather, and the monarchs first appeared at the overwintering sites about a week later than expected based on long-term records. Although the late fall and early winter conditions were said to be a bit warmer than usual, there were no events that appear to have contributed to higher than average winter mortality. In short, the monarchs wintered well. In March, or perhaps the last few days of February, monarchs began moving north toward Texas and the southern U.S. That return also went well with residents of Texas reporting a large number of first sightings to Journey North in March and April. At this point, I’m going to digress into a series of comparisons of the conditions during each stage for both 2018 and 2019 to illustrate why I’m predicting a lower number for the winter population in 2019-2020.

Stage 3: Reproduction by returning migrants in March and April in Texas and the South Region
Although the conditions (temperature and soil moisture) were favorable for population growth during March and April of both years, those for 2018 were better. Due to a dip in the jet stream in late March and early April, most egg laying was confined to Texas in 2018 due to the colder temperatures in North Texas and Oklahoma. Confinement to Texas resulted in a more optimal egg distribution in that it allowed a large proportion of the offspring of returning migrants to mature rapidly due to the warmer than normal March temperatures. I consider this scenario to be more optimal than having eggs distributed further north in March and early April since eggs laid at more northerly latitudes take longer to develop due to cooler temperatures. A basic principle in population biology is that populations with the lowest mean age to first reproduction grow the fastest. Although egg distribution, as inferred from first sightings, was similar in 2019, the temperatures were substantially lower in the critical developmental period resulting in a higher mean age to first reproduction than in 2018. The number of returning monarchs was higher in 2019, and more eggs and larvae may have been produced. However, this advantage could have been offset due to higher levels of fire ant predation since fire ant numbers increase following periods of abundant rainfall.

Stage 4: Migration of first-generation monarchs northward from late April to 10 June
The metric used to represent what happens during this stage is the number of days in May with temperatures above 70°F. Temperatures in this range appear to be associated with flights to the north/northeast and, using this metric, the temperatures in May allowed the population in 2018 to advance into the summer breeding area north of 40°N 7–10 days earlier than in 2019. That said, recolonization in 2019 was quite good with especially high numbers of first sightings reported to Journey North in the north central region (Michigan, Ohio, Ontario). The overall pattern of first sightings for the two years through early June is quite similar. Although the first sightings give us a picture of when monarchs reach each latitude, they don’t tell us the number of monarchs arriving at the northern latitudes. Lack of knowledge of the numbers of first-generation monarchs reaching each latitude or region limits how accurately we can predict growth of the population in June. The determinants of population growth in the northern breeding area are the time of arrival, the numbers arriving and the conditions that allow for an optimal number of hours of oviposition and larval growth. While I can’t compare the numbers arriving in the northern breeding areas in 2018 vs 2019, it does appear that the temperatures during the first two weeks in June in 2018 in the Upper Midwest were more favorable for population growth.

Stage 5: Population growth north of 40 N during June-August
The summer temperatures being 2°F higher than average in 2018 were more favorable for population growth than in 2019. In addition, the growth of the population appeared to be more widespread in 2018. In the Midwest, the highest production seemed to occur from 43–46°N in 2019 with lower than expected production from 40-43°N. From the Midwest, good production extended all the way to Maine including Ontario and parts of Quebec. Monarch numbers appeared to be higher in the Northeast in 2019 than in 2018. Comparing the size of the last generation for these two years has been difficult. While there were numerous reports of “best ever in the last xx years” there were also areas such as Iowa where the population was said to be low. Further, there was total silence about the size of the population from central Minnesota to 100°W in the central Dakotas, normally an area that produced high numbers of monarchs. I followed the number of roosts reported to Journey North almost daily for a clue as to the size of the fall population. The number of roosts were similar, but those of 2019 averaged smaller. Was that meaningful? There are many things that determine roost formation, their size and the probability that they would be observed. After wading through these mixed signals, I finally decided that the last generation and migratory population this fall was lower than in 2018 by perhaps 0.5–0.7 hectares.

Stage 6: The fall migration from early August at 50°N in Canada to 19.5°N in Mexico
The migration typically starts out slowly in the north, often moves a bit more rapidly at mid latitudes and then slows down again as it moves through northeast Mexico to the overwintering sites. It’s usually the case that, as the migration reaches each latitude, there is a wave of monarchs with large numbers the first few days or perhaps a week with monarchs still passing through for the next two to three weeks. I often characterize the migration as a standing wave with a leading crest and a long tail of perhaps 28–30 days as it progresses southward across the latitudes. This year was different. The migration was extremely slow and appeared to be stalled in southern Minnesota and Iowa day after day. We hold our Monarch Watch tagging event at a time that aligns with the peak migration at this latitude year after year. There were virtually no monarchs at the time of our event this year (21 September). They were late and didn’t arrive in our area until the last few days of September—at least two weeks late. And then, what little we saw of the migration blew through the area in a week. If I were to judge the total migration on the basis of what we were aware of passing through Lawrence, I would have to say that this migration was the smallest and weakest I’ve seen since 1992 when we started Monarch Watch. Once the migration moved through our area, it continued to progress south/southwest at a moderate pace with masses evidently moving with a weather front that passed through Oklahoma City on the 5th of October. Again, about 17 days late for that latitude. Monarchs eventually reached Texas without much fanfare about roosts, masses seen, etc. and they seemed to pass through quickly.

In summary, this migration was extremely late. The migratory population also appeared to be compressed with the majority of butterflies moving through each latitude in a matter of days with fewer lagging monarchs than seen in most years. This pattern gives rise to at least two questions: 1) what was the cause of the delay? and 2) what impact will a late migration have on the total number of monarchs reaching the overwintering sites?

The lateness can be accounted for by the higher than average temperatures over a wide area of the Midwest in September and October. Although not precisely determined, we can infer from past migrations that the optimal temperatures for migratory flight range from the mid 60s to mid 70s on days when the winds are favorable. Those conditions were rare from southern Minnesota to southern Oklahoma in September and October. In Kansas and Oklahoma, temperatures for September were the second highest for the 125 years records have been kept. The lateness of this migration is a concern since late migrations are associated with lower numbers of monarchs reaching the overwintering sites.

Another concern is the drought in Texas. Droughts are also associated with lower numbers of monarchs reaching the overwintering sites. A question during this migration is whether monarchs suffered losses given that nectar was scarce in most of Texas south of the Dallas area. Nectar is needed to fuel flight and for monarchs to build up their fat bodies. Although we don’t know whether the population suffered significant losses as it passed through Texas, they appeared to move through the state rapidly. Fortunately, the temperatures in Texas were close to the long-term average over most of the migratory areas. These temperatures allow flight as opposed to high temperatures that tend to slow the migration.

I followed the temperatures and rainfall during most of September and October for northeastern Mexico. The bottom line is that the conditions (flowering, moisture and temperature) appear to be normal for this last leg of the migration.

Ok, let’s get back to the title—”Why overwintering monarch numbers will be lower this year”. Here is a quick summary in bullet points:

Population growth
• Less than optimal egg distribution in March and April
• Later recolonization of the Upper Midwest
• Low monarch production in Iowa and maybe western portions of the upper Midwest
• Lower summer temperatures than in 2018

Migration
• Late migrations are associated with lower numbers reaching Mexico
• Droughts are associated with lower numbers reaching Mexico
• High numbers in the northeast do not translate to high overwintering numbers
• Northeast butterflies are taking too long to migrate southwest

So, there you have it—my rationale for why the population will be lower this winter than in 2018. The number will surely be higher or lower than 4.7 hectares. I hope it’s higher, but I fear it will be lower. For the record, through July, based on an early reading of the data, I predicted a population of about 5 hectares that could trend higher if the summer temperatures were above average. They weren’t.

Historic Numbers of Monarchs Seek Shelter at Roost Sites in the Lake Erie Region

Republished with permission of the Southern Lepidopterists Society

The monarch fallout which occurred during the weekend of September 7-10, 2018 was truly of historic proportion. Thousands of monarchs were reported roosting at numerous sites from Toronto to Chicago, with countless monarchs sheltering from a powerful storm at roost sites in the Lake Erie islands and along Ohio’s Lake Erie shoreline. This once-in-a-lifetime event triggered by remnants of Tropical Storm Gordon sent monarch enthusiasts squealing with delight on social media. The Nor’easter swept through the Lake Erie region during peak fall migration for the monarchs, and sent the monarchs dropping from the sky to seek shelter from the powerful winds and rain that swept through the region.

I raise monarchs from wild eggs I have collected in my northwest Ohio garden. This allows me to be better able to predict the timing and size of the fall migration in my area, based on when my wild-collected monarchs begin to eclose in September. The first week of September 2018 my wild monarchs were eclosing, and I knew peak migration was moving through my area. I carefully watched the weather, and noted the remnants of Tropical Storm Gordon moving through the Lake Erie region. I had also noted reports of large numbers of monarchs being sighted much of the summer and I knew this combination of peak migration, large population size and storm activity had the potential to create large monarch roosts at favored sites in and along Lake Erie. But nothing could have prepared me for just how spectacular this migratory event would be.

I journeyed to South Bass Island in Lake Erie with my mother and children to document the anticipated monarch roosts. We arrived at Catawba Point the afternoon of Friday, September 7th and were stunned to learn that the Nor’easter had already moved in quite fiercely, to the point that the Miller Ferry boat captains were warning passengers that they would likely be cancelling ferry service for Saturday evening and Sunday, due to 10 foot waves on Lake Erie and the storm surge created by the powerful winds. We sought the advice of friends on the island, and decided to still make the journey to South Bass Island, just 3 miles off shore. We had to leave our car on the mainland, and journeyed over to South Bass Island as foot passengers on the ferry.

We arrived on the island and my friend DJ Parker gave us his electric golf cart to use. We headed to our favorite chocolate shop and the downtown area for some lobster bisque. As we ate, I noticed only about a half dozen boats in the harbor, the place seemed empty. VERY unusual for a Friday night, and a bit concerning. I checked the radar, and noted rain was headed our way. So we finished eating and headed back to DJ’s to spend the night

Screenshot of meterorologist Ryan Wichman’s facebook page during storm (Photo by Candy)

My gut instinct told me the monarchs would be at the lighthouse grounds on the southernmost tip of the island. But I did not want to risk my family getting caught in the rain. So my family stayed at DJ’s, and I headed to the lighthouse grounds alone

As I reached the sunflower field next to the lighthouse grounds, I scanned it for monarchs. I saw 4 monarchs still feeding. It was getting a little dark due to sunset and the approaching storm. I knew the monarchs should be roosting, but I did not see any flying toward the usual spot in the trees next to the sunflower field.

CA Regional Weather Server at SFSU 8-IX-2018 satellite image of Gordon

I headed to the adjacent lighthouse grounds, parked, and stood in the driveway watching for monarchs that were flying toward the line of trees. Nothing was happening near the sunflower field. But out of the corner of my eye, through a gap in the trees, I saw 2 monarchs hovering around the other side of the trees (on the lighthouse side). They flitted along the trees, clearly looking for a roosting spot, and I followed them. They flew further down along the trees, I pursued them, and as I rounded the tree line I was greeted with hackberry and maple trees filled with clusters.

I found 1000 monarchs taking refuge at this location on the leeward side of the trees at the South Bass Island lighthouse grounds. This is the largest number I have documented at this site in 5 years, and I have never seen them roost in this particular location on the lighthouse grounds. But it was a perfect location, warm and sheltered from the sustained 20-30 mph NNE winds which were still increasing. I messaged my friend, Darlene Burgess, who does the monarch counts at Point Pelee National Park. She reported 10,000 monarchs were roosting at the tip of Point Pelee. We were excited.

I continued to observe the monarchs before me. The stable flies were biting me like crazy. I could barely stand to take pictures of the roosts.

The things one does to document monarchs.

Determined, I texted Jackie Taylor of the Lake Erie Islands Nature and Wildlife Center, and she joined me at the roosts. Her partner is a ferry boat captain, and she warned me that the ferrymen were now saying they would likely stop ferry service after just a few runs in the morning. I needed to leave the island with my family first thing in the morning, or be forced to stay until Monday.

All night I listened to the winds as my children slept.

We got up early the next morning, ate a quick breakfast, and went with DJ to the lighthouse grounds. As expected, the monarchs were still roosting just after sunrise. A few dozen monarchs would erupt from clusters in bursts to the delight of my family, but then quickly returned to the clusters.

We enjoyed them for a bit, but alas we knew we had to leave. Time was running out to get home safely…

September 8, 2018, South Bass Island monarchs roosting in maple tree (Photo by Candy)

September 7, 2018, South Bass Island, monarchs roosting in maple tree (Photo by Candy)

We arrived home, and I watched the roost reports pour in on Journey North and social media throughout the day on September 8th. DJ Parker texted me to say he had a roost of 100 monarchs for the first time ever, in the trees next to his ice cream shop’s garden near downtown Put-in-Bay on South Bass Island. Another observer on the island reported seeing 100 monarchs in a roost near Park Hotel adjacent to the downtown park. Researchers with Pelee Island Bird Observatory reported on their Facebook page that they were seeing “innumerable monarchs” on Pelee Island’s West Beach beginning 9-9-18, ultimately staying 3 days to ride out the strong winds before leaving their roosts to fly out over Lake Erie. Several observers at Wendy Park, on the Lake Erie shoreline near downtown Cleveland, OH also reported seeing 1000 monarchs roosting in the trees along the leeward side of the main woodlot and other areas of the park, remaining there through September 9th.

September 7, 2018, South Bass Island, monarchs cluster in maple tree (Photo by Candy)

Tagged monarch YUJ012 by Patrick Hogan

September 9th also saw several more reports. Steve Altic on Kelleys Island in Lake Erie reported seeing 200 monarchs at the southernmost tip of the island, roosting in a birch tree about 50 feet from the water’s edge to escape the 25mph winds. A second observer, Bryan Plonski, reported seeing at least 500 monarchs roosting on Kelleys Island from 9-9-18 to 9-10-18, on the west side of trees away from the strong NNE winds. He was delighted, reporting that he had never seen so many butterflies roosting at this site before. The Lake Erie Islands Conservancy reported on Facebook on September 9th, noting monarchs were taking refuge in several island preserves. “Large concentrations of monarchs were found in large trees out of the wind” near Lake Erie on 9-8-18 and 9-9-18, including at Scheeff East Point Preserve and Massie Cliffside Preserve on South Bass Island in Lake Erie and at Middle Bass East Point Preserve on Middle Bass Island in Lake Erie. Video and images of the roosts were posted to their Facebook page on September 9th.

September 10, 2018, Monarchs cluster in dogwood at Ottawa National Wildlife Refuge (Photo by Candy)

September 10, 2018, Monarch cluster in willow at Ottawa National Wildlife Refuge (Photo by Candy)

Reports continued along Ohio’s shoreline. Nothing was more spectacular than the monarch fallout that occurred at Ottawa National Wildlife Refuge in Oak Harbor, Ohio, along the Lake Erie shoreline beginning on 9-8-18.

September 10, 2018, Monarch sips water from its body at Ottawa National Wildlife Refuge (photo by Candy)

Monarchs lined up on the leeward side at Ottawa National Wildlife Refuge (Photo by Jackie Riley)

Roost sizes increased as we neared Lake Erie (Ottawa National Wildlife Refuge) (Photo by Jackie Riley)

Small portion of one of over 70 roosts along a 6 mile trek (Ottawa National Wildlife Refuge) (Photo by Jackie Riley)

Struggling to gain a foothold in the winds (Ottawa National Wildlife Refuge) (Photo by Jackie Riley)

Holding steady on the nearest plant (Ottawa National Wildlife Refuge) (Photo by Jackie Riley)

Refuge staff reported conducting a monarch count from 7-9:30am on 9-9-18, during which they counted 30,000 monarchs roosting in trees along the roads on the park’s Wildlife Drive. Staff reported, “We are experiencing the remnants of Gordon, so we have strong wind pushing off of Lake Erie (16-20mph) creating a Nor’easter. The water levels are pretty high from a combination of rainfall and lake levels over the past 20 hours. Temps are about 60 degrees F with high humidity. The monarchs are roosting on the western side of the trees out of the wind as much as they can be, but they are still bouncing around like crazy. There are pockets of them low in willows and dogwood, but even more towards the tops of cottonwood and maple trees. They were packed in there so tightly that in spots we thought that the leaves had started to change until we had a closer look! There are also monarchs moving over the marshes in the hundreds…Every tree had monarchs on it, from South Estuary Avenue thru North Estuary Avenue and parts of Veler Road and Trumpeter Trail, and a small section of Stange Road. Absolutely incredible.”

Massive roost with many in motion at Ottawa National Wildlife Refuge (Photo by Jackie Riley)

Jackie W. Riley of the Ohio Lepidopterists Society also reported from Ottawa National Wildlife Refuge later that same day (9-9-18). Riley reported viewing monarchs from 2-4:15 pm at the refuge, and at first estimated seeing approximately 2 million monarchs. She later revised her estimate to 200,000 after counting monarchs from over 400 photos she had taken during that 2 hours. Her photos were instrumental in documenting the magnitude of the event. This was truly a remarkable fallout of monarchs, nothing close to this has been seen since 96,000 monarchs were recorded at Point Pelee on September 6, 1993, including two overnight roosts of 7,500 and 3,000 individuals (cited in Wormington, A. 1994. A mass migration of Monarchs at Point Pelee, Ontario. pp. 26-27. In Hanks, A. J. (ed.), Butterflies of Ontario and summaries of Lepidoptera encountered in Ontario in 1993. Toronto Entomologists Association Occasional Publications 27-95.)

Monarchs roosting in Ottawa National Wildlife Refuge (Photo by Douglas Brockway)

Riley reported, “There were many independent roosts, but outstanding were the wooded stretches along the dike roads that held mega roosts with strands of smaller roosts that continued for many yards. Six different dike roads were involved. I was at the refuge the day before (Saturday 9/8/19), and saw NO roosts. However, there were reports of some smaller ones. So, in 24 hours, the roosts went from some, (I think it read a count of 1,000 individuals or more) to the exponential numbers that I saw.”

Riley further stated, “I would guess there were 50 roosts (several dozen). I stopped counting the roosts after the first 12 and figured I was less than one-third the way through the refuge auto-tour. The bulk of the roosts were further north which was the last two-thirds of the tour. Roosts were spread out and thin for the first one-fourth to one-third of the tour…The massive roosts were at one point 100 feet off the lakeshore that had pounding waves and 35mph+ sustained winds. All the monarchs were on the leeward side of the woods that sat between the road and the shoreline. A perfect scenario for them to find shelter immediately coming in off the lake. Weather notes for 9/9/2018: 2 pm-4:15 pm is when I saw them. 63F, 100% sky cover, raining at 4:15pm. Winds over the lake were at least NE 35mph sustained. Winds inside the refuge ranged from NE 10-25 mph depending on location. I believe the overnight temps were in the mid-high 50Fs with rain in the a.m. through 12pm.” Riley noted there were fields of sunflowers and a small amount of goldenrod available for nectaring along the Wildlife Drive.

Notably, Patrick Hogan of Tomahawk Archers and Douglas Brockway of Ottawa National Wildlife Refuge (ONWR) both separately found a tagged monarch at ONWR during the weekend storm. The monarch was tagged with the code YUJ012 and was originally tagged 4 days earlier in Waterford, PA on 9-5-18. This monarch’s likely southwest trajectory along Lake Erie’s southern shoreline, unexpectedly moving west to northwest in the last leg of its flightpath, was likely due to the strong NNE winds moving through the region as Tropical Storm Gordon remnants moved through the area. Doug stated, “I have been coming to ONWR for over 60 years, and never before in my lifetime have I seen this many monarchs.”

By September 10th, the Nor’easter was moving out of the Lake Erie region. The sun emerged and it quickly began to warm up. I had been unable to visit Ottawa National Wildlife Refuge on 9-9-18, but I rushed to the refuge early in the morning on the 10th. It was still rainy and a little cool when I arrived, and the rangers kindly arranged to shuttle visitors out to the monarchs. It continued to warm up as we waited for the shuttle, with light winds around 8-10 mph at times. We left at 10:30am, and air temperatures were 58-62F at that time. Clearly, these temperatures were above flight threshold. As a result, most of the monarchs were gone by the time we reached the roosting sites, with only around 1000 monarchs left, scattered along South Estuary drive. I captured a few dozen photos and it was wonderful enjoying the company of fellow monarch enthusiasts, despite the near constant drizzle. I figured the monarchs would head for fields with large numbers of wildflowers to feed (nectar source). I later found some monarchs in the meadows surrounding the nature center, and a small roost was forming in the line of cottonwood trees across from the barn. But it was clear—the improving weather meant the monarchs would now resume their journey south. Subsequent posts on Journey North and social media indicated the roosts were breaking up throughout the region, and our adventure was over.

The weekend’s historic monarch migratory event was truly a once-in-a-lifetime experience, resulting in cherished memories for years to come. Remarkable. Unforgettable. Historic.

Monarchs roosting in Ottawa National Wildlife Refuge (Photo by Douglas Brockway)

One of the largest roosts observed at the Ottawa National Wildlife Refuge (Photo by Jackie Riley)

Additional photos:
flickr.com/photos/candy__kasey/albums/72157700912789324

Monarch Watch Update August 2019

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Greetings once again Monarch Watchers!

This year marks Monarch Watch’s 28th season – wow!

The number of communications we receive can be overwhelming at times (especially this time of year) so we ask for your patience – we are not always able to respond in a timely manner but we do try to address every email, voicemail and letter we receive. We love to hear from you but please be sure to check out all of the information we have online via our Website, Blog, Facebook page, etc. before contacting us with questions. THANK YOU! 🙂

We have a TON of information to share this time around so let’s get right to it. This update includes:

1. Monarch Population Status
2. Western Monarch Population Status
3. Submitting Tag Data for the 2018 Season
4. Monarch Watch Tagging Kits: New tag for 2019!
5. Tagging Wild and Reared Monarchs
6. Chip in for Monarch Watch in 2019!
7. Grant-Sponsored Free Milkweed Programs
8. Monarch Waystations
9. Collect Milkweed Seed for Monarch Watch
10. Monarch Calendar Project
11. Upcoming Monarch Watch Events

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1. Monarch Population Status —by Chip Taylor
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Right now, in most of the breeding area, the prospects for a normal summer and a reasonably robust population look quite good. The exception is the northeast (east of Toronto in Canada, and most of eastern New York, Pennsylvania and north through New England). The colonization of those areas by first generation monarchs was scanty with low temperatures for the first half of June. Further, a colder than normal summer is predicted for most of that region which will retard population development. The migration in the east this fall will be on the low side relative to good years.

As you may already know from previous communications, I partition the annual cycle into 6 stages in an effort to understand the interannual variation in monarch numbers. This stage–specific model breaks down as follows: 1) overwintering (late Oct–early April); 2) return migration through Mexico (late Feb–April); 3) breeding in the US in March and April; 4) recolonization of the regions north of 37N (May–early June); 5) summer breeding north of 37N (June–August); and 6) fall migration (August–Oct). While there is some overlap, each stage is intended to capture the dominant activity during that period.

After Stage 4, I said the overwintering population was likely to be between 4–5 hectares and trending toward 4. Stage 5 recolonization has been excellent with respect to both timing and numbers, with the exception of the northeast. Based on the recolonization data and the long–term temperature forecasts for the Upper Midwest and the north central region, my prediction is that the 2019–2020 overwintering population will be at least 5 hectares and could trend toward 6 hectares if the summer temperatures from 80W (western Pennsylvania) to the west (105W) average at least a degree above the long–term averages. I will summarize the outcome of Stage 5 (June–August) in early September.

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2. Western Monarch Population Status
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Thank you to David James and Gail Morris for providing the following reports.

PACIFIC NORTHWEST
After the lowest overwintering population in California ever recorded, the western monarch population is struggling to bounce back. Numbers of breeding monarchs seen during spring and early summer in California, Oregon, Washington and Idaho have been very low. For example, only 4 confirmed sightings have been made of monarchs in Washington. None have been reported from British Columbia. Normally by now dozens of monarch sightings in Washington and British Columbia would have been reported.

It appears the northward migration from California was sparse and basically petered out by the time it reached the Oregon/Washington state border. The only ‘hotspot’ of monarchs in the Pacific Northwest is in southern Oregon. An estimated 20-30 monarchs have been sighted in this region during the past month or so and we are expecting reasonable numbers there by late August. One citizen scientist reported that a single female that visited her milkweed habitat in Brookings, Oregon laid almost 600 eggs on her milkweed over a period of a few weeks! In contrast, Idaho like Washington has seen just a handful of confirmed monarch sightings so far this season. Monarch status in California is less certain with few reports in central and northern California but an apparent abundance in southern California.

There is still time for a significant population build-up particularly in California and southern Oregon. However, the overwintering population this year is likely to be similarly poor to last year. —Dr. David James, Washington State University

SOUTHWEST
In spring we were worried – would we see any monarchs at all after the dismal overwintering counts in California? Then monarchs began to appear in southern New Mexico and Arizona near the Mexican border and continued to move northward through the region.

The Southwest states all experienced lower than normal temperatures in late winter and spring this year, slowing the spring migration through the region. Both Arizona and New Mexico reported higher than normal spring sightings in the low to mid elevations and many of these appeared to be remigrants from Mexico. Monarchs spending the winter in the lower deserts of California and Arizona were late to leave the areas as well. In fact, Tucson, Arizona was still reporting monarchs in early July despite temperatures above 100 degrees. Monarchs usually appear in the higher elevations above 6,500 to 7,000 feet by early July but none have been reported. A late season snowstorm near Memorial Day may have left its mark on the monarch population, but we are hopeful some will still appear.

Nevada reported monarchs in the Las Vegas area in late March and early April. The first sighting was reported in late April in the Reno area. Monarchs seem to be present in pockets with some areas reporting several and others mainly reporting their absence. In contrast, Utah has more monarch sightings than last year, especially in the Salt Lake City area. There is still more time for the population everywhere to recover before the Fall migration and we are all hopeful.

We are hoping for a low to modest fall migration but there will be monarchs in the area to observe and hopefully tag. —Gail Morris, Southwest Monarch Study

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3. Submitting Tag Data for the 2018 Season
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Thousands of you have already submitted your 2018 season tag data to us by mail or via our online submission form – thank you! We are still receiving datasheets and if you haven’t submitted your data yet 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 Tagging Data Here” 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. Monarch Watch Tagging Kits: New tag for 2019!
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If you have tagged monarchs before, you’ll notice that this year’s tags look a little different. We’ve reduced the amount of text on the tag and added a letter to the codes so be sure to record the complete alphanumeric code (four (4) letters followed by three (3) numbers; e.g. AXYZ123). See the new tag layout and all of the 2019 materials by visiting the 2019 Monarch Tagging Program page at https://monarchwatch.org/tagging

Monarch tagging is an important tool to help us understand the overall dynamics of the monarch population. Tags for the 2019 fall tagging season are available and we have started shipping them out, ahead of the migration in your area. If you would like to tag monarchs this year, please order your tags soon as they are going fast! Tagging Kits should arrive within 7-10 days but priority will be given to preorders and areas that will experience 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 2019 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.

2019 datasheets and instructions are also available online 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 at https://monarchwatch.org/tagging

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5. Tagging Wild and Reared Monarchs
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The following is an abbreviated version of our “Tagging wild and reared monarchs: Best practices” article recently posted to our Blog. The complete text of the article is available via https://monarchwatch.org/blog

Over the years, thousands of taggers have contributed to our tagging database. It is an enormous record and a veritable gold mine of information about how the migration functions. The record represents at least 1.8 million tagged butterflies and lists where, when and by whom each butterfly was tagged. The sex of each butterfly and whether the butterfly was wild–caught or reared, tagged and released is also recorded. These data have told us a lot about the migration. Yet, this record could be improved but we need your help. Diving into the data has revealed a number of surprises such as the difference between the probability that a reared monarch will reach Mexico and the probability that a wild–tagged monarch will do so. The recovery rate is higher for wild–caught monarchs (0.9% vs 0.5%) and it is the data from the wild–caught butterflies that tell us the most about the migration. Frankly, for some analyses, we have to set the reared monarch data aside. That doesn’t mean it is not valuable, but its uses are limited.

It should be noted that for tagging data purposes, monarchs captured as adult butterflies should be reported as WILD and adult monarchs reared from the egg, larva, or pupa stage should be considered REARED.

TAGGING WILD-CAUGHT MONARCHS
For wild-caught monarchs we need to:
1. increase the number of taggers from western Minnesota and Iowa westward into Nebraska and the Dakotas to give us a more complete understanding of dynamics of the migration;

2. increase the number of wild monarchs that are tagged since these provide the most valuable data; and

3. increase the number of taggers who tag from the beginning of the tagging season in early August until the migration ends. Tagging records for the entire season will help us establish the proportion of the late–season monarchs that reach the overwintering sites. When tagging wild–caught monarchs, many taggers run out of tags well before the season ends. That’s great, but it would help us to know when all tags had been used by indicating this via the online tagging data submission form.

TAGGING REARED MONARCHS
Reared butterflies tend to average smaller than wild migrants. That difference can be reduced significantly if careful attention is given to rearing larvae under the best possible conditions. Large monarchs have the best chance of reaching Mexico, surviving the winter and reproducing in Texas. There are several reasons for this: better glide ratio, better lift with cross or quartering winds, larger fat bodies, more resistance to stress, etc. There are very few small monarchs among those that return in the spring. For those of you who prefer to rear, tag and release, we have a few suggestions:

1. Rear larvae under the most natural conditions possible.

2. Provide an abundance of living or fresh–picked and sanitized foliage to larvae.

3. Provide clean rearing conditions.

4. Plan the rearing so that the newly–emerged monarchs can be tagged early in the migratory season (10 days before to 10 days after the expected date of arrival of the leading edge of the migration in your area).

5. Tag the butterflies once the wings have hardened and release them the day after emergence if possible.

6. When it comes to tagging, tag only the largest and most–fit monarchs (see complete article for some guidelines). Records of tags applied to monarchs that have little chance of reaching Mexico add to the mass of tagging data, but do not help us learn which monarchs reach Mexico – unless the measurements, weight and condition of every monarch tagged and released is recorded. There are a few taggers who keep such detailed records and those data can be very informative. If you collect such data and are willing to share it please contact us; do not add this information to the standard tagging datasheet.

As a final note, this text is not a directive. We are not telling you what to do; rather, we are simply providing suggestions that may lead to more successful rearing and tagging efforts.

The expanded version of this article “Tagging wild and reared monarchs: Best practices” is available via https://monarchwatch.org/blog

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6. Chip in for Monarch Watch in 2019!
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Several years ago, we launched our first “Chip in for Monarch Watch” Fundraising Campaign in honor of our director and founder, Chip Taylor (who’s birthday happens to be at the end of this month, 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 the previous donor comments on the Chip in for Monarch Watch page – the connections that are facilitated by monarchs and Monarch Watch are truly extraordinary.

This year’s Chip in for Monarch Watch 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 fully tax-deductible donation of any amount during our 2019 “Chip in for Monarch Watch” fundraising campaign.

Visit https://monarchwatch.org/chip for more information or to submit your pledge and tax-deductible donation. Please be sure to leave your comments, thanks, birthday wishes, etc. for Chip via the Chip in for Monarch Watch Form at https://form.jotform.com/82141035824146

Thank you for your continued support!

Quick Links:

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

– Chip in for Monarch Watch Form (to leave comments, thanks, birthday wishes, etc.):
https://form.jotform.com/82141035824146

– Donate Now via the KU Endowment: http://kuendowment.org/monarch

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7. Grant–Sponsored Free Milkweed Programs
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For complete details about applying for our Free Milkweeds Grants please visit https://monarchwatch.org/free-milkweeds

We are still able to accept about 25 more free milkweeds for schools and nonprofits applications before the grant quota is met. It would be great to have applications from ecoregion 222 (see map at https://monarchwatch.org/milkweed/market).

We have fulfilled our latest grant for distributing 100,000 free milkweeds for restoration projects. This brings the total to over 500,000 free milkweeds since Fall 2015. We are awaiting approval of funding for Spring 2020 grants.

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8. 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 (mapped location will be approximate for privacy). 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 14 July 2019, there have been 25,131 Monarch Waystation habitats registered with Monarch Watch! Texas holds the #1 spot with 2,110 habitats and Illinois (1,948), Michigan (1,845), California (1,609), Ohio (1,276), Virginia (1,202), Pennsylvania (1,120), Florida (1,095), Wisconsin (1,065), and Missouri (797) 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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9. Collect Milkweed Seed for Monarch Watch
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Monarch Watch is seeking donations of milkweed seed collected from wild populations. Our greatest need is for A. incarnata (swamp) and A. tuberosa (butterfly) throughout their ranges; A. syriaca (common) from the northeast; A. viridis (green antelopehorn), A. oenotheroides (zizotes), and A. asperula (antelopehorn) from Texas; and A. speciosa (showy) from Kansas, Nebraska, and Colorado.

Please visit our seed collecting page for further instructions: https://monarchwatch.org/bring-back-the-monarchs/milkweed/seed-collecting

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10. Monarch Calendar Project
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If you are recording your monarch observations for this project and would like to submit your data for the spring (1st) period please do so using the appropriate form, based on your location:

For locations SOUTH of (less than) 35N latitude (March 15-April 30, 2019) please use this form: https://forms.gle/dcmxnJGNqqTUwdtKA

For locations NORTH of (greater than) 35N latitude (April1-June 20, 2019) please use this form: https://forms.gle/BU6aqipV49A2krgy5

As soon as the fall period ends for all locations (September 25) we will send out a link for submission of that data.

Monarch Watch continues to seek the assistance of hundreds of monarch enthusiasts (citizen scientists) in collecting observations of monarchs in their area during specific periods of the spring and fall. If you would like to participate, all you have to do is: 1. REGISTER (just so we know where you are located and how to reach you), 2. RECORD (keep a record of the number of monarch butterflies you observe each day during the time period dictated by your location) and 3. SUBMIT (at the end of the observation period in the fall we will send participants a link to an online form to submit their observation data).

Complete details and a link to the short registration form are available at

https://monarchwatch.org/calendar

Please note that the fall observation period for those of you in the Southern U.S. runs from August 1 – September 25 so you need to start recording your monarch observations now! For northern locations (greater than 35N latitude) the fall period runs from July 15 – August 20 so recording should be going on now, but it is not too late to join in!

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11. Upcoming Monarch Watch Events
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Monarch Watch Fall Open House (Free event)
Saturday, September 14, 2019
9am–2pm
Lawrence, Kansas

Join us at our Fall Open House at Foley Hall (KU’s West Campus) to celebrate the arrival of migrating monarchs coming from the north. This free event is designed to please children and adults alike. As usual, we will provide refreshments, lots of show & tell (including a honey bee observation hive, our tarantulas, and white monarchs), tours of our gardens and lab space, hands-on activities, games, videos, monarch tagging demonstrations, and, of course, lots of monarch caterpillars, chrysalises, and butterflies!

Details at https://monarchwatch.org/openhouse

Monarch Watch Tagging Event (Free event)
Saturday, September 21, 2019
8am–12pm
Lawrence, Kansas

This year’s tagging event will once again be held at the Baker Wetlands Discovery Center (1365 N. 1250 Rd. Lawrence, KS 66046).

This free, all-ages, public event is sponsored by Monarch Watch, Jayhawk Audubon Society and the Baker Wetlands Discovery Center. There is no charge to participants and no experience is necessary – we’ll provide tags, nets, instruction, and refreshments.

We’ll post lots of photos via Facebook so if you are not able to join us in person be sure to check them out later in the day.

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

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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 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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Tagging wild and reared monarchs: Best practices

Greetings taggers and welcome to the 2019 monarch tagging season. This year marks Monarch Watch’s 28th season! Over the years, thousands of taggers have contributed to our tagging database. It is an enormous record and a veritable gold mine of information about how the migration functions. The record represents at least 1.8 million tagged butterflies and lists where, when and by whom each butterfly was tagged. The sex of each butterfly and whether the butterfly was wild–caught or reared, tagged and released is also recorded. These data have told us a lot about the migration. Yet, this record could be improved but we need your help. Diving into the data has revealed a number of surprises such as the difference between the probability that a reared monarch will reach Mexico and the probability that a wild–tagged monarch will do so. The recovery rate is higher for wild caught monarchs (0.9% vs 0.5%) and it is the data from the wild–caught butterflies that tell us the most about the migration. Frankly, for some analyses, we have to set the reared monarch data aside. That doesn’t mean it is not valuable, but its uses are limited.

Given the difference between the recovery rates of wild–caught and reared monarchs, what are our goals going forward? For wild–caught monarchs, we have several goals. First, we need to increase the number of taggers from western Minnesota and Iowa westward into Nebraska and the Dakotas. This region is known to produce large numbers of monarchs and those tagged have high recovery rates. Increased tagging in this area will give us a more complete understanding of dynamics of the migration. Second, we need to increase the number of wild monarchs that are tagged since these provide the most valuable data. Third, we need to increase the number of taggers who tag from the beginning of the tagging season in early August until the migration ends. Tagging records for the entire season will help us establish the proportion of the late–season monarchs that reach the overwintering sites. When tagging wild–caught monarchs, many taggers run out of tags well before the season ends. That’s great, but it would help us to know when all tags had been used by indicating this via the online tagging data submission form.

For those of you who prefer to rear, tag and release, we have a few suggestions as to how you might improve the odds that your reared monarchs will reach the overwintering sites in Mexico. But, it is more than reaching Mexico. The best outcome for a wild monarch is to survive the migration, the winter conditions, the flight north in the spring and to successfully reproduce in Texas in the spring. It seems reasonable that this should be the goal for those who choose to rear, tag and release. To reach that goal, we have to know something about the wild monarchs that allows them to survive. The migration is a strong selective force. It eliminates the weak, those with diseases, the undersized and those with genetic and other deficiencies. It also eliminates those that have not received the environmental cues that properly trigger diapause and the orientation and directional flight characteristics of the migration. One way to increase the success rate for reared monarchs is to rear monarchs in a way that maximizes their exposure to environmental changes (day/night temperatures, changing photoperiod with the ability to sense sunup and sundown, etc.) that occur in the fall. In other words, rearing outdoors, on porches, in pole barns, open garages, etc., would likely produce better results than rearing in an air–conditioned kitchen, spare bedroom or similar space.

As to the actual rearing, raising the monarchs on living plants–potted or in the ground–is likely to produce the largest monarchs, provided that the monarch larvae have an abundance of foliage to feed on at all times. Cut foliage in the form of leaves also works well, but the leaves have to be fresh and abundant relative to the numbers of larvae in each container. Containers should be cleaned each day once the larvae reach the 4th instar. To avoid passing the monarch disease Ophryocystis elektroscirrha (O.e. or OE) from outdoor monarchs to reared monarchs, both the living and cut foliage can be sanitized using a 10% bleach solution with a drop or two of liquid soap added. After soaking in the bleach solution for two minutes, the leaves should be rinsed thoroughly with clean water and patted dry before being fed to larvae. Living plants can be sprayed with the bleach solution and then rinsed. If you are using cut stems with leaves intact, they can be cleaned the same way. In that case, be sure to cut the stems under warm water before placing them in vases, etc. The warm water keeps the latex vesicles from closing down the transport of water to the leaves. Cut stems work to feed larvae, but they can go limp and be less suitable as a food source than cut leaves.

We are offering these suggestions since reared butterflies tend to average smaller than wild migrants. That difference can be reduced significantly if careful attention is given to rearing larvae under the best possible conditions. Large monarchs have the best chance of reaching Mexico, surviving the winter and reproducing in Texas. There are several reasons for this: better glide ratio, better lift with cross or quartering winds, larger fat bodies, more resistance to stress, etc. There are very few small monarchs among those that return in the spring.

To summarize:
1. Rear larvae under the most natural conditions possible.

2. Provide an abundance of living or fresh–picked and sanitized foliage to larvae.

3. Provide clean rearing conditions.

4. Plan the rearing so that the newly–emerged monarchs can be tagged early in the migratory season (10 days before to 10 days after the expected date of arrival of the leading edge of the migration in your area*).

5. Tag the butterflies once the wings have hardened and release them the day after emergence if possible.

6. When it comes to tagging, tag only the largest** and most–fit monarchs. Records of tags applied to monarchs that have little chance of reaching Mexico add to the mass of tagging data, but do not help us learn which monarchs reach Mexico – unless the measurements, weight and condition of every monarch tagged and released is recorded. There are a few taggers who keep such detailed records and those data can be very informative. If you collect such data and are willing to share it please contact us; do not add this information to the standard tagging datasheet.

As a final note, this text is not a directive. We are not telling you what to do; rather, we are simply providing suggestions that may lead to more successful rearing and tagging efforts.

*Migrations seem to move in concert with the declining sun angle at solar noon (SASN). The fastest migrations have a leading edge of 57 degrees. Therefore, “early” is defined as 10 days either side of when the sun angle at solar noon reaches 57 at your latitude. To determine SASN for your latitude, visit suncalc.org. A table of SASN values by latitude and/or further information will be posted at a later date.

**The easiest way to judge the size of your monarchs is to measure the forewing from the base to the apex of the wing (Figure 1). These measures range from 46–52 mm with most migratory monarchs measuring 49–51 mm. After some experience with both wild and reared monarchs, it is relatively easy to judge those that are below 49 mm.

Figure 1. Measuring monarch forewing.

Monarch Population Status

Stage 4 (1 May–9 June) Update

As I indicated in the Status of the Population post to the Monarch Watch Blog on 2 May, I partition the annual cycle into 6 stages in an effort to understand the interannual variation in monarch numbers. This stage–specific model breaks down as follows: 1) overwintering (late Oct–early April); 2) return migration through Mexico (late Feb–April); 3) breeding in the US in March and April; 4) recolonization of the regions north of 37N (May–early June); 5) summer breeding north of 37N (June–August); and 6) fall migration (August–Oct). While there is some overlap, each stage is intended to capture the dominant activity during that period. For example, in Stage 3 (March–April) monarchs continue arriving from Mexico through most of March; later, in the second half of April, some first-generation monarchs are beginning to move north. Nevertheless, the most important action during that stage – the one that has the greatest impact on the population – is the reproductive success of the monarchs that returned to the South Region from Mexico.

In the earlier posting, I provided an estimate based on the conditions observed through Stage 3. Specifically, I said “my current prediction is that the overwintering population will be in the range of 4–5 hectares. At this writing, I see the population as trending toward 4 hectares.”

We are now at the end of Stage 4 (1 May–9 June). It is during this stage that the majority of first–generation monarchs originating from the South Region (primarily Texas and Oklahoma) migrate north to colonize the areas north of 37N (40N more precisely defines the southern limit of the northern breeding range in terms of numbers of monarchs generated that join the fall migration yet 37N is more inclusive). This stage ends on the 9th of June. The end date is somewhat arbitrary. We know that monarchs stop directional, hence migratory, flight sometime in early June but are not sure when. However, directional flight appears to stop before the 9th. We haven’t been able to detect directional flight after the 6th of June in Lawrence, KS. Data are needed on this feature of the annual cycle. Sightings recorded after this date are assumed to represent butterflies that had arrived in the area before the 10th. In fact, there is little evidence in the first sightings data reported to Journey North of an expansion of the northern distribution of monarchs after 9 June.

Recolonization is all about timing and numbers. In 2012, the monarchs arrived in the northern breeding areas too soon and in 2013 too late, and in both years the population declined. This observation tells us there is a “sweet spot” or optimal set of dates to arrive in the northern breeding areas. Our original assessment was that the optimal period was between 11–30 May. It now appears that this should be shortened to 16–30 May. The following is how the first sightings reported to Journey North break out this year vs 2018.

Table. First sightings north of 37N and east of 110W.

So, what can be said about these data? First, the number of first sightings for these two years are the highest in the Journey North first sightings records. These numbers probably reflect both excellent returns and a larger number of people willing to report first sightings. In 2018, the higher percentage of first sightings from 1–15 May combined with favorable temperatures for larval development immediately after arrival in the northern area may have aided population growth. The higher number of first sightings this year, especially in the north central region (Michigan, Indiana, Ohio, Ontario), is also a positive. Overall, both years are exceptional and quite similar, and since we know that the first sightings of 2018 were a precursor to an overwintering population of 6.05 hectares, the highest number recorded since 2006, what do the 2019 numbers tell us about the overwintering numbers in 2019–2020? Should we expect another population of 6 hectares? Maybe, but it’s too early to say. We still have to see how Stage 5 works out. Right now, in most of the breeding area, the prospects for a normal summer and a reasonably robust population look quite good. The exception is the northeast (east of Toronto in Canada, and most of eastern New York, Pennsylvania and north through New England. The colonization of those areas by first generation monarchs was scanty with low temperatures for the first half of June. Further, a colder than normal summer is predicted for most of that region which will retard population development. The migration in the east this fall will be on the low side relative to good years.

After Stage 4, I said the overwintering population was likely to be between 4–5 hectares and trending toward 4. Stage 5 recolonization has been excellent with respect to both timing and numbers, with the exception of the northeast. Based on the recolonization data and the long–term temperature forecasts for the Upper Midwest and the north central region, my prediction is that the 2019–2020 overwintering population will be at least 5 hectares and could trend toward 6 hectares if the summer temperatures from 80W (western Pennsylvania) to the west (105W) average at least a degree above the long–term averages.

I’ll update this prediction, if necessary, for the premigration newsletter and will summarize the outcome of Stage 5 (June–August) in early September.

I wish to thank Janis Lentz for her assistance in summarizing data for this article.

Monarch Population Status

Stage 3 (March–April) Update

As most of you know, I endeavor to predict how the monarch population is developing each year. While I always fail to correctly predict the exact number of hectares measured at the overwintering sites, I’m getting better at it with each iteration. Last year it was evident as early as March that the population was going to increase substantially from the relatively low numbers measured in 2017 (2.48 hectares). After watching the population develop through March and April by tracking both first sightings reported to Journey North and then following the colonization of the northern breeding areas (>37N) in May and early June, it was even clearer that the migratory and overwintering population was going to be much larger than recorded in 2017. I then followed the conditions during the summer months, and again, all signs were positive and it was clear that the overwintering hectares would be at least as great as those of 2008 (5.06 hectares) and perhaps larger. My final prediction was that the overwinter population was going to be greater than 5 hectares, but I couldn’t say how much greater. I predicted the direction of change correctly and was close on the magnitude of change but missed the mark. The actual total was 6.05 hectares. Which brings me to why this is the Stage 3 Update.

In March I conducted a webinar of monarch population development through the sponsorship of the Monarch Joint Venture and the cooperation and facilities of the US Fish and Wildlife Service. In that webinar I introduced the idea of developing a Stage Specific Model for Monarch Population Development. This verbal model is based on my attempts to understand the interannual variation in monarch numbers. The data used to derive these predictions are based on the conditions associated with the growth of the monarch populations each year from 1996 to the present. These data include patterns associated with first sightings, rates and times of colonization and physical conditions, mostly temperatures, from March through October. There is a narrative for each year. Comparing and contrasting the responses of the population from year to year and particularly for years with extreme conditions has shaped this approach.

To understand the monarch annual cycle, I break down the year into 6 stages: 1) overwintering (late Oct–early April; 2) return migration through Mexico (late Feb–April); 3) breeding in the US in March and April; 4) recolonization of the regions north of 37N (May–early June); 5) summer breeding north of 37N (June–August) and 6) fall migration (August–Oct). Although overwintering mortality varies from year to year, the available mortality data for this stage are too fragmentary to be used in the model. Similarly, there are no estimates of the mortality experienced by monarchs from the time they leave the colonies to when they reach the milkweed rich areas of Texas. Mortality during this 600-800mile journey could be significant due to spring droughts, high temperatures and strong winds. Lacking these measures, we are left with first sightings in the US, mostly in Texas and Oklahoma, as a surrogate for both the relative survival and fitness of the overwintering population and the return migration. While first sightings have a number of limitations, the number of sightings as well as the temporal and spatial distribution of these sightings when examined in the context of the physical conditions and comparisons across years can be quite useful. I will deal with first sightings and my methods in greater depth at a later date. In the meantime, if interested, you might check out the webinar to see some useful year to year comparisons:

https://fws.rev.vbrick.com/sharevideo/3a32c09e-7d3d-45c7-9fa0-09d6913e6474

Getting back to Stage 3, it’s the critical period that sets the stage for what could happen through the rest of the season. Briefly, the key factors in Stage 3 are 1) the returning number of monarchs 2) their condition upon arrival, i.e. their structural and physiological conditions 3) the spatial and temporal distribution of the new arrivals through March and April 4) the temperatures that determine #3 and 5) the number of and spatial and temporal distribution of eggs as determined by 1-4. The distribution and abundance of fire ants could also be a factor, but there doesn’t seem to be any way to assess this threat though it is known that fire ant numbers decrease under drought conditions and increase when precipitation favors plant and insect growth.

Now that Stage 3 is at an end, we can compare the conditions during this past March and April with those of last year and previous years to get a rough approximation as to what to expect during the fall migration and next winter in Mexico. First, I can say unequivocally that the fall migration will not be as robust as last year and that the overwintering number of hectares will be less than 6.05 hectares. The conditions for Stages 3, 4 and 5 last year were all favorable for population growth. In Stage 3, the mean temperatures for March in Texas were 5.4 F above normal, yet due to cold temperatures that hovered over Oklahoma and north Texas the majority of returning monarchs were effectively confined to Texas through March and early April. These conditions have two outcomes, 1) most of the eggs laid by the returning monarchs were laid in Texas and 2) due to the higher temperatures, the larvae and pupae developed rapidly thus exposing the developing matures to lower rates of predation and parasitism. Another consequence of these conditions was a low mean age to first reproduction (egg to egg interval) for the first generation. A key factor in population growth is age to first reproduction with the fastest growing populations having the shortest age to first reproduction. The higher mean temperatures during Stage 4 (May and early June) facilitated recolonization of the summer monarch breeding areas north of 37N. As the first-generation monarchs arrived in the northern areas in the first part of June, the temperatures were again favorable for both flight and egg laying – more so than in most years. The good starting numbers and conditions in the northern breeding areas resulting from the conditions in Stages 3 and 4 were followed by warmer than normal summer temperatures in the Upper Midwest. Although 2F higher than normal, these temperatures were not in the range that results in drought conditions and lower life expectancy of adults and therefore a reduction in realized fecundity. The bottom line on 2018 is that the conditions in Stages 3-5 were the best since 2001 and may actually have been better than recorded for 2001.

So, what can we expect this coming fall and winter? Based on first sightings, temperatures, probable egg distributions, generation length and early May conditions, my current prediction is that the overwintering population will be in the range of 4-5 hectares. At this writing, I see the population as trending toward 4 hectares. However, higher than average temperatures for May and June-August in the Upper Midwest could result in a population that is closer to 5 hectares.

The positive conditions in Stage 3 this year include the highest number of first sighting recorded in the central flyway since Journey North has been recording these data. That seems to tell us that the relatively large population of 2018–2019 wintered well, in spite of reports that the butterflies were abnormally active during the winter, and navigated from the colony sites back to Texas without experiencing high mortality. Temperatures in Texas were lower than in 2018 which had the effect of again confining most of the egg laying by returning monarchs to Texas but also increased exposure to predators and parasites and increased generation length. Overall, the first generation produced in Texas and southern Oklahoma could be larger than in 2018 due to the larger number of returning monarchs. While that could be true, the predators and parasites could be more abundant this year. Unfortunately, we have no measures of the year to year variation in egg and larval mortality resulting from these causes. Due to the lower temperatures, the average date of departure from Texas and Oklahoma for first generation monarchs should be a bit later this year. That may not be a bad thing since the forecasts indicate that conditions for recolonizing the northern breeding areas won’t be favorable until the second half of May.

The bottom line for Stage 3 this year is that we can expect monarchs to have another good year, not as good as 2018, but a good year – assuming near average temperatures of Stages 4 (May–early June) and 5 (summer).