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).

Monarch Population Status

Will the population increase again this year? Last season the population increased from 2.48 hectares to 6.05 (see the January 30th Monarch Population Status announcement). If the monarchs wintered well, that is with a normal rate of mortality and morbidity, that should result in a relatively large (compared to recent years) returning population with the potential to yield another large migration and overwintering population. Right? Maybe and maybe not.

To forecast what might happen we have to know what happens during March and April in the South Region and then what happens in May as the first generation moves northward. Timing and numbers are critical to understanding the prospects that the population will grow or decline.

Ok, so what is happening now? There is good news, some questions and perhaps more good news.

The first bit of good news is the sighting of 27 monarchs in Texas in the first 10 days of March. That’s the highest number for this period since Journey North started keeping records in 2000. Some of these records indicate that monarchs are well into Texas, having reached Austin and beyond. The question is how many monarchs are already in Texas and how many are still moving northward through Mexico? It is probable that most of the monarchs are still en route and we know that substantial numbers still remain at some of the colonies.

I raise this issue because it looks like the two monarch pathways through Mexico (see figure below) are going to be shut down by cold weather from 15-22 March. This shutdown could mean that once the weather warms in northeast Mexico, monarchs could flood into Texas after the 22nd. The effect would be late arrivals for the majority of monarchs coming out of Mexico and that would not be a good thing. The peak arrival in Texas is usually from 21-25 March and often from 26-30 March. Later arrivals are often associated with lower population numbers.

The good news comes in twos. First, the weather for monarchs that have already reached Texas will be favorable for feeding, mating, egg laying, larval growth rate and movement to the northeast. Secondly, the long range forecast, if accurate, indicates that most of the returning monarchs will lay the majority of their eggs in Texas, and the southern half of Oklahoma. Restricting egg production to Texas and Oklahoma is a good thing since it will minimize the average age to first reproduction of the progeny of the returning monarchs. The population has increased each year egg distribution has been limited to the lower portion of the South Region.

Returning monarchs that have survived to mid-April in Oklahoma will be able to continue moving northeast once the daytime highs reach the lower 70s. A few of these may reach Kansas but the number reaching northeast Kansas, where I am, will be few, if any, unless the forecast is wrong and the numbers returning to Texas are higher than in recent years.

The bottom line — I’m cautiously optimistic that the population will get off to a good start this breeding season. I’m keeping my fingers crossed that my key assumptions – good returning numbers, restricted egg laying, and favorable weather conditions – will be validated in time.

The figure below represents the two main pathways by which returning monarchs enter Texas from Mexico. The distance along the coastal pathway to the milkweed-rich areas of Texas is about 600 miles. The montane or interior pathway is about 800 miles. The latter appears to be the favored route since the temperatures along the coastal pathway are often too high for migratory flight. The location markers represent all spring first sightings reported to Journey North for Mexico. Figure created by Janis Lentz.

Addendum
The flow of overwintered monarchs returning to Texas continued after the 10th and through the 14th 75 first sightings had been reported to Journey North. However, since Journey North hasn’t picked up the sightings posted to our email discussion list (Dplex-L) and perhaps some posted to Facebook, this number is an underestimate. Further, there have been at least four reports of sightings of 20 or more monarchs seen moving N/NE at different locations. These sightings of multiple monarchs on the move in short time periods are unprecedented. A review of the Journey North first sightings from 2000 to present shows that there was only one other year, 2012, with a similar number of sightings through the 14th – 87. As you may recall, March of 2012 was hottest ever recorded in the U.S. The population declined that year from 2.89 to 1.19 hectares. Now, as in 2012, substantial numbers of monarchs have advanced into areas ahead of the appearance of milkweeds. The Journey North Map of first sightings for 2012 indicates that the returning migrants moved too far north too soon, a factor that probably contributed to the lower numbers the following winter. That scenario seems unlikely to develop this year. According to the long-range forecasts, the temperatures are likely to limit most of the northern movement in the Midwest to Texas and Oklahoma. I’ve said it before “Every year is different yet every year is the same”. The trick is to distinguish what is the same through the multi-decade record from what is different each year and among years. – CT

Monarch Population Status

World Wildlife Fund Mexico in collaboration with CONANP and the Monarch Butterfly Biosphere Reserve (MBBR) announced the total forest area occupied by overwintering monarch colonies today. Fourteen (14) colonies were located this winter season with a total area of 6.05 hectares, a 144% increase from the previous season:

Figure 1. Total Area Occupied by Monarch Colonies at Overwintering Sites in Mexico

We will provide additional details as we receive and process them.

WWF release (in spanish): Aumenta 144% la presencia de la mariposa Monarca en los bosques mexicanos de hibernación

Monarch Population Status

It’s been more than a few years since we have seen a monarch migration as promising as the one that is taking place at this time (early September). The first fall roosts were reported to Journey North on the 11 August in Sauk Centre, Minnesota (45.7 N) and reports of additional roosts soon followed. There were multiple reports from Sauk Centre with the highest numbers reported on 30 and 31 August. Most of the roosts have been reported in the western portion of the Upper Midwest (eastern Dakotas to central Minnesota), but a number of others have been reported in eastern Ontario, Michigan, New York, and Ohio. Data for all the roost reports to Journey North can be found at: Journey North Monarch Roost Report 2018. A screen shot of the location of the roosts through 3 September is shown in Figure 1. To follow the roosts and therefore the migration visit Journey North Monarch Roost Map 2018. While the numbers of reported roosts through 2 September is encouraging, and is a signal of a robust migration, the estimated numbers of monarchs are also higher than seen in several years with 17 different roosts estimated to contain 1000 or more monarchs.

Figure 1. Distribution of overnight monarchs roosts reported to Journey North through 2 September 2018.

Tagging 2018

Interest in tagging has grown. Last year, a year with a moderate population (2.48 hectares) one that I was actually expecting to be larger, we issued over 320,000 tags. That was largest number of tags issued in one year to date. The returned data sheets have not all been tallied, but we are closing in on the final numbers and it appears that over 140,000 butterflies were tagged last season. That may well have been the highest proportion of tags applied of those issued since we started tagging in 1992. The highest number of tags applied in the past was estimated to be >106,000 in 2001. Requests for tags are off the charts again this year and due to the high demand we ordered extra tags. Unfortunately, they will all be spoken for by the time you read this. In fact, data sheets in both digital and paper form are being received at this time from those who tagged in the most northerly locations. Domestic recoveries, that is those within the US or Canada, are also being reported. Most, perhaps 90%, of these recoveries are of butterflies tagged within a mile or two of where they were observed. These reports tell us little about the migration. As a consequence, we assign less attention to these recoveries than those from Mexico, but there are some gems among these domestic recoveries and we will get to these in time. Please understand it takes us months to record all the records involved with the tagging program with our relatively small staff and the help of volunteers.

Overwintering numbers and fall conditions

In previous posts I’ve pointed out that the sequence of events and temperatures that determine how the monarch population grows through the season has been better this year than for any year since 2001. Based on this I’ve been projecting an overwintering population of 5 hectares, perhaps a bit more depending on the level of monarch production in the western portion of the Upper Midwest (longitudes 95W – 100W). Reporting from states in that region is typically minimal, but we recently received reports of substantial numbers of monarchs from western Kansas and the central Dakotas suggesting a good migration is underway through that area.

The last overwintering population of 5 hectares occurred in 2008 and this migration should reach that number, but there is still a big unknown. Will the fall conditions favor survival during the migration? We don’t really know how to answer this question. We can look to weather forecasts and nectar availability as inferred from drought indices, but we don’t really know how monarchs are affected negatively by weather events or nectar scarcity. While the long-range forecasts suggest average or slightly below average temperatures from the Upper Midwest through Texas, drought conditions in key areas could present problems for migrating monarchs, particularly in Texas, as shown in Figure 2. Most of the migration through Texas occurs in October so should sufficient rains occur, nectar scarcity would not be an issue. Monarchs still have to pass through northern Mexico, a traverse of another 600 miles or more depending on the routes taken. Unfortunately, there is no up to date information on the drought conditions in this region. The 31 July report from the North American Drought Monitor website suggested that the region was not abnormally dry, but that was before August, which is typically a dry month in that region.

Figure 2. Drought monitor showing increasing drought severity based on color gradients as of 28 August 2018.

A Message to all Taggers

Hear ye! Hear ye! Taggers take note! What you have contributed to monarch science over the years has been incredible! Collectively, you have tagged well over 1.5 million monarchs in the last 26 years, from the front range in Colorado to the Maritime Provinces in Canada. Further, you have tagged from the beginning of the migration in the vicinity of Winnipeg in early August until the last monarchs cross the border into Mexico in November. It is an amazing record that continues to provide new insights about the dynamics of the monarch migration. Congratulations and thank you.

We are often asked why we keep tagging. We know where monarchs come from that reach Mexico, right? The answer is yes, we do, but tagging and recovery of tagged monarchs is about more than origins. It’s about patterns that tell us what areas of the country contribute most to the overwintering numbers. It’s about the flow of the migrations, that is, how the migration progresses from its start in Canada to its end at the overwintering sites in Mexico. It’s about the influence of weather on migrations and the impact of habitat loss. It’s about the sex ratios and mortality during the migration and it’s even about events that happened 7-8 months before the migration. We are in the process of analyzing over 1.3 million tagging records and more than 13,000 recoveries and, I can tell you, the tagging results have things to say about all these points and more. The amount of monarch habitat is changing along with the climate and it turns out that tagging is one way of monitoring these changes. So please keep tagging from the start to the end of each migration. Your data are of great value.

Monarch Population Status

When it comes to estimating the size of the migration, each year is a series of experiments, with numerous hypotheses, during which I try to match what I know about monarchs with the progression of the seasonal conditions that influence both monarch behavior and plant growth. To make projections for each fall migration and overwintering population, I start with the numbers of monarchs measured at the overwintering sites in Mexico. Next, I focus on overwintering mortality, followed by the spring conditions as monarchs move northward from the overwintering sites to the milkweed areas in south and central Texas, and then the conditions in the South Region (TX, OK, LA, AR, KS) during the growth of the first generation in March and April. That is followed by attention to the conditions during the period from 1 May-9 June that allow, or don’t allow, first generation monarchs to reach the northern breeding grounds. Summer temperatures along with the seasonal distribution and amounts of rainfall are also in focus when estimating the fall and winter numbers. These stage and time specific assessments provide the context for a number of hypotheses or projections concerning the coming migration and the opportunities to tag monarchs each season. Sometimes I’m on the mark and sometimes I’m wrong. The point is to not only give those interested an idea of what to expect but to learn from my mistakes and few successes. Last year, I predicted a large population in the Northeast in general and for Cape May in particular. I was right on the money. However, I underestimated the impact of the drought that ranged from the eastern Dakotas through western Minnesota down through western Iowa. I also overestimated the production of monarchs in the rest of the Upper Midwest with the overall result that the overwintering population of 2.48 hectares was lower than the near 4 hectares I was expecting. These differences were reflected in the number of overnight roosts reported to Journey North through the migration and the relative success of taggers in the East and Midwest. Still, it was a great tagging season.

So, let’s see if I can do better this year. With respect to the Northeast, this should be another good season, although not as good as last year. In Canada, eastern Quebec will be down, but most of Ontario is on track to produce a substantial number of fall monarchs. The counts of monarchs per hour at Cape May will be lower this year, but will still be well above the long-term average. On the positive side, in the Upper Midwest, unless I’ve misjudged the situation once again, the migration should be the strongest since 2008 (a 5-hectare year) with the real possibility that the overwintering population could hit 5 hectares once again. Let’s see if I’m correct.

Dr. Lincoln Brower

An appreciation for Dr. Lincoln Brower who passed away on 17 July 2018 at his home in Virginia.

If you are familiar at all with monarch butterflies, you are certainly familiar with some of Linc’s many contributions to our knowledge of monarchs. Linc was a leader, often a singular voice on behalf of the monarch migration. It was through his advocacy and work with the Mexican government that the Monarch Butterfly Biosphere Reserve (MBBR) was established to protect the overwintering monarch population in Mexico. Linc was among the first to recognize that the weakest portion of the monarch’s annual cycle is the formation of the overwintering colonies within the oyamel forests on a few mountain tops in a relatively small region of central Mexico. He saw that protection of these sites was key to the preservation of the monarch migration and he worked tirelessly to safeguard these locations, sometimes earning the wrath of authorities and some colleagues. Yet, he was steadfast in his advocacy. To understand the relationship of the forest and the overwintering population, Linc, along with colleagues, undertook numerous studies to document everything from the microclimates of the forest to overwintering mortality due to predators and winter storms.

He was also a pioneer in the studies of plant/insect/predator interactions through his classic studies of the importance of cardenolides in milkweeds that provide protection to monarchs that consume the foliage as larvae. Through these studies he became a major contributor to the emerging field of ecological chemistry. The singular, and now iconic, picture of a young blue jay on the cover of Scientific American in 1969 had the effect of drawing attention to the complexities of plant/insect and predator relationships within and outside of mimicry complexes involving butterflies and other insects. This was the stuff of textbooks and courses in ecology and entomology. The diversity and quality of Linc’s many publications were recognized by numerous organizations that support conservation and by the scientific community as well. In 2007, on occasion of his 75th birthday, the Fifth International Conference on the Biology of Butterflies held a meeting in Rome at which Linc was honored for his scientific achievements. Two pictures from that event are provided below.

Lincoln Brower, Michael Boppre, Linda Fink, Toni Taylor, Chip Taylor, Steve Malcolm,
Myron “Meron” Zalucki, Dick Vane-Wright, Sonia Altizer, Karen Oberhauser

Lincoln Brower and I go back a long way. I first met Linc while working as Dr. Charles Remington’s assistant at Yale in 1960. Linc earned his PhD at Yale (1957) and frequently returned to visit with colleagues. Encounters with Linc were rare in the early years of my career. I worked on hybridization in sulphur butterflies for my PhD and through my early years at the University of Kansas. By 1973 it became clear that I was becoming increasingly, and dangerously, allergic to these butterflies forcing me to reinvent my self as a honeybee biologist studying Neotropical African honey bees (killer bees), an episode that lasted 22 years. As a person fascinated with butterflies, I followed Linc’s work on monarchs with interest throughout these early decades of my career. He may have known a bit about my work as well. Given changes in funding for honeybee research that were on the horizon, I decided to become involved with monarchs starting with a tagging program in 1992.

This brought me into contact with Linc once again. Though I thought I was well informed about monarchs, I was in fact quite naïve and I remember declaring to Linc that I thought there must certainly be other monarch overwintering sites. He was a bit bemused and gentle with me and with a bit more experience I soon abandoned the notion that the monarchs held secrets that Linc didn’t know. Because of my work with monarchs, Linc and I participated in a number of of the same meetings and have been members of organizations that have promoted monarch conservation. Through our interactions I found Linc to be the consummate protectionist, seeking always to maintain the status quo and resisting change. I’m more of a pragmatist in that I’m more willing to accept that there are processes in place that we can’t change but need to adjust to. He perhaps saw me as being too willing to accept change and I saw him as quite ridgid. These approaches clashed from time to time but, to both our credits, these relatively unimportant differences never became public. Nevertheless, as I pointed out to Linc in an email shortly before his death, though we saw things differently from time to time, we had always been on the same side in wanting the monarch migration to continue for generations to come.

Links to obituaries for Dr. Lincoln Brower and a blue jay/monarch story are found below.

Sweet Briar College:
http://sbc.edu/news/renowned-monarch-butterfly-expert-lincoln-brower-dies-but-his-legacy-lives-on/

New York Times:
https://www.nytimes.com/2018/07/24/obituaries/lincoln-brower-champion-of-the-monarch-butterfly-dies-at-86.html

Today:
https://www.today.com/news/life-well-lived-monarch-butterfly-scientist-dr-lincoln-brower-dies-t134589

LA Times:
http://www.latimes.com/local/obituaries/la-me-lincoln-brower-20180720-story.html

Monarch Joint Venture:
https://monarchjointventure.org/news-events/news/remembering-lincoln-brower-a-world-renowned-monarch-conservation-leader

Science Friday:
https://www.sciencefriday.com/articles/the-case-of-the-barfing-blue-jay/

Monarch Habitat Restoration in Oklahoma

Monarch Watch is continuing to partner with Tribal Environmental Action for Monarchs (TEAM) and Tribal Alliance for Pollinators (TAP) on habitat restoration efforts in Oklahoma. TEAM is a coalition of seven Native American tribal nations (Chickasaw, Seminole, Citizen Potawatomi, Muscogee Creek, Osage, Miami and Eastern Shawnee) that are taking part in a three year comprehensive training program learning all aspects of habitat restoration and native plant production. Each one of the TEAM partner tribes pledged to plant 5,000 milkweeds and 4,000 native nectar plants on their tribal lands as a part of the program. TAP is a new organization that was created to share the best practices and training protocols developed by TEAM to a larger audience of tribal nations who are seeking technical assistance in restoring habitat for monarchs and pollinators.

Jane Breckinridge, Euchee Butterfly Farm, Bixby, OK and Chip Taylor, Monarch Watch