Monarch Watch Update - September 2006



1) Status of the Population

2) Isotopes and the Natal Origins of Monarchs: Then and Now

3) Monarch Waystations

4) Monarch Monitoring at Cape May

5) Monarch Tagging Events

6) Communications – A Few Statistics

7) Degree Days for the 2006 Monarch Breeding Season

8) About Monarch Watch


Unless otherwise noted, all content was authored by Chip Taylor, edited by Jim Lovett, and Ann Ryan and published by Jim Lovett.


This Update is dedicated to the memory of Ryan Kanost, a promising young pre-med student and a dedicated member of the Monarch Watch critter crew during the 2005-2006 academic year. Ryan was killed by a hit and run driver as he crossed a street in Lawrence on the 23rd of September. We are saddened by the loss of this fine young man. - Chip

1) Status of the Population

This has certainly been an interesting year for monarchs. The overwintering population in Mexico for the winter of 2005-2006, though a modest 5.92 hectares, survived the winter well and there were no reported episodes of mortality due to storms or other calamities. As the winter’s survivors moved north in the spring, they evidently encountered conditions that allowed them to reproduce at an exceedingly high rate. The result of this reproduction was the largest wave of first generation monarchs to move north in the history of Monarch Watch (14 years) and in the memories of many long-term monarch observers. The arrival of large numbers of first generation monarchs and the large numbers of second generation larvae reported from most areas north of 42N gave rise to numerous enthusiastic reports and high expectations for one of the best migrations in a decade or more. Some of these expectations were met and others were not. Observers in the east, along the coast from Maine to New Jersey, but especially those in Massachusetts, Rhode Island as well as Long Island, reported extraordinary numbers of monarchs. I received at least 8 “once in a lifetime” reports from members of the public who witnessed thousands of butterflies either clustered on trees, feeding on seaside goldenrods or in flight. In Massachusetts, a number of long time butterfly observers declared that this was the largest monarch migration in 30-40 years. Further, at Cape May, Dick Walton, in collaboration with Lincoln Brower and others, recorded the second highest number of monarchs in the 15 year history of that program. Being the second highest is a bit misleading since, as I will explain below, the highest numbers recorded at Cape May are related to Hurricane Floyd.

While there is no doubt that the monarch population in the east was robust, the population in the Midwest, from Wisconsin to the eastern Dakotas, was disappointing and ranks as one of the lowest populations of migrants we’ve seen from that region since we began the tagging program in 1992 (the poorest year being 2004). The crash of the monarchs in the upper Midwest appears to have been due to high temperatures in July and early August and an extensive drought as I outlined in last month’s Update. The contrast between the monarch populations in the east this year, with its generally favorable conditions throughout the summer, and the Midwest, with extreme drought and high temperatures, once again demonstrates how monarch population size is largely a function of the weather.

Size of the Fall/Winter Population

In the August Update, based on the information available at that time, I estimated that the overwintering population this year would be close to 5.5 hectares. My pessimism was due to the low numbers of monarchs that seemed to be originating from the upper Midwest, an area that normally contributes substantial numbers of monarchs to the fall migration. Throughout late August and September reports from the upper Midwest consistently indicated a low population. Further, for the first time, many of the taggers in this region returned large numbers of unused tags. Although the population in the east was already known to be quite large, I did not feel that the numbers of monarchs from the east alone would be sufficient to populate Mexico with the average number of hectares of monarchs. So, I was conservative but made one provision, namely that I would raise the estimate to 6.5 hectares if the drought conditions in Texas improved enough to generate sufficient flowers for the migrating monarchs. There is still a significant drought in Texas (see Figure 1 below), but conditions did improve enough to allow the monarchs to pass through the state without high losses due to lack of water and nectar. We will have to wait until February, after all the colonies have been measured, to see if this prediction is accurate. For my record in predicting overwintering populations – some hits, some misses – see the Update for August 2006.

Figure 1. Drought monitor for 26 September 2006. Note extreme drought through central Texas.


2) Isotopes and the Natal Origins of Monarchs: Then and Now

Several years ago we participated in an isotope study of monarchs: and

I won’t go into the details of how this study was conducted here since this information is provided in the two links cited above but I do wish to point to one of the results, e.g. Figure 2. This figure is widely cited as it is the only data that pertains to the origins of the butterflies that reach the overwintering sites in Mexico. The figure clearly shows, as we have often repeated, that the majority of monarchs originate in the corn belt. The basis for this figure was the isotopic profiles obtained from dead monarchs collected at each of the overwintering sites after the summer of 1996. That was an extraordinary year for monarchs and the measures of the colonies revealed the largest monarch population, 21 hectares, since systematic attempts began in 1993 to measure the areas occupied by all monarch colonies. But the isotope study of 1996 was before Bt corn and Roundup Ready soybeans changed the landscape for milkweeds and before it became evident that seasonal conditions such as those seen in 2006 (and perhaps 2003) shifted the center of the distribution of the fall population from the Midwest to the East. Although the research on Bt corn was unable to show that corn pollen from Bt corn varieties that landed on milkweeds had a measurable impact on monarch survival, it is probable that the rapid adoption of Roundup Ready soybeans (genetically engineered Roundup/glyphosate tolerant varieties) has sharply reduced the availability of milkweeds in row crops, thus concentrating more of the egg laying on those milkweeds growing along roadsides, in pastures and other landscapes. Soybeans are used in rotation with corn and in our justification for the Monarch Waystation program I point out it is probable that 80 million acres of monarch habitat has been lost since these genetically modified strains were widely adopted in the late 1990s. (First approved in 1995, 1.2 million acres of Roundup Ready soybeans were planted in 1996 and 70-71 million acres in 2006). The loss of milkweed in row crops is important for two reasons, 1) corn and soybeans constitute 30% of the total summer breeding area for monarchs, and 2) a comparison of the productivity of various monarch habitats at the time of the Bt corn studies showed that more monarchs were produced per acre in row crops than in any of the other habitats. So, if we repeated the isotope study, this year or in the future, what would it show? Even if the weather conditions produced populations with similar distributions to those in 1996 in a future summer, it seems likely that the 50% area would expand because of the reduced availability of milkweed in the corn belt and would certainly move northward. Also, were the sampling done this winter, it seems probable that the 50% area would shift sharply to the east. In fact, there is already some evidence that there are subtle shifts in the population distribution from one year to another. A preliminary analysis of the butterflies tagged in the falls of 2001 and 2003 suggests that the center for the production of monarchs shifted eastward in 2003 as it has again this year.

For another account of Roundup Ready soybeans please visit

Figure 2. Natal origins of monarchs at overwintering colonies in Mexico. From Wassenaar and Hobson 1998.

Wassenaar, L, I. and K, A. Hobson 1998. Natal origins of migratory monarch butterflies at wintering colonies in Mexico: New isotopic evidence. PNAS. Vol. 95, Issue 26, 15436-15439


3) Monarch Waystations

You’ve done it. You’ve certified and registered over 1000 Monarch Waystations! The first thousand of what we hope will be many, many more. Our thanks to all of you who are concerned about monarch conservation and who have been willing to make the effort to create habitats for this magnificent insect.

Complete information and promotional materials are available at

I receive many emails asking whether we need more Monarch Waystations in one state or another. My answer is always yes. Given that we are losing potential monarch habitats in this country at rates of more than 3000 acres per day, we need thousands of Monarch Waystations in every state. In Oklahoma alone the loss of habitat to development exceeds 30,000 acres per year. To maintain habitats for monarchs in Oklahoma, and every other state, we must do everything we can to maintain, conserve and create monarch habitats. To reduce the loss of habitat, and create new habitats and Waystations, we need all of you who appreciate monarchs to help us get the message out. It’s all about publicity and marketing. We aren’t very good at either one and don’t have a budget to produce fancy brochures and mount a big public relations campaign. Our success to date is largely due the community of core monarch supporters. Publicity helps and you can see that coverage of the Monarch Waystation program in major newspapers can have a significant impact, e.g. Houston with 24 Monarch Waystations. An increasing number of those who participate in this program are helping by getting the local newspapers to run stories about their gardens and the monarchs they attract. As the Monarch Waystation program grows, we are seeing a shift in the locations of the Monarch Waystations from family yards and gardens, to institutional gardens (nature centers, parks, schools, etc.) - 18% of the first 300 registrations to 26% of the last 300 registrations. We expect the proportion of institutional Monarch Waystations to increase. Wouldn’t it be terrific to see thousands of schools, municipalities (such as Cleveland with 9 Waystations) and businesses add milkweeds and nectar plants to their gardens to create habitats for monarchs? They will – if we get the message out.

The distribution of the first 1000 Monarch Waystations is shown in the map below. As you can see, there are Monarch Waystations in all but 5 western states. The numbers of Monarch Waystations are highest in Texas, Michigan, Ohio, and Pennsylvania. These are critical states. All have excellent monarch habitats that are important for the development of the monarch populations each year but these states are also among the leaders in the rate of loss of habitat to development. The rapid loss of habitat in these states speaks to the necessity of promoting monarch conservation.

Number 1,000

The distinction of having Monarch Waystation #1000 belongs to the Versak-Kennedy Family of Pitman, New Jersey. You can view the complete Monarch Waystation Registry online.

Create it and they will come

You may remember Bryan Osborne of the Peterson Middle School of Santa Clara California from the July Update where his school’s creation of a monarch habitat was featured ( Bryan wrote us on the 22nd of September to say:

“We have WILD ADULT Monarchs. For the first time we here at Peterson Middle School have had our First wild Monarch butterflies emerge from chrysalis. We had 12 caterpillars on this years’ milkweed. Two adults hatched yesterday!!!! The kids are very excited!!!!! So am I!!!

Congratulations to Bryan and his students. Their diligence in creating a habitat for monarchs has and will continue to reward visitors to the garden

Bryan instructs his students in technology and one of his students, 13 year old Queenie Vo, recently posted a video online about the Peterson Monarch Project:

The students in Bryan's classes use technology to learn about monarchs and by the end of the year each student is expected to produce a video that documents their learning experience.

Visitors to Monarch Waystation #1

Our Monarch Waystation has lots of visitors and I’m slowly assembling a photo archive of the butterflies, bees, and birds seen in the garden. Here are a few photos of the butterflies seen in September:

Monarch Waystation #1 Photos


4) Monarch Monitoring at Cape May

Good Years, Bad Years and Hurricanes

The monarch monitoring program at Cape May is the longest program of its type in the United States. Initiated in 1992 by Dick Walton and Lincoln Brower, this program has provided an excellent record of the number of monarchs moving along the New Jersey coast toward Delaware. Monarchs are counted over an 8 week period each fall. The data may be found at An analysis for the first 14 years of this study was published last year (Walton, et al 2005). I was intrigued by this paper; especially by the fact that the mean number of monarchs per roadside census varied greatly from year to year. Surely there had to be a way of explaining these numbers. On the assumption that the majority of the monarchs that pass through Cape May originate in New England, with perhaps a few coming from the maritime provinces of Canada, I began examining a number of factors, such as the size of the overwintering population in Mexico, the estimated number of returning monarchs and the weather conditions in New England, to determine if any of these factors, or others, was causally related to the monarchs recorded at Cape May. To make a long story short, the only factor that seemed to be in line with the Cape May numbers was the weather in June. If it was wet and cold in June, the number of butterflies passing through Cape May in September and October was always low. It looked like there was a similar pattern for the opposite extreme. Hot dry summers were also followed by low numbers of monarchs through Cape May – with one exception 1999. The summer of 1999 was the second hottest and second lowest in rainfall in New England in the entire period and the number of monarchs appeared to be low. Yet, if you look at the records posted by the Cape May team for 1999, you will notice that the average number of monarchs jumped from 17.1 to 106.1 from week two to week three and continued to rise for the next three weeks, ending with an astounding average for the season of 328.6 monarchs per census. If the number of monarchs was truly low in New England in 1999, how could we possibly explain these numbers? The answer may be Hurricane Floyd. The image below shows the position of the hurricane on the 16th of September. Hurricanes move in a counterclockwise direction and, if you look at the sweep of the western portion of this hurricane, you can see that strong southeasterly winds covered Quebec, Ontario, New York and Pennsylvania.

Were monarchs from these western locations picked up by, or did they intentionally ride, these counterclockwise winds from western areas to the coast? It seems probable to me that this is exactly what happened especially since there were no claims from observers in New England of large numbers of larvae or adults in that region through the summer.

If we can disregard the high numbers recorded at Cape May in 1999 as an artifact of Hurricane Floyd, then the numbers reported this year are truly remarkable and support the claim by a number of observers in New England that this was the best year for monarchs in the last 30 - 40 years. The similarity of the high numbers in New England and Cape May are also consistent with the assumption that most of the monarchs passing through Cape May originate in the North East.

Walton, D., L.P. Brower and A.K. Davis. 2005. Long-term monitoring and fall migration patterns of the monarch butterfly in Cape May, NJ. Annals of the Entomological Society of America 98(5): 682-689.


5) Monarch Tagging Events

Each year to show our appreciation for the support we receive from the local residents during our spring plant fund raiser, and to engage the local community in the “Great Monarch Migration” we sponsor a public tagging event at the Haskell – Baker wetlands with the Jayhawk Audubon Society. The wetlands are nearly a square mile of low-lying lands adjacent to the Wakarusa River on the south side of Lawrence, KS. This floodplain is frequently inundated and has defied efforts to develop it. The area is the center of a major local conflict due to a plan to route a major by pass through the north side of the wetlands. Legal maneuvers have stalled the development of the K10 bypass for at least 12 years. In the meantime, numerous biologists have studied the flora and fauna of the area with great passion and artists and photographers have been busy documenting the beauty and value of the wetlands.

The wetlands are truly a wondrous place, rich with biological diversity and an absolute magnet for migrating monarchs each fall. Starting in late August but extending into October there is an abundance of flowering plants, including Spanish needle (Bidens), as well as numerous species of sunflowers and asters. Nearly all of these species are attractive to monarchs and if monarchs are in the area some are sure to be found in the wetlands. The wetlands contain at least 7 species of milkweeds and the area constitutes a major breeding site for local monarchs.

In good years, untold tens of thousands of monarchs use the wetlands as stopping points for nectar and clustering sites as they pass through the area. We schedule the tagging event for the second Saturday in September. The leading edge of the migration usually arrives in Lawrence between the 8 and 11th of September. The number of monarchs reaching the wetlands by the second Saturday varies with the weather conditions and is sometimes low if the temperatures are high and the winds have been from the southwest in the days preceding the event. But, when the weather permits and the migration is strong, as it was this year on the 16th of September, the monarch viewing and tagging can be spectacular. The plants were at their peak with Bidens, several sunflower species and an early fall aster all in full bloom.

The monarchs didn’t disappoint the crowds of taggers. By 8am the monarchs moved from the trees islands to the flowers in great numbers. After about an hour, the winds picked up causing the monarchs to cling strongly to the blossoms enabling the taggers to more easily sweep the monarchs into their nets. As the winds increased during the morning, monarchs left the flowers to seek shelter in the trees and shrubs once again enabling many taggers to sweep up small clusters of monarchs for tagging.

We received good publicity for the event and the weather promised to be favorable. We expected a crowd and we were prepared with 120 nets to loan to taggers. These nets were all in use most of the morning. The crowd exceeded our expectations and we estimated that over 500 people participated in the tagging. Many in attendance were parents or other relatives with children. Almost everyone who was issued a set of tags was successful and some groups tagged more than 100 monarchs. Many of the participants were new to tagging so I spontaneously decided to conduct “Butterfly school” presentations. I gave 14 of these presentations throughout the morning and in each I showed the participants (10-30 at a time) how to net butterflies, how to remove them from the net and handle them without injuring the butterflies, how to apply the tag and record the data, etc. It was great fun!

Photos from the Tagging Event

As the tagging wound down, one of the long-term taggers who had tagged in 2001 just after 9/11, came up to me to say she had a tag whose code ended in 911. She said she circled the number on the datasheet. I could hardly speak, there were tears in my eyes then as there are now as I write this account.

The tagging was extraordinarily successful - 2759 monarchs were tagged that morning.

The tagging day was also a big media day. I gave 4 interviews in the morning and later in the day participated in a monarch video being shot for German television by Angela Graas. Bob Pyle of “Chasing Monarchs” fame is featured in the production as he follows the monarchs from the upper Midwest into Mexico. Donald NcNeil Jr. covered the tagging event for the New York Times resulting in the following article:

NY Times Science Times, Tuesday 2 October 2006


6) Communications – A Few Statistics

I give a lot of interviews on the subject of monarchs, honey bees, pollinators, other insects, and (increasingly) on global warming. Most of the interviews deal with monarchs and Monarch Watch and there are about 3 interviews per week from late August through mid October and an average of one per week for the rest of the year. Most of the interviewers want to know how many people are involved in Monarch Watch. We really don’t know. There are many facets to our program from monarch tagging, monarch rearing in classrooms, Monarch Waystations and all of our means of reaching out to the public through the web site, our email discussion list Dplex-L, the Monarch Watch Forums, and these Updates. I tell interviewers that at least 100,000 people participate in our program each year but it is just a wild estimate. It could be more and it could be less. There are many tagging event held throughout the country each fall and we have no way of knowing how many people participate in these events. Nor is it clear how many students learn about monarchs using materials acquired from us.

We do have statistics for those parts of the project where we facilitate interactions among Monarch Watchers, as through Dplex-L and the Monarch Forums, or provide information, as we do through the Updates. The summaries below show the number of participants and the number of countries represented by the email addresses. Since not all email addresses show the country of origin, the number of countries is probably and underestimate.

Dplex-L: 473 subscribers (us, ca, de, no, jp, mx, nz, uk) N=9.

Forums: 788 registered users (us, ca, fm, mx, nz, au, uk, ar, fr, ee, tt) N=11.

Updates: 9905 subscribers (us, ca, be, de, ie, sg, ch, th, dk, pk, uk, il, nl, pl, bm, in, vn, co, no, jp, ar, br, cr, fr, es, gt, it, pt, au, tw, mx, cz, nz) N=33.

Our web site receives a fair amount of traffic – 2.25 million hits from 95,658 visits for September '06 (versus 78,134 visits for September '05 and 53,343 visits for September '04).

Then there are the email messages, too many of them - three of us respond to more than 1,000 emails/month in the fall! We try to answer as many as we can but it is taking too much time, time that we need to develop new programs. We will try to minimize the email inquiries by developing a more extensive FAQ section on our site. If you have any suggestions please let us know.


7) Degree Days for the 2006 Monarch Breeding Season

We have been following the monarch degree days through the season for five cities from Dallas to Winnipeg (Table 1) to get a sense of the environment experienced by monarchs in different regions and to be able to compare one season with another. The data in Table 1 shows this breeding season to be the hottest among the last 4 years and therefore the season with the highest potential number of monarch generations. However, as I have pointed out elsewhere, e.g. the Status of the population section of the August Update, high temperatures can be detrimental to monarchs by limiting fecundity and longevity.

Table 1. Monarch degree day totals and potential number of generations through 23 September for 2003-2006.

Year Dallas Lawrence Des Moines St. Paul Winnipeg
2003 4511.0/6.0

















2006 4854.5/6.7 3007.8/4.2 2797.3/3.9 2394.9/3.3 1700.9/2.4

Monarchs require 720 degree days to complete development from egg to egg, that is, from the time an egg is laid until a female has mated and laid her first egg. Dividing the accumulated degree days by 720 for each site gives us a way of estimating the number of monarch generations at different latitudes. At high temperatures these degree days accumulate rapidly and development can be completed in as little as 24 days. At cooler temperatures, degree days accumulate over a longer interval and generation lengths can increase to 40 and even 50 days, thus reducing the potential number of generations per season. Further, an increase in generation length has the effect of exposing the larvae for longer periods to predators, parasites and other environmental hazards that could reduce the proportion of the larvae reaching the adult stage. The formula used to calculate degree days is presented in the “Teaching with Monarchs” article in the January 2005 Update. The formula is quite easy to use. Give it a try. We are using a “modified averaging method” for calculating degree days. This method is the one most commonly used to predict the development of organisms.

If you have been following these degree day ramblings, you may remember that the method we are using to calculate degree days is based on a laboratory model developed by Meron Zalucki. The model is excellent, however, the application of temperature data from official weather stations (where the temperature is recorded at 1.5 meters rather than at .5 meters, where most monarch larvae are found) clearly underestimates the number of generations. This realization has led to the use of temperature data loggers as a way of more accurately recording the thermal environment experienced by developing monarch larvae. Our intention is to have this product available for all Monarch Watchers, and for schools, for the start of the season next year.


8) About Monarch Watch

Monarch Watch is a not-for-profit educational outreach program based at the University of Kansas. We manage several educational, conservation and research programs - focusing on the monarch butterfly, its habitat and the spectacular fall monarch migration.

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 or you can simply call 800-444-4201 (KU Endowment Association) for more information about giving to Monarch Watch.

Previous updates are available online at

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!

Monarch Watch

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