Monarch Watch Blog

Milkweed inventory – plants remaining

27 May 2014 | Author: Jim

Although we have been shipping milkweeds like crazy – about 30K so far – we still have a few – actually quite a few (22K)- plugs left that are well rooted and ready to ship. We need to find homes for these plants. The attached spread sheet shows the ecoregions from which the seeds originated and to which we will send the plants. We use the Bailey Ecoregions as a guide. We have been advised to use these ecoregions to return plants to the zones to which they are best adapted. When we can, we return the plants to the same state as the seeds originated from though the ecoregion may span several states – e.g. 251.


R. G. Bailey, Ecoregions of the United States, USDA Forest Service, revised 1994.

Please pass this around. Due to a number of miscalculations and just the shear confusion of trying to keep track of the successful production from 112 different seed lots – which in most cases was higher than anticipated, we ended up with more plugs than we expected.

Thanks for any help you can provide. The flats with plugs (N=32) are available for $60.80 each through the Milkweed Market. Shipping is included for most locations but we are finding it necsssary to expedite the shipping (with associated higher costs) to areas where the temperatures are above 90F at this time of year. (Heat damaged plants aren’t pretty).

If you are interested in plants from California, A fascicularis is still available. Again, please send an email to indicating your interest in these plants.

For additional information please visit our Milkweed Market

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Monarch Butterfly Recovery Plan

25 March 2014 | Author: Chip Taylor

The following is a memo outlining a recovery plan for monarch butterflies. On 1 March I received an email from a person well connected with monarchs asking me to prepare a document, a prospectus or memo, for business leaders by the end of the day. I was told that these persons needed background information about the monarch population along with a rough idea of what would be required to address the loss of milkweed/monarch habitat. The memo was prepared in haste and is not inclusive of all the components needed to successfully stabilize and then increase the milkweed habitats that support the monarch population. Nevertheless, this document outlines some of the basic issues. Hopefully these ideas will be useful in shaping the conversations needed to create a vision and plan as to how best to restore the monarch population. The original memo has been rewritten to improve clarity. An explanation of the estimated annual loss of habitat has been added as well.


1 March 2014

The following text is a brief summary of the status of the monarch butterfly population. The reasons for the rapid decline in monarch numbers are discussed along with a proposed recovery plan. Recovery will be possible if 1) plans can be implemented to offset the annual losses of milkweed due to development and the expansion of croplands and 2) significant efforts are made to maintain the milkweed corridor that sustains the vast majority of monarchs that reach the overwintering sites in Mexico.

A declining population
The number of hectares of forest occupied by overwintering monarch populations in the Monarch Butterfly Biosphere Reserve (and neighboring sites) in Mexico is shown in Figure 1 below. The forest area occupied by monarchs for 2013-2014 is the lowest recorded to date and continues the progression toward smaller winter numbers seen over the last decade. The decline has been attributed to three main factors: 1) the widespread adoption of herbicide tolerant corn and soybean varieties by North American farmers which has had the effect of eliminating milkweeds (the host plants for monarchs) within the crop fields; 2) the ethanol mandate passed by Congress in 2007 that increased the price of corn and soybeans which in turn led to the conversion of grasslands to crops thus elimination of the milkweeds that occurred in these areas; and 3) three consecutive years during which the reproductive success of the summer breeding population was limited by unfavorable weather conditions. The loss of habitat, i.e. milkweed and nectar plants that sustain the monarch population, is massive yet can be mitigated. In the paragraphs below I will briefly outline a vision and goals for monarch recovery and will describe the infrastructure, resources and partnerships needed to implement this recovery plan.

Figure 1. Total area occupied by monarch colonies at overwintering sites in Mexico.

Spring and summer breeding
Although monarchs can be found throughout the United States and southern Canada in the summer months, the main part of the population utilizes two critical areas with milkweeds: 1) the spring breeding area shown in Figure 2 below which encompasses most of Texas, Oklahoma, and part of Arkansas and Kansas; and 2) the upper Midwest (the eastern Dakotas, Minnesota, Wisconsin, Iowa, Illinois, Michigan and parts of Indiana). Monarchs arriving in the southern area from Mexico (in March) lay eggs on milkweeds, and the adults that develop as a result of this reproduction move northward into the summer breeding range in May and early June. This northward moving first generation spreads out over the north from the Dakotas to the Maritime Provinces in Canada. However, it is the production of the monarchs in the center of the “corn belt” that is critical. Our tagging data over the last 20 years and an earlier study using isotopes (Hobson and Wassenaar 1998, Wassenaar, et al. 1999) have shown that most of the monarchs reaching the overwintering locations in Mexico originate from this region.

Figure 2. Spring and summer breeding areas in the milkweed/monarch corridor in relation to corn acreage planted in 2011.

The milkweed/monarch corridor
These two important areas of reproduction constitute what I call the milkweed/monarch corridor. Unfortunately, it is within this corridor that a large portion of the milkweed-containing habitat has been eliminated (Figure 3). Loss of habitat in this region is likely to continue which will lead to a further decline in monarch numbers.

Figure 3. Areas of grasslands, shrub lands and wetlands converted to croplands 2008-2011. Increases in acreage by crop type are shown at the bottom of the figure. From Faber, et al. 2012.

The monarch population will continue to decline unless 1) the annual loss of habitat (.5 to 1.5 million acres**), due to conversion of landscapes to crops and development, is addressed and 2) large-scale restoration of milkweeds is initiated to offset the losses of habitat that have occurred over the last 15 years.

Vision and goals
The monarch migration can be saved if there is commitment to the two propositions outlined in the premise to 1) offset annual losses of habitat by planting milkweeds and nectar plants in areas from which they have been extirpated and 2) develop the capacity to plant milkweeds over large landscapes. Both projects require the development of greater capacity to restore milkweeds than exists at present.

Implementation of this recovery plan will depend upon the development of many different components. The program will require: 1) marketing and outreach so as to engage citizens, agencies, corporations, institutions and farmers; 2) a means of identifying landscapes on which milkweeds can be restored such as Conservation Reserve Program (CRP) lands, private lands, roadsides, federal lands, state and local parks, marginal landscapes, corporate landscapes and buffer strips; 3) a program to develop partners who can contribute to the success of the program such as nurseries, seed growers and native plant societies; 4) participants who can help with the seed collecting and plantings such as children in 4H programs, Future Farmers of America (FFA), Scouts, schools and other environmental organizations; and 5) communications with Federal, State and Local authorities to facilitate these efforts.

Capacity building and time frame and costs
In my view, the capacity to offset annual losses of milkweed/monarch habitat doesn’t exist at this time. The production of milkweed seeds and plugs (small plants) needs to increase rapidly. In addition, outreach needs to be developed and partnerships formed to get the seeds and plugs planted. By moving rapidly to implement this plan, the means to offset annual habitat losses can be developed in three years, and by the fourth year it should be possible to address the habitat losses that have accumulated over the last 15 years. Offsetting the annual habitat loss will require the establishment of at least 5-15 million milkweeds via the planting of seeds and plugs. Given the need to develop the infrastructure – seed production, etc., mentioned above, my estimate is that the yearly budget for this program should be $xxxxx million***. If more funds are available, the project could be expedited.

*This memo details what might be done to restore the monarch population that breeds east of the Rocky Mountains.

**Annual loss of habitat. One result of the ethanol mandate of 2007 has been the conversion of 24 million acres of grassland, rangeland, wetlands and shrub lands to crops. The loss by county for 2008-2011, 23,681 million acres, is shown in Figure 2. An additional 400,000 acres were converted to crops in 2012 bringing the total to more than 24 million acres. Figures for the conversion of grasslands (much of it retired CRP land) to croplands for 2013 are not yet available. Although the rate of conversion to croplands may be slowing down, Congress has mandated a further reduction in the CRP program with a cap at 24 million acres by 2017. The bottom line is that milkweed-containing habitats within the farming sector will continue to decline but – by how much? Annual losses of .5-1.5 million acres are likely but these estimates are based on a number of assumptions as follows:
1) Conversion of grassland and retired CRP lands to croplands will continue at rates of 350-450 thousand acres per year.
2) Loss of habitat due to development will continue. The annual conversion of landscapes in the United States to building sites and the expansion of cities is in excess of 2 million acres per year. Much of this development, perhaps 500,000 acres, occurs in the monarch summer breeding range. Other losses, perhaps 100,000 acres per year, are occurring in monarchs’ spring breeding range.
3) Losses outside the corridor will continue and these losses will also have a negative impact on monarch numbers.
4) There are additional losses of milkweed/monarch habitats that are not easily accounted for such as land management decisions that eliminate milkweeds and other forbs from pasturelands, roadsides and other land parcels.
5) Lastly, this interpretation assumes that the price of corn will remain in the $4-$5/bu range. Higher prices are likely to result in the conversion of more milkweed containing habitats to croplands.

It should be clear that, although the figures for the annual loss of milkweed/monarch habitat are not firm, it is likely that these losses will be close to a million acres per year for the foreseeable future.

***I have not prepared budget for this project. As you can see from the above, capacity building and implementation are both complicated and will require a major effort from many participants. Suffice to say, the annual cost of this program will be many millions. The project needs to be refined more precisely before dollar figures can be assigned to the different cost centers.


Cropland conversion. 2014. (accessed 28 January 2014).

Faber, Scott, Soren Rundquist and Tim Male. 2012. Plowed Under: How Crop Subsidies Contribute to Massive Habitat Losses. Environmental Working Group (accessed 28 January 2014).

Hobson, Keith A., Leonard I. Wassenaar and Orley R. Taylor. 1999.
Stable isotopes (dD and d13C) are geographic indicators of natal origins of monarch butterflies in eastern North America. Oecologia (1999) 120:397±404.

Wassenaar LI, Hobson KA. 1998. Natal origins of migratory monarch butterflies at wintering colonies in Mexico: new isotopic evidence. Proc Natl Acad Sci 95:15436±15439.

For further information about monarchs, milkweeds and Monarch Watch, please visit

Further commentary

Obviously, mitigating the decline in the monarch population will require a great deal of discussion. In the above I’ve only addressed what it might take to mitigate the annual losses of milkweed monarch habitat. The larger issue is how to restore sufficient habitat so that the overwintering monarch population will be large enough, and will survive in sufficient numbers to repopulate the milkweed/monarch corridor each year. There is a history of catastrophic mortality at the overwintering sites (70-80% losses due to winter storm in 2002 and 2004). The large overwintering populations of 2001-2002 (9.35ha) and 2003-2004 (11.12ha) survived in sufficient numbers to recover from these losses in two years. Overwintering populations of a hectare or less will not fare as well should they experience such mortality. The recovery would take much longer. How can the latter scenario be avoided? My interpretation is that – at a minimum – our larger target should be to provide sufficient milkweed/monarch habitat to sustain populations of 4 hectares or more from year to year. Even with high winter losses such populations should be robust enough to repopulate the United States in the spring.

There are more questions of course. What are the near and long term goals? How much will the project cost and where will the funds come from? Will public funds be available? Will corporations, foundations, environmental organizations and private individuals support this effort? How will the funds be administrated? Who are going to be the partners in this enterprise and who will take the lead in coordinating the implementation of this program?

There are lots of questions; monarchs need the answers.

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Monarch Population Status

29 January 2014 | Author: Chip Taylor

The overwintering numbers are in from Mexico and once again it’s bad news. The numbers are not a surprise; as early as May, we predicted that the population would be lower this winter. I’ll discuss our reasons for this expectation and the overall decline seen throughout the last decade, but first, let’s look at the numbers reported by World Wildlife Fund, Mexico.

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

Habitat Loss

In previous postings to this Blog I’ve mentioned three factors that have contributed significantly to the loss of monarch and pollinator habitats: the adoption of herbicide tolerant (HT) crops, the ethanol mandate, and development. In my lectures I’ve presented figures in which I try to quantify the loss of habitat attributable to each of these factors. The expected low numbers of monarchs in Mexico this winter have caused me to reevaluate and clarify these losses. My interpretation is summarized in the two tables below. The loss of monarch habitat due to the adoption of HT crops and the ethanol mandate is summarized in Table 1. The overall loss of monarch habitat is shown in Table 2.

Let’s deal with the HT crops first.

Year Corn & Soy Acreage Event
1996 143.5 million First HT Crops
2006 153 million Before Ethanol
2007 158 million Ethanol Mandate
2012 169 million Conversion Continues
2013 174.4 million Conversion Continues
Bottom Line: 29.5 million more acres of C&S in 2013 than 1996. Of this acreage >24 million represent former CRP, grassland, rangeland, and wetland habitats.

Table 1. Loss of Monarch Habitat due to HT Crops and Biofuel Initiative

If you have been following postings to this Blog, you know that row crops (e.g., corn and soybeans) contained relatively small quantities of common milkweed when tillage was used to control weeds in these fields. Some milkweed survived and a survey conducted in 2000 (Oberhauser, et al 2000) showed this habitat to produce more monarchs per acre than other milkweed/monarch habitats. With the adoption of HT crop lines, the use of glyphosate has all but eliminated milkweeds from these habitats (Brower et al 2011, Brower et al 2012, Pleasants and Oberhauser 2012 and personal observations).

One of the startling aspects of the corn and soy dynamics is the increase in acreage over the last 17 years. In 1996 the total acreage for corn and soy was 143.5 million acres while in 2013 was 174.4 million acres – an increase of 29.5 million acres. Note that while the acreage increased by 9.5 million acres from 1996 to 2006, the acreage increased by 20 million over the last 7 years. This increase is largely due to the ethanol mandate. Early in 2007 congress passed the Clean Energy Act of 2007, frequently referred to as the ethanol mandate. It was apparent to many growers in the spring of 2007 that this act was going to increase the demand for and price of corn. Corn planting has been increasing ever since with the result that farmers have removed hedgerows and narrowed field margins. In much of the corn-belt, farming is from road to road with little habitat for any form of wildlife remaining. Grasslands – including some of the last remaining native prairies, rangelands, wetlands, and 11.2 million acres of Conservation Reserve Program (CRP) land – have been plowed under to produce more corn and soybeans. Most of these acres formerly contained milkweeds, monarchs, pollinators and other forms of wildlife. They are gone and the total loss of these habitats since 2008 exceeds 24 million acres (an area about equal to the state of Indiana).

Development consumes about a million acres of farmland a year and the conversion of woodlands and other landscapes to shopping malls, housing and roadways consumes another million acres a year. Overall, the loss of various habitats due to development probably exceeded 34 million acres since 1996. Some of this habitat was in the West and since we are just considering the eastern monarch population, I’m estimating the total loss due to development to be 17 million acres. Not all of these landscapes contained milkweeds but much of it did at one time. There are also habitat losses due to excessive mowing and use of herbicides along roadsides. In an earlier study (Taylor and Shields 2000) we showed that the area from the edge of the road to the edge of the field was about 1% of the total land area in most eastern states. These were significant milkweed and monarch habitats in the past but it appears that much of this habitat has been lost as well due to these practices. Unfortunately, there is no way to estimate this loss.

I’ve summarized the total loss of habitat in Table 2.

Factor Acres
HT corn & soybeans >150 million
Development +/- 17 million
Total >167 million*
*Represents >30% summer breeding area

Table 2. Habitat Loss

My conclusion is that at least 167 million acres of monarch habitat has been lost since 1996. Not all of the corn and soybean acreage occurs within the summer breeding range for monarchs so the total loss of monarch habitat due to HT crops is lower (150 million) than the total area (174.5 million) planted in 2013. The 24 million acres of grasslands, etc. converted to croplands since 2008 have been included in the estimated loss to HT crops. Add to this number the estimated loss due to development and the total is 167 million acres lost but this could easily be an underestimate since there are losses such as roadside management that we can’t account for. To give you some perspective on the area that is represented by this figure, consider the following: 167 million acres =261 thousand square miles – an area just below the total acreage of MN, WI, IA and Il (266 thousand square miles) and Texas (266 thousand square miles).

The total summer breeding range for monarchs is probably 800-900 thousand square miles. If it is true that 261 thousand square miles of this range no longer contains milkweeds and nectar plants for monarchs, it would mean that 29-33% of the monarch breeding range has been lost. This loss is calculated based on the entire summer breeding range. A more refined approach confined to the states and the region of southern Ontario that produce most of the monarchs that reach Mexico is likely to show that the loss in these areas is much higher. Have I overestimated these losses? Maybe – but probably not. In any case, due to the economic forces involving crop production and human population growth, these losses will continue. It is clear that if our goal is to save the monarch migration, we must find a way to mitigate the loss of monarch habitat.

Reproductive Success

In a long article posted to the Blog on the 29th of May 2013 (“Population Status“), I discussed the prospects for the development of the monarch population over the coming months. The article started as follows:

“Monarchs are off to a slow start this year, with the number moving north in May at an all time low (as indicated by first sightings reported to Journey North). In the following paragraphs I’ll explain why this will be a lean year for monarchs and why the overwintering population in Mexico could be even lower this coming winter than it was in 2012-2013. Predicting whether monarch populations will increase or decrease would seem to be risky or even foolish but, as you will see, there are patterns that support these predictions based on: 1) overwintering numbers; 2) first sightings in the spring (1997-2013); and 3) the impact of temperature on the development of the first generation immature stages and the ability of adult monarchs to move northward to recolonize the breeding areas in the northern states and Canada.”

The above was followed by a long explanation of the patterns of first sightings and comparisons of the numbers of first sightings and temperatures during the breeding season for other low years. I concluded with the following summary:

“So, what does this tell us about what to expect in the fall and winter of 2013? Let’s deal with the number of observations first. Although, the number of first sightings reported in 2013 is similar to those of 2004 and 2005, the number of people reporting first sightings has increased significantly since reporting of first sighting began in 1997 (Howard and Davis 2004). In other words, fewer monarchs have been seen this year by a larger group of observers – suggesting that the number of returning monarchs was lower in 2013 than in 2004 and 2005 (both low returning populations) or even 2010, which saw the lowest overwintering population (1.92 hectares) prior to that of this past winter.

There is a similarity between 2013 and 2004 – the monarchs will arrive late in the northern breeding areas. The mean temperatures for March (-2.0F) and April (-2.7F) were the lowest for these months since 1996 and the April temperatures in particular slowed development of immature stages. May temperatures – which in most of the South Region are near or just below normal – have not appreciably aided northward movement of first generation monarchs. The result of all of these factors is that the arriving number of first generation monarchs will be low and they will arrive late. Even if this projection is true, is there a chance that the population can rebound as it did in 2005? Yes, but the temperatures in nearly all of the northern breeding range will have to be above normal by 2-3F throughout the summer for the population to increase. If the temperatures are normal (and normal summer temperatures are projected by NOAA for the upper Midwest (see the National Weather Service’s Climate Prediction Center), the overwintering population is likely to be in the range of 1 hectare again this coming winter and could be much lower.”

As it turned out – all of the above came true. The monarchs did arrive late in the summer breeding areas. The number of arriving butterflies was also low. In the northeast temperatures favored nearly on time arrival of the colonizing butterflies but extensive periods of cool, rainy days limited reproductive success. The conditions were so poor for reproduction in the northeast that it became clear in August that the number of monarchs that would be recorded at Cape May, New Jersey, during the migration would be quite low and it was (third lowest recorded since 1992). NOAA was right on target with the temperature predictions too. Normal temperatures were experienced throughout the northern areas – not the higher than normal temperatures that were needed to increase the population. The delayed arrivals apparently resulted in a late migration at the end of the season. Throughout the fall we kept hearing how late the migration was. In Lawrence, KS we had some on time arrivals, a rather small number, followed by a bit of a delay and then a flush of late migrants. In a year with an early onset of freezing weather many of these migrants would not have survived. But it was a warm fall and they kept moving, arriving later than usual in the vicinity of the overwintering sites in Mexico.

Every year is unique but some years deviate more than others from the norm. 2012 and 2013 both deviated from normal with 2012 being too hot and 2013 being too cold at critical times, and both resulted in low overwintering numbers. We break the breeding season into three intervals: March-April, May- 9 June, and June-August. The temperatures in 2012 were higher in each of these intervals than for any of the last 18 years. In 2013 the temperatures were lower than normal for the first two periods. However, it was the lower than normal temperatures in April that slowed development of immatures, and somewhat cooler May and early June that delayed the recolonization of the summer breeding areas.

Monarch numbers will rebound but only if the weather allows AND there is enough milkweed to increase the population. While we will never get back to the large populations of the 1990s, there is still enough milkweed to produce monarchs in sufficient numbers to colonize 3-4 hectares of the forests in Mexico. However, given the current size of the overwintering population it is likely that it will take 2-3 years with relatively favorable breeding conditions for the population to attain such numbers.

Looking ahead, NOAA is predicting higher than normal temperatures for Texas in March and April – which wouldn’t be good. On the other hand, some of the weather services are projecting normal temperatures through mid-March. That sounds better to me. Let’s hope there are favorable conditions for monarchs over the next several years. While waiting for conditions to improve, let’s plant milkweed – lots and lots of it.

I wish to thank Vijay Barve, Janis Lentz, Elizabeth Howard for help determining the patterns described above and to Jim Lovett for his assistance on the figures and formatting of this Blog entry.


Brower, L.P., Taylor, O.R., Williams, E.H., Slayback, D.A., Zubieta, R.R. & Ramirez, M.I. (2011) Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk? Insect Conservation and Diversity, 5(2): 95-100.

BROWER, L. P., TAYLOR, O. R., WILLIAMS, E. H. (2012) Response to Davis: choosing relevant evidence to assess monarch population trends. Insect Conservation and Diversity (2012) 5, 327–329.

Pleasants, J.M, Oberhauser K. S. (2012) Milkweed loss in agricultural fields due to herbicide use: Effect on the Monarch Butterfly population. Insect Conservation and Diversity (March 12, doi: 10.1111/j.1752-4598.2012.00196x)

Oberhauser, K.S., Prysby, M.D., Mattila, H.R., Stanley-Horn, D.E., Sears, M.K., Dively, G., Olson, E., Pleasants, J.M., Lam, W.F. & Hellmich, R. (2001) Temporal and spatial overlap between monarch larvae and corn pollen. Proceedings of the National Academy of Sciences USA, 98, 11913– 11918.

Taylor O R, Shields J. The Summer Breeding Habitat of Monarch Butterflies in Eastern North America. (2000) Washington, DC: Environ. Protection Agency.

Notes: The figure (24 million acres) for the conversion of grassland, rangeland, wetlands and former CRP lands to cropland was obtained from two sources: Faber, Rundquist and Male (2012) data obtained from a USDA website summarizing cropland conversion in 2012 (2013). The former showed that 23.6 million acres had been converted to cropland from 2008 through 2011 and the later indicated that 398,223 acres had been converted in 2012. No figures are yet available for these conversions in 2013.

Plowed Under: How Crop Subsidies Contribute to Massive Habitat Losses (2012)
Scott Faber, Soren Rundquist and Tim Male. Environmental Working Group (accessed 28 January 2014).

CROPLAND CONVERSION (accessed 28 January 2014).

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Importance of Monarch Conservation

24 January 2014 | Author: Jim

by Candy Sarikonda, Monarch Watch Conservation Specialist

I am a nurse. A mother. A lover of nature. I want to make this world a better place.

And monarchs are helping me do just that.

Monarch conservation is important for many reasons. First, conserving and creating monarch habitat will help many of our pollinators. Every third bite of food we eat comes to our table courtesy of a pollinator. Monarchs, bees and many other pollinators share much of the same habitat—so what happens to monarchs, happens to other pollinators. Monarchs are an indicator of the damage done to our environment—we can count them as they gather by the millions in Mexico. They are an indicator of what we cannot fully quantify—the loss of our pollinators and their habitat. We need to protect all of our pollinators—the many bees, birds, bats, and other insects that provide us with pollinator-services and ultimately put food on our table. Do you like blueberries, strawberries, raspberries? How about watermelon, apples, bananas or squash? Chocolate? Then thank a pollinator!

Monarchs are a flagship for conservation. The Monarch Joint Venture explains this well Monarchs engage children and adults in conservation efforts. By participating in the monitoring of monarchs through citizen science programs, or simply experiencing the joy of raising a monarch at home or in school, children get direct experience with nature and develop the strong connection with nature that will lead to their development as conservationists of the future. According to the Nature Conservancy, conservationists point to a childhood experience with nature as the most important factor that led to their environmental activism as adults. In an increasingly urban society, we need to keep giving children direct experiences with nature that will foster their development into conservationists.

We know that exposure to the natural world can produce significant health benefits. Exposure to nature has been shown to decrease stress and anxiety, lower blood pressure, reduce obesity, reduce symptoms of Attention Deficit Hyperactivity Disorder, and promote a general sense of well-being. Citizens who understand the connection between themselves and the natural world understand the importance of caring for themselves and their environment. By participating in projects designed to monitor monarch populations, citizens can witness the effect that pesticides and loss of habitat have on pollinators. And they can see how the loss of pollinators ultimately affects them.

Monarch conservation can also help develop an interest in science. Engaging students in exploration and observation of the natural world will help them develop the skills critical for the development of our future science and technology leaders. In a global market, the U.S. cannot afford to lag behind many other industrialized nations in the preparedness of our students for careers in science, technology, engineering and math (STEM). We need to get our youth interested in science; to make it fun and exciting for them; and help them build the confidence they need to succeed in their chosen STEM career paths. Exposure to the natural world helps children develop social skills, improve critical thinking skills, develop self-initiative, develop self-confidence and improve creativity. These are the skills needed by successful STEM leaders of the future.

Each and every one of us must do our part in conservation of our natural world. Conserving the monarch migration is one way to make a difference. There are many ways to help monarch butterflies. We must create, conserve, and restore monarch habitat—we need to plant milkweed. And not just milkweed, but many other host and nectar plants that support our bees, butterflies, and birds. It is OUR responsibility to restore habitat. No one person can do it alone—it takes a village. If every person in this country planted just ONE milkweed, we would have 300 million more milkweed plants than we do now. It starts with education—educating people that monarchs are in decline; that they only feed on milkweed; and that we can collectively do something to help them. We need to make a conscious effort—educate ourselves, find out what monarchs and other pollinators in our home gardens and park preserves love, and plant it; instead of growing plants with no pollinator-value. We can reduce mowing of roadsides and other suitable plots of land, and demonstrate the cost savings. Eliminate needless lawn and plant pollinator-friendly plants. Get involved in citizen science programs. Be of service and volunteer.

We need to reduce pesticide and herbicide use. Pesticides kill insects, and can harm or kill monarchs. But they can also harm humans. According to the American Academy of Pediatrics, a growing body of evidence indicates the negative health outcomes that can arise from exposure to pesticides during childhood Scientists have noted the effect that pesticides and herbicides have had in animal models, and have documented evidence of their impact on human health in farming communities. We have seen increased rates of depression and Parkinson’s disease in farming communities. In California’s Central Valley, farming towns are referred to by some as “Parkinson’s Alley,” for their higher than average incidence of this debilitating neurological disease Yet, with the advent of GM crops, we have seen an increase in the use of herbicides, the development of superweeds, and the use of more and more potent chemicals It is time to reexamine the way we farm, and how we use pesticides/herbicides in our daily lives. Clearly, limiting herbicide and pesticide use will not only be good for monarchs—it will be good for human health as well.

We need to contact our legislators and support legislation that protects pollinators and their habitat. The Farm Bill is an important piece of legislation that can be used to support the creation of pollinator habitat in the form of Conservation Reserve Program (CRP) land. We need to encourage our legislators to support provisions in the Farm Bill for the creation and maintenance of CRP land. According to the Ohio Department of Agriculture, over one billion bees, or nearly 75% of Ohio’s honeybees, have been lost to Colony Collapse Disorder. An untold number of native bees have been lost as well. Crops left unpollinated could result in over $80 million in lost revenue per year for Ohio’s specialty farmers alone. We must let our legislators know we support efforts to conserve pollinator habitat via the Farm Bill and other forms of legislation. We need to educate and empower our fellow citizens to do the same.

We need to work with the private sector, and encourage companies to adopt business practices that will conserve natural resources. We must convince companies that investing in “green capital” is not just the morally right thing to do—it is the only thing to do. Investing in our natural resources is a necessity for many companies to continue their business practices. According to Mark Tercek, CEO of the Nature Conservancy, nature is not a luxury—it is an investment.

As conservationists, we must focus on bringing newcomers to the conservation table, engaging the general public in our conservation efforts. We cannot continue to “preach to the choir.” Monarchs bring people to the table. No monarch conservation organization simply promotes monarchs only. Monarchs are the focus of course, but the ultimate goal is conservation—of both humans and wildlife.

In any endeavor, it is important that we all work together. We must focus on what unites us, rather than on what divides us. We will have different ideas, different experiences, and different viewpoints. But we must find common ground, and use our differences to make us stronger. It will take many hands to secure the future, both for the monarchs and ourselves. We must present a united front. This is something that partners in monarch conservation have known for years — Monarch Joint Venture partners united in one effort, ultimately to protect the environment and humanity.

How did we get from monarch conservation to the subject of pollinator habitat, human health, green capital and STEM rankings? It’s simple. Humans do not exist separately from nature. The term “The Web of Life” is not just a flowery cliché. It is reality. Everything is connected. Everything.

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A Bit of Monarch History

24 January 2014 | Author: Jim

by Ilse Gebhard, Monarch Watch Conservation Specialist

I recently received a folder labeled “National Butterfly” from a Kalamazoo Area Wild Ones member. He had found it while working on a project documenting the history of Michigan State University’s Kellogg Biological Station in Augusta, Michigan.

The contents of the folder covered an aspect of monarch history all new to me, as it occurred in 1989, about 10 years before I really became involved with monarchs and 3 years before the founding of Monarch Watch.

For its 100-year anniversary in 1989, the Entomological Society of America (ESA) decided that the country needed a National Insect and they voted the monarch as its choice, representing about 600 species of butterflies and at that time nearly 90,000 other insect species that are an integral part of the natural heritage of the United States. They were well aware, nearly 25 years ago, that monarchs were declining in numbers under pressure from urbanization and loss of habitat resulting in the reduction of milkweeds and overwintering groves of trees in California and Mexico.

ESA put out a very nice colored brochure covering monarch history, biology, migration, ecology, and conservation of overwintering sites. The brochure includes a very impressive list of sponsoring organizations:

• Entomological Society of America (ESA)
• American Registry of Professional Entomologists
• American Institute of Biological Sciences
• Connecticut Entomological Society
• Lepidopterist Society
• National Audubon Society
• National Wildlife Federation
• New York Entomological Society
• The Nature Conservancy
• The Wildlife Society
• Xerxes Society

In addition the folder contains letters of support from:

• Kentucky Academy of Science
• American Association of Zoological Parks and Aquariums
• The American Entomological Society (AES)
• Kansas Associated Garden Clubs, Inc.

The ESA apparently worked very hard to promote the monarch as National Insect. The contents of the folder (the brochure plus 9 pages) were a packet of info that they sent out to various organizations asking them and their members to support this endeavor. One such organization was the Kellogg Bird Sanctuary, as per cover letter in the folder.

To me the most interesting document in the folder is a copy of H.J. RES. 411, a Joint Resolution introduced into the House of Representatives on September 27, 1989 by Representative Leon Panetta from California. Representative Panetta was born in Monterey, a well-known overwintering site of the Western US monarch population, and was elected from his native district. It was referred to the Committee on Post Office and Civil Service and by January 31, 1990 it had nine cosponsors. Not having found any further info on the resolution by a web search, I assume it died for lack of cosponsors.

The above-mentioned letter of support from the Kentucky Academy of Science states that they will pursue the adoption of the monarch as the State Insect. I guess that was not to be either, as a web search shows the viceroy to be its State Insect adopted in 1990 – close, but not the real thing. On the other hand, the monarch is the State Insect of Alabama, Idaho, Illinois and Texas and the State Butterfly of Minnesota, Vermont and West Virginia. Interestingly, 15 states have the non-native honeybee as their State Insect, 1 state lists it as their State Bug, and 2 states list it as their State Agricultural Insect. Five states have neither a State Butterfly, Insect or Bug.

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North Florida Monarch Overwintering Count

24 January 2014 | Author: Jim


Richard G. RuBino
August 2013

Summary: For years monarchs have been seen along the northern coast of the Gulf of Mexico during January and February, but few attempts to document these sightings have been made. In recognition of this need, a count was undertaken in January and February 2013 to determine the degree of overwintering, if any, along the coast of the eastern end of the Florida Panhandle. The project focused on two questions: do monarch butterflies overwinter along the northern Gulf coast and does milkweed survive northern Gulf coast winters? Sub-questions included: if so, where and at what intensities? The answer to both questions is yes — sometimes. The study found both monarchs and milkweed across the entire length of a four-county coastal area, but the survival of the former is highly dependent on the benevolence of mankind.


Map 1 (PDF file): Observed Locations of Milkweed in the Big Bend of Florida, January-February 2013

Map 2 (PDF file): Observed Locations of Monarchs in the Big Bend of Florida, January-February 2013

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Moving for Monarchs (M4M)

19 December 2013 | Author: Chip Taylor

“Moving For Monarchs” started with an email I received on the 20th of March. My inbox is flooded with emails, so many that I can’t answer them all (and to those of you that I haven’t gotten back to – I apologize). I make a special effort to try to get back to journalists in a timely manner and, when I received an email with the subject line “Hoping to speak with you”, I thought it might be from a journalist and I opened it. To my surprise, it was an offer to assist in publicizing the need for monarch conservation from a 21 year-old dancer, actor, and writer by the name of Gwynedd (pronounced Gwyneth) from New York City. I found the letter to be quite compelling, and Gwynedd and I arranged to talk one Sunday afternoon. The idea of using dance to communicate the importance of monarch conservation was intriguing, but I was skeptical. I didn’t have a clear vision of how this might work and, as with any creative process, Gwynedd needed time for her initial idea to develop and emerge. We spoke many times over the next few months, mostly when I was working in the lab on Sunday afternoons. These were good times to talk since were no interruptions and I did a lot of listening as Gwynedd explored various ideas and tried to bring together a team that could help her fulfill her vision. Late in the spring, the team began to come together, and we started planning how to arrange for Gwynedd and her production crew to come to Kansas to film her first monarch conservation video. I made arrangements with my neighbors Dan and Linda Haney to do some filming on their property and through Dr. John Briggs to conduct most of the shoot on the Konza Prairie just outside of Manhattan, Kansas.

monarch-population-figure-monarchwatchGwynedd testing her wings on the Konza Prairie (23 June 2013). Photo by Chip Taylor.

Gwynedd and her Moving for Monarchs crew arrived in Lawrence for a photo shoot and interviews at Monarch Watch on the afternoon of the 21st of June. Late in the day, we drove to the Konza Prairie to view the shooting locations planned for the next two days. Flowering in the prairie was at its peak with literally thousands of butterfly weeds (Asclepias tuberosa) and other milkweeds in full bloom. The weather during the shoot was iffy with strong winds. Splashes of sunlight scattered over the landscape though gaps in rapidly moving multicolored clouds – some of which shed a tear or two on the prairie. We worked around the rains and the winds and completed the filming late on Sunday the 23rd of June. What followed the trip to Kansas is best told by Gwynedd. The process of post production was long and complex. Gwynedd and Gabriella (the Director of Photography) live in NYC and Washington D.C., respectively, so the process involved a number of bus and train rides as well as extensive online file sharing–tasks completed on a volunteer basis by the young artists. Throughout these stages, Gwynedd and team carried on – working on the project whenever they could while also developing the promotion for the Kickstarter project. I can’t wait for you all to see the film–it speaks to awakening the need to conserve the monarch migration.

Below is the letter that made me Move For Monarchs.

Date: Wed, 20 Mar 2013 22:34:04 -0400
Subject: Hoping to speak with you
From: Gwynedd Vetter-Drusch

Dear Professor Taylor,

I am writing to you after having read the article “Monarch Migration Plunges to Lowest Level in Decades” from the New York Times last week. I would like to take positive action to raise awareness and implement solutions, such as those you have proposed in your latest blog post (including the planting of large amounts of milkweed) in order to counteract the effects of loss of monarch habitat.

I am a 21 year-old dancer, actor, and writer living, studying, and working in New York City. However, I have not always lived in New York. I grew up, in fact, in the small town of Manson, Iowa. My family moved to Manson from Seattle, WA, when I was about nine years old. It was in Manson that I discovered monarchs.

As a child I roamed our family farm (my family has been farming in the area for four generations), including a seven acre pasture which has never been tilled. They say you can still see the stagecoach tracks where the stagecoach used to run through those seven acres. This pasture sat on the edge of town, just across from Rose Hill Cemetery.

During the hours I spent outside in the summertime, I noticed that dozens of monarchs would fly back and forth across the road from the pasture to the cemetery and back again. One day I followed them from the pasture, which was full of milkweed, to the cemetery.

There I saw one of the most beautiful things I have ever seen. As I walked down a row of the largest old trees in the cemetery, I realized that the leaves on the branches were shifting and moving. When I came closer, I discovered that the leaves were actually butterflies, turning the branches a rusty orange. It was a large group of butterflies, I would say over a hundred monarchs at least (though to me the numbers seemed even greater), and they had situated themselves on the branches.

If you walked among them or moved a low-hanging branch, the world around you would explode in fluttering orange.

I cannot fully describe the effect that this and other experiences with monarchs have had on me. But those encounters have shaped my work as a performing artist, have been the subject of my poetry and a children’s book I am working on, and have had a profound impact on who I am as a person.

Throughout middle school and high school, I attended various science and environmental leadership camps through the University of Iowa and Northland College (in Ashland, WI). Biology was one of my favorite subjects, and Rachel Carson became one of my personal heroes. However, over time and through some surprising events, my focus shifted to the study of classical ballet, and that took me from Iowa to New York City at the age of 17.

Yet, I have always carried the memory of monarchs with me. Their delicate strength—their ability to migrate so far on seemingly paper-thin wings—has often been the source of personal inspiration when I encountered difficulties throughout my dance studies. In fact, the parallels between monarchs and ballet dancers are striking. Not least among these is the physical transformation of butterfly from earth-bound caterpillar to flying creature, which is like the transformation of dance student to full-fledged dancer, capable of performing amazing physical feats—including hanging for a moment in suspension in the air:  flight.

Perhaps this seems to romanticize a living organism, but in a way monarchs have a sort of mythological appeal. They are these incredibly beautiful, vulnerable creatures who go on a migration journey. I believe that this is one level that every person can relate to, and it is on this level that even those who do not understand the inherent worth of a species in its rightful function within a living system can begin to understand. And they can be inspired to take action.

I feel strongly compelled to take action myself, and as I lay awake in bed for several hours the night after reading the article, an idea came to mind, and I could not sleep until I had gotten out of bed and written down the details. I have been continuing to develop it since then.

I see a way to raise awareness of the problems facing monarchs and help Monarch Watch and other groups in their efforts to solve the problems. What I see combines the art forms of dance and photography (and perhaps film) and the power of the internet in a way that makes the issue highly visible.

I would be very interested in starting a conversation with you about this idea, either by phone or by email, whichever you prefer.

I can be reached at the following number, or at this email address.

Gwynedd Vetter-Drusch

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The Northward Migration: when does it end?

24 June 2013 | Author: Chip Taylor

There are numerous unanswered questions about monarchs. What causes the migration to start in the fall? Why do they fly to Mexico? Why do the overwintering colonies form where they do? Why do the monarchs halt their southern flight at 19.5N? Why not go further? These, and other unanswerable questions, are asked of us frequently. We have to admit that we don’t know the answers but offer speculation and a best guess when we can. Curiously, though many of those we talk to know that monarchs do not continue to migrate through the heart of the breeding season, no one asks – when does the northward migration end in the spring and early summer? Well, it’s a good thing no one asks that question — because we don’t know the answer to that one either.

So when does the northward push by first generation monarchs* end? If there is a celestial component to when monarchs stop moving such as day length or the rate of change in day length or some other factor, is it possible for monarchs to arrive too early in the northern latitudes such that they fly beyond the limits of milkweed? Or, the converse, do conditions during some springs limit northward flight such that the monarchs do not reach the northern limits of milkweeds? In other words, is it possible during extremely cold springs that the “stop signal” whatever it is, is perceived before all the breeding habitat is effectively colonized? I think both things happen but I can’t argue effectively for these possibilities because there is virtually no data on this subject and relatively few credible observations. Years ago I directed one of the undergraduate students I was working with to make daily observations of directional flight by monarchs moving through this part of eastern Kansas in late May and early June. To our surprise, all directional flight appeared to end around the 5-7th of June. Monarchs present in the area were decidedly non-directional after the 7th. Day length is 14h 49m here on the 7th but the amount of change per day is declining rapidly (47 seconds from 7th to 8th) as we approach the summer solstice on the 21st. On that day the daylight period is 14hrs and 54 minutes.

This observation raises some questions. Do monarchs stop moving when the rate of change in day length drops substantially below a minute per day, and does this mean that monarchs stop directional movement progressively with increasing latitude?

The day-to-day differences become progressively smaller as one approaches the equinox. For example, at Duluth, MN, day-length increases by 25 seconds on the 14th and by only 11 seconds on the 18th.

Let’s see what happens at different locations as we move northward:

Daylength in June
Lawrence, KS
14h 49m
14h 54m
7th-8th 47 seconds
Des Moines, IA
15h 06m
15h 12m
7th-8th 48 seconds
St. Paul, MN
15h 30m
15h 37m
9th-10th 48 seconds
Duluth, MN
15h 45m
15h 52m
9th-10th 49 seconds

Note that the rate of change (less than 50 seconds per day) shifts from the 7th to 8th for Lawrence to the 9th-10th for St. Paul. Thus, if migration northward ends as a function of latitude and rate of change per day, we would expect the most northerly monarchs to still be showing directional flight even though directional flight has stopped further south.

This is certainly an interesting possibility but we need data and, as I said, there is virtually none. So here is where those of you making observations of first sightings can help. If you see a monarch, note its flight behavior. Is it nectaring, searching for oviposition sites or is it showing directional flight? And, if it is showing directional flight, what direction is it moving – that is, what is its compass bearing (approximate bearings would do for a start**)? Directional flight is particularly difficult to observe in the spring. In most cases the butterflies are flying quite fast at a height of 3-4 meters. If you are driving on east -west roads during May and June look for monarchs crossing in front of you from S to N (or NE) at a height just above your car or pickup.

Observations of directional flight are valuable and will further our understanding of monarch behavior. Such observations could be shared with our email discussion list (Dplex-L) or reported to Journey North. Systematic studies by students or even groups of citizens of directional flight over a series of weeks in the spring and early summer at different latitudes could resolve this question. An alternative approach would be experimental releases with monarchs that had been reared under specific natural conditions or by using a flight simulator.

*First generation monarchs are offspring of monarchs that overwintered in Mexico. The first of these monarchs begin moving north in the last week April, with most moving north in May and early June.

** Many smart phones have a compass app available to them. To obtain the bearing of a monarch moving directly away from you, point the phone at the monarch and take a screen shot of the compass. The image should be time-stamped and may even include latitude and longitude so it can be reviewed later.

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The Milkweed Gamble

21 June 2013 | Author: Chip Taylor

I’m not a gambler but I gambled this spring with milkweed production. The question/gamble was – if we produced 25, 000 milkweed plugs, could we get people to buy them? I thought we could but, if we couldn’t, the money invested in the production of the plugs would be lost. I worried about it – a lot.

Our partner in this enterprise was Applied Ecological Services (AES). Working with Elliott Duemler, manager of the Kaw River division of AES in Baldwin, KS, we planned the production of milkweeds suitable for states from coast to coast. This production was enabled by the collection of seeds of numerous milkweed species from specific regions of the country by many volunteers. Tori Pocius, our milkweed coordinator at Monarch Watch, processed, cataloged and stored each batch of seed. When it came to making decisions on what to propagate and how many plugs to produce for each area, we checked the seed sources, decided which to use and then we guessed at the number of seedlings to produce for each region. Sometimes we over produced, sometimes we hit the mark and other times propagation failed or too few seedlings were produced to provide an adequate number of plugs. Propagation of milkweeds is not an exact science and some batches of seed fail to germinate under the best of conditions. Overall, production of seedlings was excellent and the next step was to transplant these seedlings and grow them out to the plug stage. Again, it was a guessing game – how many orders might we expect from each region of the country? We had no idea but gave it a shot and again, we over-produced and under-produced for some regions but overall, we did well.

Sales went well also. We sold over 19,000 milkweed plugs and at the end of the season distributed 5700 seedlings in bulk lots, mostly to people in northeastern states. Some 4000 plugs remain and most of these will be held over the summer for distribution in the fall to the following states, TX, WI, MI, MN, NY, PA.

We gambled and won! Wow! We wish to thank all of you who purchased these milkweeds – may they flourish and produce many monarchs. We especially wish to thank our partners – The Native Plant Society of Texas, Wild Ones, especially the Tennessee chapter, Nicole Hamilton and the Loudon Wildlife Conservancy for engaging their supporters and encouraging the planting of milkweeds. Special thanks also to Elliott and his excellent staff at AES. Their ability to propagate and grow milkweeds made all of this possible. And, I want to thank Tori Pocius for facilitating all the communications between AES, Monarch Watch and all the customers.

We learned a lot about growing and distributing milkweeds this year. We made some mistakes and have a list of dos and don’ts lined up for next year. So, what should our target be for next year – 30K, 35K or even 40K milkweed plugs? If you are interested in milkweed plugs for you area, contact us at Please consult the Milkweed Market for hard to find milkweeds in your area.

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Monarch Population Status

29 May 2013 | Author: Chip Taylor

Will this be a lean year for monarchs followed by another low overwintering population?

A slow start, a small population and some predictions

Monarchs are off to a slow start this year, with the number moving north in May at an all time low (as indicated by first sightings reported to Journey North). In the following paragraphs I’ll explain why this will be a lean year for monarchs and why the overwintering population in Mexico could be even lower this coming winter than it was in 2012-2013. Predicting whether monarch populations will increase or decrease would seem to be risky or even foolish but, as you will see, there are patterns that support these predictions based on: 1) overwintering numbers; 2) first sightings in the spring (1997-2013); and 3) the impact of temperature on the development of the first generation immature stages and the ability of adult monarchs to move northward to recolonize the breeding areas in the northern states and Canada.

As most of you know, the overwintering monarch population for 2012-2013 was the smallest recorded to date (see our Monarch Population Status article from March 14th). This number defines the upper limit for the number of monarchs returning north in the spring. There are at least two factors that diminish this number – overwintering mortality and mortality as the monarchs migrate through northern Mexico to Texas. Unfortunately, there is no consistent quantitative data on either of these factors. Further, no assessments have been made of the lipid reserves of the monarchs returning to Texas. These reserves are likely to vary from year to year and they probably determine the longevity and reproductive success of the returning females. In spite of the lack of data on these points, the data on overwintering numbers, first sightings and temperature are robust enough to define some patterns and make predictions.

First sightings

The first sightings reported to Journey North have been particularly useful in helping us understand the dynamics of the spring migration. Although first sightings data have a number of limitations, they reveal when and where returning monarchs are seen as they move into the United States and Canada. These sightings also reveal when first generation monarchs moving north and northeast from southern states reach the northern breeding grounds. Even though these data can’t be used quantitatively, they do provide a relative measure of the number of monarchs on the move each spring. Relative to other years (1997-2012) the number of first sightings reported in March and April in Texas this spring was the lowest recorded since 2005 (Table 3). Since more people have been reporting first sightings each year, the low numbers seen this year may be more significant than is suggested by the numbers. Are the low numbers of sightings this spring simply due to the modest number of returning monarchs or is the cooler than normal weather in the mid portion of the country also a factor?

Size of the overwintering population

Although the size of the overwintering monarch population in Mexico is determined by a number of factors, two major drivers of the population (certainly the easiest to document) are habitat area and weather. As you may remember from reading our Blog articles, monarch/milkweed habitat has declined significantly in parallel with the rapid adoption of glyphosate-tolerant corn and soybeans and, since 2006, the rapid expansion of corn and soy acreage to accommodate the production of biofuels (Brower et al, 2011a,b, Pleasants and Oberhauser, 2012 and Taylor, 2012). Monarchs have declined coincident with these habitat losses and the losses are continuing. Monarch numbers will continue to decline unless the collective efforts of citizens, communities, and governments are large enough to offset the annual loss of habitat. While the amount of habitat defines the resource base that monarchs require, weather often determines the extent to which these resources are used in a given year and hence the size of the fall and winter populations.

The impact of weather on the monarch population can be direct and obvious or quite subtle and complicated; especially since the weather conditions in one part of the northern breeding area can differ significantly from those in another. The breeding season for the monarch population extends from March through October (depending on latitude). If we break this season down into three periods, spring (March, April, May), summer (June, July, August), and early fall (September, October) and systematically look at year to year temperature variation for each of these periods, it is apparent that spring conditions are the most variable and most likely to affect the population. And, they do.

Effects of temperature on immature stages and adult monarchs

Before we dive into interpretations of the data, it might be useful to describe the general response of returning monarchs to spring temperatures. Flight and oviposition are both temperature limited. The lower and upper limits for both activities are not well defined but it is safe to say that there is little of either in the spring below 60F or above 90F. Monarchs leave the overwintering sites in Mexico in late February and early March when the late morning temperatures reach the high 60s to low 70s. The conditions are generally clear to mostly sunny at the start of these flights. Presumably, similar conditions have to occur for returning monarchs to move northward into Texas and for first generation monarchs to move into the northern breeding areas. Oviposition can be observed under sunny conditions when the temperatures reach the high 60s. Higher temperatures and reduced wind speeds at ground level appear to facilitate egg-laying. Both flight and egg-laying increase as temperatures increase from these minimal levels through the mid 80s and then begin to decline. At issue is the overall impact of temperature on monarch dispersal, realized fecundity, and longevity.

It is well known that the maturation rates of monarch eggs, larvae, and pupae are temperature dependent. At the highest temperatures, eggs can hatch in 3.5 days; however, at low temperatures egg development can be extended. On the 10th of April 2011, Jackie Goetz observed a newly arrived monarch lay and abundance of eggs on emerging milkweeds in her garden in Overland Park, Kansas. The weather became much colder after the 14th (with an extended cold period from 18-28 April) and those eggs did not hatch until after they were brought indoors on the 29th of April – some 19 days after oviposition. Similar comments could be made about the development of larvae and pupae. Less well-known are the effect of temperatures on adult longevity, egg-laying rates, and dispersal, specifically movement to the north and northeast in the spring.

In the laboratory we extend the longevity and reproductive output of monarchs in our culture by limiting the number of “daylight” hours while keeping the temperatures below 80F. Longer days and higher temperatures can produce large quantities of eggs over a short period but the monarchs die sooner. This outcome is expected. At higher temperatures, metabolic rates are higher and require greater inputs in terms of water and carbohydrates (nectar) and a more rapid conversion of fat body to sugars (trehalose, etc.).

Thus, the response of both the immature stages and adults to lower temperatures is the same. Life is extended in both cases but there is a difference. Extending the duration of development for immatures increases their exposure to predators, parasites, and other incidental causes of death such as heavy rains. However, extending the adult stage probably results in higher reproductive output (realized fecundity) in most cases. So, what should a returning female monarch do? Should it move northward as the temperatures allow, laying eggs along the way or, assuming it has a choice, should it lay most of its eggs in areas where the immature stages will develop most rapidly? As we will see, these data indicate that temperatures above 70F allow the returning monarchs to expand their distribution while periods with temperatures below 70F reduce movement. There are consequences of both moving northward too rapidly and too slowly. The warmer conditions expose the monarchs that have expanded the distribution furthest to the north to late spring storms and cold weather – conditions that reduce egg-laying. Further, the eggs and larvae that are produced by the monarchs on the leading northward edge can be exposed to low, sometimes freezing, temperatures resulting in delayed development and higher mortality rates. On the other hand, cool conditions can result in a delay in the arrival of first generation monarchs in the northern breeding grounds. Both extremes are associated with lower numbers of monarchs during the migration and reductions in the total hectares occupied at the overwintering sites.

Impact of spring temperatures in the South Region

The temperature in the South Region (Texas, Oklahoma, Kansas, Arkansas, Louisiana, Mississippi) in March has a big impact on the number of overwintering monarchs the following winter. The March temperatures for the South Region from 1994-2013 are given in Figure 1. Appended to the mean temperature for each year is a numerical figure indicating the net change in the size of the overwintering population from that of the previous year. Red indicates the population has declined and black indicates an increase in the population from one year to the next. Note that the declines (red numbers) are associated with higher than normal temperatures (7 out of 9 records) for this month while the increases (black numbers) are associated with cooler than normal temperatures or those close to the long-term mean (7 out of 8 records). There would seem to be some predictive value in this simple analysis. Indeed, when I first drew up this figure for the Monarch Biology and Conservation Meeting in Minnesota last June, I put a question mark for the change that might be expected from 2011 to 2012. The high mean temperature for March suggested that the population would decline and indeed it did from 2.89 to 1.19 hectares or a decline of 1.7 hectares. Although a single factor can go a long way in helping us understand what is happening, we can’t ignore the possibility that other factors are involved. If it is really as simple as this summary suggests, we would project that the monarch population will increase from 2012 to 2013 on the basis of the below normal temperatures for March in the South Region in 2013. Unfortunately, this won’t be the case. To understand why I’m making this assertion, I’m going to tell you why this year is both similar to and different from the springs of 1996 and 1997 (there are similarities to other years as well).

The March temperatures for 1996 were the coldest for the period (1994-2013) and the population increased from 12.61 to 20.97 hectares (+8.4 hectares) which is the largest increase yet recorded.* In 1997 the March temperatures were above normal and the population crashed, the worst decline in the record, from a high of 20.97 hectares in 1996 to 5.77 hectares in 1997 (-15.2 hectares). However, neither the increase in the population in 1996 nor the decrease in 1997 was entirely due to March temperatures; April temperatures for each year were strikingly different. While the April temperatures for 1996 were about a degree (F) below normal, those for 1997 were 4.9F below normal (the lowest in this record and the second coldest April from 1895 to present). Further, a blast of cold air with freezing temperatures (some as low as 25F) that extended into Oklahoma and north central Texas during 11-14 April is certain to have delayed development and killed some of the developing larvae and early-arrived adult monarchs in this region. Thus, cold and even freezing temperatures in the South Region in April 1997 likely contributed as much or more to the decline as did the high March temperatures of that year.**

May temperatures also differed substantially between these two years. In 1996 May temperatures were about 4.5 degrees F above normal while those for 1997 were about 3.5 degrees F below normal (also the lowest in this 20 year record). The 1996 conditions would favor rapid movement of the first generation monarchs (which typically begin moving north in the last week of April, with most moving north in May) out of Texas into all of the northern breeding areas (unfortunately, recording first sightings data by Journey North did not start until 1997). However, the colder April and May temperatures in 1997 would be expected to delay the arrival in the north of those that survived the late spring freeze. In fact, the mean arrival date in the north in 1997 was later than for all other years (Figure 14.6, Howard and Davis 2004).

Summer temperatures in the northern breeding areas can also contribute to the size of the overwintering population but the difference between the conditions in June, July, and August did not differ substantially for these two years. The differences in the outcomes were largely due to the conditions from March through May of each year.

Which brings us to why the spring of 2013 is both similar to and different from 1996 and 1997. As you can see from the summary in Table 1, 1996 and 2013 are similar in that both March and April means were colder than usual. These conditions would be expected to slow down development of larvae and reduce the dispersal northward of returning migrants. The May temperatures in 1996 were much higher than those of this year – which will be close to normal. Again, the high temperatures in May of 1996 would facilitate northward movement of first generation monarchs while the more normal May temperatures this year would be expected to neither slow nor accelerate movement northward.

Table 1. Summary of monthly mean temperatures for the South Region.
Deviations from the mean are shown in brackets.

  March April May
1996 49.2 (-4.4) 61.2 (-1.0) 74.7 (+4.5)
1997 56.8 (+3.2) 57.3 (-4.9) 68.2 (-2.2)
2013 51.6 (-2.0) 59.5 (-2.7) ***

***(cold early but near average for the month)

Degree days

We can also use monarch degree days to compare these years. You can find an explanation of degree days in a 2005 article, Monarchs, Cold Summers, Jet Streams, Volcanoes, and More. Monarchs have both low and high temperatures at which development stops. These points are referred to as “developmental zero” with the low point being 52.7F (11.5C) and the high 91.4F (33C) (Zalucki, 1982). The simplest explanation for degree days is as follows: if the mean temperature for a 24-hour period is 1 degree above the developmental zero value, the total degree days for that day is one. If the mean is 20 degrees above developmental zero for a 24 hour period, the total would be 20 degree days and so on. The total number of degree days required from egg to adult is close to 640 Fahrenheit degree days. We have used this estimate to calculate the number of days required to complete development from egg to adult for each of the locations mentioned in Table 2. To compare locations and years we calculated development for eggs laid on the dates indicated. The spread of the dates and locations approximates the estimated dates of arrival of numerous monarchs at particular latitudes (represented by the cities). The developmental times are probably an overestimate since 4th and 5th instar larvae have the capability of increasing their body temperature and reducing overall developmental time by basking in sunlight. Nevertheless, it is the comparison of the years that is important and these figures show that the development times for 2013 bear similarities to both 1996 and 1997 depending on starting date and location (latitude).

Table 2. Approximate number of degree days required from oviposition to emergence for eggs deposited on the March and April dates indicated for each city.

City Latitude Eggs Laid 1996 1997 2003 2013
Corpus Christi, TX 27N 10 Mar 46 40 41 36
Austin, TX 30N 20 Mar 43 50 42 42
Dallas, TX 33N 28 Mar 41 49 39 44
Ardmore, OK 34N 1 Apr 42 50 39 53

Figure 1. March temperatures for the South Region from 1994-2013. Appended to the mean temperature for each year is a numerical figure indicating the net change in the size of the overwintering population from that of the previous year. Red indicates the population has declined and black indicates an increase in the population from one year to the next. Note that the declines (red numbers) are associated with higher than normal temperatures (7 out of 9 records) for this month while the increases (black numbers) are associated with cooler than normal temperatures or those close to the long-term mean (7 out of 8 records). Summer temperatures account for some of the year-to-year changes. Warmer than normal (but not extremely hot (2012)) summers appear to contribute to an increase in the overwintering numbers (e.g., 1995, 1999, 2001, 2003, 2005, 2006, 2007, 2010) (Taylor, 2012 and Barve et al., 2012). It should be noted that this approach only allows us to predict the direction of change and not the amount of the change from one year to the next.

An examination of first sightings

A comparison of the first sightings for 2013 with those summarized in Table 3 would seem to suggest some similarities between 2004 and 2005. A glance at Figure 1 shows that the population declined from 2003 to 2004 by 8.9 hectares (the second steepest decline) while the population for 2005 showed an increase of 3.7 hectares. These observations give rise to a number of questions such as: 1) do the first sightings have any predictive value; 2) aside from warm temperatures in March, were there other factors that contributed to the 2003-2004 decline; and 3) why did the population increase from 2004 to 2005? The answer to the first question is yes, the first sightings do have predictive value but it is the “when and where” of the first sightings that is important rather than the numbers per se. This point should be clearer as we progress through the analysis. The low numbers of first sighting in the spring of 2004 are likely the result of the massive mortality that occurred at the overwintering sites that followed two severe periods of rain and freezing weather in January and February of 2004. The mortality from these storms was not well documented but there are many indications (from the number of recovered tags for example) that the mortality due to these storms was equal to, if not worse, than that of the storm that started on 12 January 2002 during which at least 70% of the monarchs died (Brower, et al 2004). The number of surviving monarchs in 2004 still should have been sufficient to recolonize Texas and produce a large first generation capable of recolonizing the northern breeding areas but that did not happen. The explanation lies in several factors:

1) March temperatures were the third highest of the period (+4.9F) and these were followed by a near-normal April (-0.2F) and a May with above normal temperatures (+1.7F). The March temperatures may have been the most detrimental, and would have been particularly stressful if monarchs that survived the winter storms were in poor condition.

2) The low numbers of returning monarchs, combined with the spring conditions and perhaps other factors, resulted in late arrival of first generation monarchs in the northern breeding areas. Late arrivals (after 1 June) in the summer breeding range are generally associated with population declines from one year to the next. But, there was yet another factor that kept this population from rebounding.

3) The summer of 2004 in the northern breeding areas (East North Central = upper Midwest) was the third coldest since 1895. Cold summers (1992, 2004, 2009) have all been associated with population declines. The conditions in 2005 were almost the opposite – near normal temperatures for March (-0.4F), April (-0.4F), and May (-0.9F) but warmer than normal summer temperatures. The first generation monarchs also arrived late in the northern breeding areas in 2005, although a bit earlier than those in 2004.

So, what does this tell us about what to expect in the fall and winter of 2013? Let’s deal with the number of observations first. Although, the number of first sightings reported in 2013 is similar to those of 2004 and 2005, the number of people reporting first sightings has increased significantly since reporting of first sighting began in 1997 (Howard and Davis 2004). In other words, fewer monarchs have been seen this year by a larger group of observers – suggesting that the number of returning monarchs was lower in 2013 than in 2004 and 2005 (both low returning populations) or even 2010, which saw the lowest overwintering population (1.92 hectares) prior to that of this past winter.

There is a similarity between 2013 and 2004 – the monarchs will arrive late in the northern breeding areas. The mean temperatures for March (-2.0F) and April (-2.7F) were the lowest for these months since 1996 and the April temperatures in particular slowed development of immature stages. May temperatures – which in most of the South Region are near or just below normal – have not appreciably aided northward movement of first generation monarchs. The result of all of these factors is that the arriving number of first generation monarchs will be low and they will arrive late. Even if this projection is true, is there a chance that the population can rebound as it did in 2005? Yes, but the temperatures in nearly all of the northern breeding range will have to be above normal by 2-3F throughout the summer for the population to increase. If the temperatures are normal (and normal summer temperatures are projected by NOAA for the upper Midwest (see the National Weeather Service’s Climate Prediction Center), the overwintering population is likely to be in the range of 1 hectare again this coming winter and could be much lower.

Table 3. First sighting data reported to Journey North (exclusive of areas west of the Rockies and Florida) from 1997-2013. The first sightings reported in March and April represent monarchs returning from Mexico while the majority of sightings reported 1-20 May represent first generation monarchs. Monarchs reported from 21 May through 9 June represent first generation monarchs. First sightings recorded after 9 June are not recorded here for several reasons, these monarchs were probably present in the northern part of the range on 9 June, their numbers are low, and such late arrivers are not likely to contribute substantially to the population relative to those arriving earlier.

Year March April May 1-20 May 21-Jun 9
2013 78 82 42 211
2012 236 137 396 69
2011 148 319 125 273
2010 127 125 157 296
2009 138 209 96 176
2008 124 169 78 227
2007 141 109 118 228
2006 150 192 44 275
2005 74 95 36 151
2004 68 63 60 103
2003 113 86 67 75
2002 197 72 59 164
2001 76 99 199 105
2000 82 109 112 79
1999 54 86 75 111
1998 41 63 106 66
1997 68 109 49 35

The figures below represent first sightings distribution maps for 25 April as recorded by Journey North for the years indicated. The 25 April date was chosen since sightings up to this date are likely to include only monarchs returning from Mexico. The maps were selected to represent a range of March and April conditions from the coldest (2013) to the warmest (2012) spring. The mean temperatures for each month and the deviations from normal are given in the lower right corner of each map.

* A moderate drought extended through most of Texas in March and April of 1996.
**The first sightings data appears to show that monarchs move “around” the jet stream to the northeast when it dips into the central part of the continent in the spring. This movement may account for the number of monarchs recorded per hour during the fall migration at Cape May, NJ in 1997. In contrast to the Midwest, where the migration was relatively low, the monarch monitoring at Cape May in 1997 yielded the 5th highest count per hour in the 21year history of that program.


I wish to thank Elizabeth Howard of Journey North for allowing me to modify and incorporate first sighting maps in this article. Janis Lentz graciously helped with the weather data, summarized the first sightings data, and calculated the projected degree days for eggs laid on specific dates at each location. Jim Lovett and Ann Ryan once again added their excellent editing touches to the text and compensated for my limited abilities to provide the proper formatting by doing things the right way.


Brower, L.P., Kust, D.R., Rendon-Salinas, E., Serrano, E.G., Kust, K.R., Miller, J., Fernandez del Rey, C. & K. Pape, K. (2004) Catastrophic winter storm mortality of monarch butterflies in Mexico in January 2002. Monarch Butterfly Biology and Conservation (ed. by K.M. Oberhauser and M. Solensky), pp. 151-166. Cornell University Press, Ithaca, New York.

Brower, L.P., Taylor, O.R. & Williams, E.H. (2011b) Response to Davis: choosing relevant evidence to assess monarch population trends. Insect Conservation and Diversity. doi: 10.1111/ j.1752-4598.2011.00176.x

Brower, L.P., Taylor, O.R., Williams, E.H., Slayback, D.A., Zu- bieta, R.R. & Ramirez, M.I. (2011a) Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk? Insect Conservation and Diversity. doi: 10.1111/j.1752- 4598.2011.00142.x.

Howard, E. and A. K. Davis (2004) Documenting the spring movements of monarch butterflies with Journey North, a citizen science program. Monarch Butterfly Biology and Conservation (ed. by K.M. Oberhauser and M. Solensky), pp. 105-114. Cornell University Press, Ithaca, New York.

Pleasants, J. M. and K.S. Oberhauser (2012) Milkweed loss in agricultural fields because of herbicide use: effect on the monarch butterfly population. Insect Conservation and Diversity (2012) doi: 10.1111/j.1752-4598.

Barve, V., O.R. Taylor, J. Lentz and E. Howard (2012) Monarch population Dynamics: The relationship of temperature to patterns of recolonization by monarchs returning from Mexico. Monarch Biology and Conservation Meeting: Minnesota 2012 (Presentation by Vijay Barve)

Taylor, O. R. (2012) Conservation and restoration of monarch butterfly habitats. Monarch Biology and Conservation Meeting: Minnesota 2012 (Presentation by O. R. Taylor)

Zalucki, M.P. (1982) Temperature and the rate of development in two species of Danaus, D. plexippus and D. chrysippus. J. Aust. Entomol. 21:241-246.

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