Mead’s Milkweed and Monarchs

From time to time the question arises as to whether monarchs can and do use all species of milkweeds in the genus Asclepias or whether there are some that are too toxic or have so much latex that larvae are unable to feed properly and die. There could even be some species that lack the chemistry that allows the larvae to even start feeding. Stated another way, it seems possible that some milkweeds might have become as unpalatable to monarchs as they have to other herbivores. It would be valuable to know the answer to this question but we will have to gather more data on what species females chose to lay eggs upon and whether larvae successfully feed and reach the adult stage on a number of species.

There are 72 species of native milkweeds in the genus Asclepias found in the United States. Monarchs use about 30 of these species as host plants with some regularity. Little is known however about the use of many species, particularly the more than 20 that have limited distributions including a number that are rare and endangered. I live in a county (Douglas County, KS) in which 13 species of Asclepias have been recorded. I know locations for 12 of these within the county and have found monarch eggs and larvae on 9 of the 12 species. Two of the three species without eggs or larvae, A. stenophylla (slim leaf milkweed) and A. amplexicaulis (clasping milkweed), are relatively uncommon in the prairie meadows I’ve visited and I’ve always assumed that the lack of evidence of use by monarchs was just a matter of numbers with monarchs simply laying eggs on the most abundant and apparent species. I also knew that monarchs use A. amplexicaulis as a host in other areas.

I reached a similar conclusion with regard to the third species, the rare and endangered Mead’s milkweed, A. meadii. I’ve actually encountered many more plants of this species than of the previous two but again no monarch larvae on any of these plants. Mead’s milkweed is a poor choice as a host, most plants have 6 rather small leaves, the nodding flower-head, if present, is relatively large but overall it seems unlikely that there is enough foliage on a Mead’s milkweed for a single larvae to complete its development. I know better than to speculate that monarch females are smart enough to avoid plants with insufficient foliage but still I had looked at a lot of these plants (hundreds) over the years with nary an egg or larva sighted. So it was with some surprise that I learned that two biologists, Steve Roels (a graduate student at the University of Kansas) and Dr. Retha Meier (Saint Louis University), who study Mead’s milkweed had observed monarch larvae on these plants. I asked Dr. Meier to write up her observations. Here is her report along with two images. Steve Roels provided a third image.

Mead’s Milkweed and Monarchs
By Dr. Retha Meier

Dr. Peter Bernhardt and I began the first season of a three-year study on the pollination of the threatened, Mead’s milkweed (Asclepias meadii) in May 2010. The population we observed grows in a prairie near Garnett, Kansas. Mead’s milkweed is easily overlooked, even where it is common. Each year a plant produces a single, thin, graceful stem that ends in an umbel made up of 5-14 nodding, greenish-colored flowers. Nectar gushes from the horns of these flowers and measures more than 50% dissolved sugar in some flowers. We also discovered that Mead’s milkweed flowers emit an unusually pleasant and spicy fragrance similar to oil of cloves. Nectar and odor must have attracted the monarchs to the dangling blossoms because we watched on numerous occasions as these insects positioned themselves upside-down to drink. While searching for more Mead’s in this diverse prairie we often found it was easier to just follow monarchs to previously unmarked stems in bloom.

One morning while Dr. Bernhardt was measuring floral nectar he discovered that some monarchs were doing something more than drinking. They were laying eggs. He found small stages of the larvae consuming the flowers including the nectar-rich horns. Only one caterpillar was found per umbel but even an early instar, less than 5 mm in length, was capable of doing a considerable amount of damage as it began feeding on the flowers. As flower consumption continued, the small instar grew into a much larger caterpillar that eventually eliminated all the flowers on the umbel. Here we have an example of a much-loved insect spending a most important part of its life-cycle on an increasingly endangered plant. Monarchs didn’t pollinate Mead’s milkweed on the Kansas prairie. Capture and release procedures showed that their mouth-parts and legs were free of the distinctive pollen packets (pollinaria) of their wildflower host. That honor, we’ve learned, belongs to a few, chunky native bees like the Anthophora abrupta.

Steve Roels added the following observations:

Retha’s observations about monarchs on the Welda are similar to my own. Interestingly, monarch herbivory was extremely common on the Welda this year (I believe I saw caterpillars on 10-15 of the 50 stems I was monitoring) but monarchs have been much less frequent on the KU field station Mead’s the last two years. I’m not sure if the difference is due to different butterfly population levels or that plants are easier to find on the Welda because the vegetation is shorter and less dense, making plants easier to find. When caterpillars are present, they can do a tremendous amount of damage, sometimes completely stripping the stem of leaves and buds. They seem to prefer the buds, or perhaps eggs are more frequently oviposited there, and generally the caterpillars work their way from the top of the plant downwards. However, sometimes I have seen caterpillars present one day and then they are gone a few days later, perhaps shuffling off to find a more suitable host plant or getting picked off by some predator. Monarchs did reduce the Welda Mead’s population’s reproductive output to some extent this year but I suspect Cycnia inopinatus is more of a widespread problem for Mead’s.

As far as I know, no one has done any work on the chemical profile of Mead’s as compared to other milkweeds, which could be relevant for a number of herbivores. I considered pursuing this route, but I have plenty of projects as it is. I do wonder if it has lower levels of toxic compounds than other species because deer herbivory at the field station is extremely high in the early spring and I have never seen any deer damage to A. syriaca and only very rarely, if at all, on A. viridis. Some other milkweeds do suffer from the deer including a dense 8’x4′ patch of A. purpurascens that was completely razed last year at the field station.

Additional references for Mead’s milkweed:
http://plants.usda.gov/java/profile?symbol=ASME
http://www.fws.gov/midwest/endangered/plants/pdf/meads-fnl-rp.pdf

Mexico Travel Advisory

We have received a number of inquiries from people who want to know if it is safe to travel to Mexico, specifically to visit the monarch overwintering colonies near Angangueo (El Rosario and Sierra Chincua), Zitacuaro (Cerro Pelon), and Valle de Bravo (Herrada). Most people know of the conflicts among the drug cartels and between the army and these cartels. Most of the violence associated with these conflicts occurs in the Mexican cities and states bordering the United States but some occurs in the states of Michoacan and Mexico, where the overwintering monarchs reside, and in scattered locations along the Pacific coast. It used to be safe to drive into Mexico from the United States and I’ve done it at least 30 times without incident. However, driving into Mexico is no longer safe and should not be attempted. While most of the violence involves cartel members attacking each other and fighting with federal troops, a number of students and visitors to northern Mexico have been killed.

Tours to the monarch overwintering sites are still accepting applications and if you would like to visit Mexico this winter to see the monarchs, we advise you to join one of the tours rather than renting a car. Foreign tourists have not been targeted and traveling in groups should be safer than traveling alone.

Five groups we are aware of (there may be others) that are still booking tours appear below. If you go on one of these tours, please give us a report about your impression of the number and condition of the monarchs and let us know of your experience in general.

U. S. Department of State Travel Warning
The U. S. Department of State’s Bureau of Consular Affairs (travel.state.gov/) provides a lot of good information for those traveling abroad, including a current “Travel Warnings” page. So what exactly is a travel warning?

“Travel Warnings are issued when long-term, protracted conditions that make a country dangerous or unstable lead the State Department to recommend that Americans avoid or consider the risk of travel to that country. A Travel Warning is also issued when the U.S. Government’s ability to assist American citizens is constrained due to the closure of an embassy or consulate or because of a drawdown of its staff.”

On September 10, 2010 Mexico was added to this list which, as of this writing, includes 30 other countries. Please see the Mexico Travel Warning page for complete information.

Plant Fundraisers

In case you haven’t gone through the text on our Bring Back The Monarchs website, one of the things we are trying to facilitate is helping anyone who holds plant fundraisers (nature centers, zoos, native plant societies, schools, etc.) acquire wholesale plants, particularly milkweeds, that can be sold at these events.

We recently received an email from a teacher who wants our help acquiring plants for a spring plant fundraiser that is going to be held at her school. We are contacting nurseries all over the country who grow milkweeds to see what is available. We are careful to identify to the sources of seeds used for plugs to be sure that plugs used for restoration were grown from seeds from the same ecological region.

We need more letters like the one below. Our mission in this project is to help these types of fundraising projects and to promote the planting of milkweeds in both gardens and in areas that can be restored.

If you know of anyone planning a plant fundraiser in 2011, please let them know of our goals and willingness to help them with these projects. Thank You!

Greetings:

I am a teacher at USD 504 Service Valley Charter Academy in Oswego, Kansas.

I attended the spring open house at KU last year and purchased a lot of plants to put in our school registered Monarch Waystation that we created.

I read on the Monarch Watch facebook page about the Bring Back The Monarchs program and our school is very interested in setting up a plant fund raiser for Southeast Kansas. Our school received charter funds 3 years ago. Our charter is built around the use of agriculture to reach our students and this would fit very well into our program. We have a greenhouse on school grounds and would like information on ordering plants wholesale through Monarch Watch.

We have had community individuals stop by the school asking about purchasing milkweed and I am very excited about the possibility of making plants available to our region of the state.

I share the passion of Monarch Watch and this will give my classroom and school a chance to increase awareness in our corner of Kansas.

Thanks for your assistance.

Theresa

Monarch Population Status

If you have been following the news about monarch populations over the last 8 months, you know that the 2009 overwintering monarch population in Mexico covered a forest area of only 1.92 hectares. This figure represents an all time low for overwintering monarchs and is well below the long-term average of 7.44 hectares (1994-2010). We worried about these low numbers because of the possibility that a devastating storm could drive the population even lower. And then it happened…a storm of the worst possible dimensions hit the overwintering area starting on 2 February. Fifteen inches of rain fell over a four day period. Large hail hit some areas and snow and freezing temperatures were reported subsequently during another period of precipitation. The consequences were devastating for the residents of the monarch overwintering area. Accounts of the flooding and landslides can be found in the Mexico category of the Monarch Watch Blog.

Attempts to find out how the monarchs fared following these winter storms were unsatisfactory. No measurements were made of the numbers of monarchs killed by the storms. Accounts by visitors to the colonies after the storms suggested that substantial numbers of monarchs died during these events. Reports from reliable observers suggested that as much as 80% of the butterflies died at some colonies while others suggested moderate mortality at one large colony of perhaps 20%. Overall we estimated that at least 50% of the monarchs died during the winter months, recognizing that this value could have been low.

Our next concern was the number of butterflies coming north in late February and March. Would the number of surviving butterflies be sufficient to establish a first generation in Texas and the South large enough to lead to a recolonization of the northern breeding areas and a recovery of the population?

Fortunately, the conditions encountered by the monarchs that reached Texas were favorable. Rainfall over the previous 6 months signaled an end to the long drought and produced an abundance of milkweed. The fire ants were down due to the drought and temperatures were lower than normal which seems to favor production of first generation monarchs. The result, in spite of the low number of returning monarchs, was a substantial first generation. These butterflies colonized much of the northern breeding area from late April to mid-June; however, not all areas were well colonized.

The numbers of monarchs reaching the northeastern area (New England and New York) seemed to be well below average, leading to the expectation that the fall migration in this region will be low. Rainfall and temperatures in the central area (Ohio, Indiana, Tennessee, etc.) were not ideal as monarchs arrived from the south and the fall population in this region is likely to be below average except for those areas receiving butterflies from eastern Ontario, which reported many arriving monarchs in May and early June. Based on the numbers of arriving monarchs and the abundance of eggs and larvae found by observers, the fall migration in the east north central region (eastern Dakotas to Michigan) should be above average – assuming that temperatures do not reach the 100s before the end of August.

In summary, it appears that the monarchs are making a modest recovery and I expect the overwintering population will measure close to 3 hectares.

2009 Season Tag Recoveries

We have been receiving lots of questions about when the 2009 season tag recoveries will be posted. We do not have a large number of them at this point due to the fact that we did not make our annual trek to the monarch overwintering area in Mexico. As you may know, the heart of the monarch overwintering area was devastated by heavy rainfall, hail, landslides, and flooding earlier this year – you can read about this disaster of extraordinary proportions right here at

monarchwatch.org/blog/category/mexico/

We have posted a preliminary list of 2009 season tag recoveries (from Canada, the U.S., and Mexico) and will be adding to it as additional reports come in. Rest assured, we will eventually have all of the recovery data out of Mexico (it is likely to be a large number of tags due to the storms) and will add them to our tag recovery database as soon as possible.

Stay tuned!

Two-way Monarch Migration Map

With the assistance of noted graphic artist Paul Mirocha of Tucson, Arizona we have created a two-way monarch migration map:

Our goal was to produce a comprehensive map representing both the fall and spring migrations both east and west of the Rocky Mountains. To the extent possible, the map is based on data. Nevertheless, our knowledge of the distribution and abundance of monarchs in some seasons is lacking for certain areas of the country. In these cases, our interpretations are based on what monarchs are doing in surrounding areas.

There are two question marks on the map; one represents the possibility that some monarchs move north through the Sierra Madre Occidental into California and Arizona and the other the uncertainty concerning the spring movement of monarchs out of Florida. Although it is clear that monarchs build up in Florida each spring, it is not clear whether the offspring of the spring generation moves northward along the east coast. Tagging has failed to resolve this issue. In fact, the origin of the spring monarchs in Florida is not absolutely clear. Do they originate from populations in extreme southern Florida that have matured on naturalized* and cultivated Asclepias curassavica, from monarchs returning from overwintering sites in the mountains of Cuba, or butterflies that have returned from overwintering in Mexico, or some combination of these? The Mexico connection is particularly puzzling since it is unclear why spring migrants, that are generally on a N/NE track, would take an easterly or even slightly southeasterly track to reach central Florida. My hope is that these question marks will inspire a resolution of these issues.

Similarly, you will notice that the corn belt is roughly outlined on the map. Historically the corn belt has been an area of high monarch reproduction, a point emphasized by the isotope study conducted in 1996 (1) that showed roughly 50% of the monarchs that reached the Mexican overwintering sites originated in the corn belt and the subsequent finding published in 2000 (2) showing that corn and soybean fields were the most productive breeding habitat for monarchs in the Midwest. Subsequent to these studies (but beginning in 1997) Roundup Ready soybean varieties, typically used in rotation with corn, were introduced to the American farmer as a cost and energy effective means of weed control. Unfortunately, the widespread planting of these genetically modified seeds has eliminated milkweed from at least 100 million acres of row crops. Clearly, there is less milkweed/monarch habitat available in the corn belt than there was in the past but has this reduced monarch reproduction in these areas or have monarchs simply shifted their reproduction to common milkweed at other disturbed sites? Habitats for monarchs are becoming increasingly fragmented and there are more and more areas where monarchs are unable to reproduce due to the lack of milkweed and nectar sources. We need to know how monarchs respond to these changes to mitigate habitat losses.

Lastly, the map is not perfect in that it doesn’t represent all that we know about monarchs. For example, there is an area (roughly 36 to 40N) of overlap of reproduction by butterflies returning from Mexico in April with a region of continuous summer reproduction. We tried to represent this overlap on the map but failed. The map became cluttered and confusing. Similarly, there are three migratory generations (did you know that?): the fall migration; the first generation offspring of the returning fall migrants that move north from late April to mid June; and an as yet poorly defined migration southward in late July and early August, about a month before the fall migration, that recolonizes the southern Midwest and south. This third migration, which I’ve given the unfortunate name of the “pre-migration migration” (and it truly is a migration), is not represented on the map nor is the late season reproduction in the south that sometimes results from this flight southward.

Please note that this map is copyrighted and may only be used with permission from Monarch Watch. We plan to create a poster based on this map for display in classrooms, nature centers, at events, etc. – this will be available via the Monarch Watch Shop.

References

1. Wassenaar, L.I. and Hobson, K.A. 1998. Natal origins of migratory monarch butterflies at wintering colonies in Mexico: new isotopic evidence. Proc. Nat’l Acad. Sci. U.S.A., 95:15436-15439.

2. 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. Temporal and spatial overlap between monarch larvae and corn pollen. Proc. Natl. Acad. Sci. USA 2001 98: 11913-11918.

For more on Roundup Ready Crops and Milkweeds see:

Roundup-Ready Crops and Resistant Weeds (Monarch Watch article)

Effects of Transgenic Crops on Milkweeds (Monarch Watch article)

Farmers Cope With Roundup-Resistant Weeds (New York Times article)

*Asclepias curassavica has been recorded in 17 counties in Florida.

Addendum

The above map resembles, but differs in many details from, maps published by Lincoln Brower in 1995. The Brower maps were not consulted in the production of this map.

The two-way map is based on my 18 years of experience following the monarch migration in great detail through the monarch tagging program, reports to Dplex-L and Journey North and from hundreds of emails and phone calls. The inclusions, omissions, and errors are mine.

The Brower maps appear in two publications:

Brower, L. P. 1995. Understanding and misunderstanding the migration of the monarch butterfly (Nymphalidae) in North America: 1857-1995. Journal of the Lepidopterists’ Society 49:304-385.

Brower, L. P. 1996. Monarch butterfly orientation: missing pieces of a magnificent puzzle. Journal of experimental biology 199:93-103.

Monarch Population Status

Abstract
Monarchs are off to a good start and the population should increase modestly from now until the fall migration, assuming normal temperatures for the remainder of the breeding season. While an increase is likely, we still don’t have a good estimate of the size of the returning monarch population. If the population of females returning from Mexico has been low, the number of first generation monarchs heading north through May and the first half of June will also be low relative to other years and will limit population growth through the rest of the season. First sightings for March and April, as recorded by Journey North, show a population more restricted temporarily and spatially than recorded for any of the previous 10 years. The size of the overwintering population last year was 1.92 hectares (“Monarch Population Status” January 2010) and, with a modest increase this summer, the population might get back to this number. If the conditions for the rest of the summer are highly favorable, a winter population of 4 hectares is possible but that doesn’t seem likely at this point. In any case, the winter population of 2010 is certain to be below the long-term average of 7.44 hectares.

Analysis
I spend a lot of time fretting over the status of the monarch population and I’m always searching for factors or data that will help me understand the past as a way of predicting the future trends in monarch numbers. Since the status report of 2 March, I’ve been pouring over the first sightings records reported on the Journey North website. Like many of you I’ve looked at the Journey North first sightings maps from time to time and occasionally at the individual records but I’ve haven’t attempted to analyze these data.

I’ve looked at the data in some detail over the last several weeks and there are some neat patterns that I will explain in the future. My specific task at this time was to see if the first sightings data contained any clues as to the size of the returning population. I was concerned about this issue since there were no quantitative estimates of the numbers of monarchs that survived the winter storms. To answer this question I looked at the total number of first sightings reported in years with low and high numbers of returning monarchs. Unfortunately, the numbers of first sightings are not related to population size. There are several problems with working with the raw numbers. The numbers of first sightings has increased over the years as the network of monarch observers has increased making it difficult to compare one year with another. There are other problems such as trying to account for the density of observers, which is higher in and around cities compared to the surrounding countryside. In addition, it is difficult to determine if weather conditions such as cold fronts, and rainy periods in particular, affect the number of observations. And, publicity could play a role in the number of observations reported. In years when the population is low, monarchs tend to get a lot of publicity and general awareness of the low numbers might lead to an increase in the reported sightings. Further, since the number of observations does not correlate with the numbers of returning monarchs, does this mean that there is a finite number of people who will report what they see? Given all of these issues with the data, is there still a way it can be used? The short answer is yes, but caution is required. One thing we can do is look for patterns in the data and use proportions of monarchs seen in a give place or by a given date to compare one year with another.

I’m not going to dive deeply into the data but I will show you briefly how this year compares with others – and this returning population has been most unique. One way to look at the data is to ask how many of the first sightings reported in March* come from Texas and how many are reported from areas outside of TX. On average about 78% of the March first sightings are from Texas, this year an astonishing 96.8% of the first sighting were from sites within Texas. April was also distinct in this regard, since 8 of 22 (36.4%) observations from 22-30 April** were reported from Texas. In 7 of the last eleven years no Texas sightings have been reported during this period and the remaining years had 2, 2 and 1 Texas sightings. Overall, combining March and April sightings, 73% were from Texas, more than 20% higher than the long-term average. The data clearly shows that monarchs were limited to Texas this spring more than in any of the previous 10 years. What does this mean? Was the dispersal of monarchs limited this spring because of the lower than average temperatures or because the population is low or some combination of both? The answer is probably the latter; a combination of low numbers of returning monarchs and lower temperatures. Further analysis is needed.

As I pointed out in the addendum to the last status report, low numbers of returning monarchs could limit the amount of increase in the population we might expect in the breeding season even under the most favorable conditions. Assuming the returning numbers have been low, and there is no evidence to the contrary, what might we expect for the fall migration and the overwintering population in Mexico. Actually, the report based on the first sightings is not all doom and gloom. The conditions for growth in the monarch population in Texas have been exceptionally favorable the last two months. The temperatures have been moderate and due to adequate soil moisture, the milkweeds and nectar sources have been abundant. In addition, the fire ants have been scarce having not recovered from the prolonged drought of last year. So, small population or not, the monarchs should be off to a good start. Whether the population will just replace itself this year, increase above last year’s numbers or decline once again will be determined by 1) the number of first generation monarchs that come N/NE out of Texas over the next 6 weeks and, of course, 2) the weather conditions throughout the northern breeding range over the remainder of the summer. The May and June first sightings reported to Journey North do not appear to be as informative about future trends in the population as the March and April records but, we will be following them intensely just the same.

*All sightings from Florida and from west of the Rockies have been excluded from this analysis.

**April records used in this analysis were inclusive of 1-21April since an examination of the individual reports show than an increasing number of the sightings after the 21st of April clearly involve first generation monarchs.

PollinatorLIVE: A Distance Learning Adventure

Dr. Chip Taylor, Director of Monarch Watch, will participate in a webcast on May 12 from 1:15 to 2:30 p.m. ET and discuss tagging monarchs, the current status of the population, Monarch Waystations and more.

Dr. Taylor is participating in the webcast as part of PollinatorLIVE: A Distance Learning Adventure. For more information and to register, go to pollinatorlive.pwnet.org. PollinatorLIVE is continuing last year’s distance learning adventure that focused on monarch butterflies. This year’s FREE distance learning adventure will feature pollinators, citizen science projects, and gardening.

Update: If you missed the live webcast you can now check it out online at

pollinatorlive.pwnet.org/webcasts/webstream.php

Monarch Watch Spring Open House & Plant Fundraiser

It’s that time of year again!

Monarch Watch Spring Open House & Plant Fundraiser
Saturday, May 8th 2010 8am-3pm
KU’s West Campus, Lawrence, KS

This free public event usually attracts 500-1000 visitors and we expect the same this time around.

Nearly 4,000 butterfly plants (both annuals and perennials), including seedlings of several milkweed species, will be available (modest contributions are suggested). A list of available plants is posted at the bottom of the Open House page.

We will also provide refreshments, lots of show & tell, videos and games for children, tours of our garden and lab space, iChat videoconferencing demonstrations, and, of course, monarch butterflies!

You may have heard about our “Monarchs In Space” project but you can learn more about this program on Saturday and see the actual monarchs that traveled from Monarch Watch to the International Space Station and back to Monarch Watch, a mere 40 million miles – that’s quite a migration!

We’d love to see you here so mark your calendars! If you can’t make it in person, be sure to check us out online – we plan to post photos and broadcast some LIVE video throughout the day.

Complete details, including a map and directions, are available online at

monarchwatch.org/openhouse

If you have any questions please feel free to drop us a line anytime!

Grants Available to Create Monarch Waystations

On the 12th of May I will be part of the Pollinator Live webcast at the National Zoo. I will provide more details on how to connect with this broadcast in the near future but you can get some details from the Pollinator Live website.

My role will be to talk about monarchs and to take everyone to “butterfly school” much as I do when we have our tagging day at the Baker Wetlands in Lawrence each September. However, we will touch on other pollinators as well and at some point while trying to explain insect vision you may see me pretend to be a praying mantis.

But, the real point of this communication is to tell you that Kristy Liercke, one of the organizers of this event, wanted me tell you that there are small grants available for people who wish to start Monarch Waystations / pollinator gardens at schools.

The maximum grant amount is $500 and the deadline to apply is December 3, 2010.

In her words she asked me to

“spread the word that the project has grant money for gardens. So if you have people needing a little money to start Monarch Waystations, please have them apply.”

Complete details (including additional grant opportunities) are available at:
Project Learning Tree GreenWorks! Pollinator Garden Grants