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Contents:
1) Welcome!
2) Adopt-a-Classroom Trip Un-Cancelled ;-)
4) Overwintering Biology: How Monarchs Get Through the Winter
5) 10,000 Nature Books and Audio/Video Titles!
7) Why the 2001 Season Summary is So Late
8) How to Unsubscribe from this Update
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1) Welcome to Monarch Watch's Update List!
You are receiving this email because you have provided Monarch Watch with your email address at some point and expressed interest in receiving updates from us. If you do not wish to receive these periodic (probably monthly) email updates or feel that you were subscribed in error, please see the unsubscribe information at the end of this message.
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Monarch Watch (http://www.MonarchWatch.org) is a not-for-profit educational outreach program based at the University of Kansas. We run a Monarch tagging program and offer Monarch Rearing Kits, Monarch Tagging Kits, and other educational/promotional materials that allow you to actively experience the monarch life cycle and its spectacular fall migration.If you have any questions, please feel free to contact us anytime!
Your friends at Monarch Watch
http://www.MonarchWatch.org
monarch@ku.edu
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2) Adopt-a-Classroom Trip Un-Cancelled ;-)
Last month we cancelled the annual January Adopt-a-Classroom trip to Mexico because of insufficient funds. However, since then we have decided to make the trip and are determined to come up with the necessary funding. We are somewhat a victim of our own success and poor foresight. When we started the program we obtained a modest amount of supplies from schools and it was an easy matter to get these materials to Mexico. Now that the program has grown to the point that tons of materials are involved, the expenses are substantial - about $9000/trip; however, we failed to alert all our contributors that donations of funds, raised through aluminum can drives, etc., were every bit as important as the donated supplies themselves, hence, the shortfall. If all goes as planned, we will deliver the contributed materials to 30+ schools in the vicinity of the Monarch Reserve in early March. If you would like to contribute to this effort, checks can be sent to:
Monarch Watch
University of Kansas
1200 Sunnyside Avenue
Lawrence, KS 66045
Thank you for your continued support!
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3) Status of the Population - by Chip Taylor
Good news! I was wrong. In the premigration newsletter distributed in August, I predicted that the overwintering population would probably be no greater than 5 hectares when all colonies were measured. As the migration progressed, and reports of poor production of monarchs continued to come in from numerous areas, I downsized the prospective overwintering population each month to a mere 3 hectares. The colonies are still being measured but it would appear that my doom and gloom scenario is wrong. Preliminary indications are that, although the population is not as large as last year’s 9.35 hectares, it is much larger than the all time low of 2.83 hectares measured in 2000. Hopefully, we will have more specific information to report next month.
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4) Overwintering Biology: How Monarchs Get Through the Winter - by Chip Taylor
Many scientists have puzzled over the question of how monarchs get through the winter, that is, how they manage to sustain themselves without feeding and while clustered in the oyamel fir trees in the mountains in Mexico. There is substantial and somewhat confusing literature on this topic. The simple answer is that monarchs metabolize the fats stored in their abdomens, converting these fats to sources of energy, carbon dioxide, and water. But this is only part of the story, we have to know where the fats come from, how much fat is needed, whether the use of the fat is related to environmental conditions, whether there are differences between the sexes, the amount of fat required by butterflies moving north in the spring, etc. In the following summary, I will blend my understanding of the facts with interpretations and outright conjecture.
Insect Metabolism
Monarchs obtain energy from two sources, the foliage of the host plants as larvae and nectar from flowers as adults. A portion of the energy assimilated by the larva carries over into the adult stage, principally as lipids stored in what is known as the fat body - loose sheets of fat tissue in the abdomen. Adults visit flowers for water, carbohydrates, and amino acids. Most butterfly flowers are 80-90% water and 10-20% dissolved solids - mostly sugars and amino acids. The role of amino acids in adult nutrition is not yet clear but they could have a role in maintaining the adults and by providing the building blocks needed for sperm and egg production. Amino acids tend to be higher for flowers visited predominantly by butterflies than for those adapted for bee pollination suggesting that these flowers have coevolved with butterflies.
Energy is stored in two ways in the adult butterfly, as glycogen and as lipids. Glycogen is synthesized from glucose or amino acids. Trehalose, the principal blood sugar in insects, is produced either from glycogen or directly from glucose. In the presence of the enzyme trehalase, trehalose breaks down to glucose, providing energy for flight and other energy-demanding functions. Lipids consist primarily of triglycerides, mostly palmitic and oleic acids, stored in the fat body and diglycerides in the hemolymph (blood). The lipids are synthesized from carbohydrates and amino acids. The later suggests another reason for butterflies to visit amino acid rich flowers. The diglycerides in the hemolymph are derived from hydrolysis of the triglycerides in the fat body. The diglycerides combine with proteins and form lipoproteins before entering the hemolymph. Energy is derived from the progressive oxidation of the diglycerides to acetyl-coenzyme A which enters the citric acid cycle yielding energy, carbon dioxide, and water. Lipid metabolism predominates in diapausing insects because lipids contain more potential energy and yield more metabolic water per unit weight than carbohydrates. The relative dependence of monarchs on lipid vs carbohydrate metabolism may vary with their reproductive status.
Metabolic Rates of Reproductive and Non-Reproductive Monarchs
One of the monarchs’ remarkable features is its ability to respond to changes in the physical conditions in a manner that reduces or elevates metabolic rates and reproduction. When a monarch first emerges from a pupa, the abdomen contains a substantial fat body. If the temperatures are high (90s) at emergence and for the subsequent 48 hours, juvenile hormones produced by the corpora alata initiate a process that leads to egg formation in females and spermatogenesis in males. At these high temperatures, and high rates of metabolism, some monarchs will mate at the end of the second day. If the temperatures are lower, but still within the range of summer temperatures, mating may not be initiated until day five. However, if the temperatures are even lower (e.g., 45-65F) such as those experienced by late summer (late August) monarchs in northern states, the monarchs do not mate. Rather, they begin to add to their fat body by converting the sugars and amino acids from the nectar obtained from flowers to lipids (primarily triglycerides) that are stored in the fat body in the abdomen. The metabolic rates of reproductive monarchs are substantially higher than for non-reproductives. The non-reproductives are said to be in reproductive diapause, an arrested state of development in which production of juvenile hormones that trigger reproduction is minimal. The biochemical chain of events that leads to a reduction of metabolic rates and rapid lipid uptake in these diapausing monarchs is not clear to me but once the butterflies enter this condition, they appear to adopt behaviors that maintain their lower metabolic rates. In addition, they express behaviors, a large number in fact, that facilitate the orientation, navigation and flight habits that allow them to migrate to Mexico and to return to the southern portion of the breeding habitat in the spring.
There is evidence that host plant quality and physical conditions experienced by larvae and pupae predispose newly emerged adults to enter diapause but it is also clear that diapause and lipid uptake can be induced in adults reared as larvae under summer conditions. Diapause is easily broken in monarchs by simply raising temperatures under indoor conditions; duration of the photoperiod does not appear to be a factor.
Lipid Acquisition
The distribution of lipids in monarchs throughout the migratory season and along the migratory pathway from the north to Mexico suggests that lipids are acquired, and lipid mass increases, during the migration. Samples of monarchs taken during the migration at one location show that lipid content is highest during the peak of the migration and lowest among stragglers. This observation leads to the speculation that many of the butterflies in the last third of the migration are at a disadvantage during the migration since they have minimal stores. Further, if they make it to Mexico, they are unlikely to survive the winter unless substantial food reserves have been acquired during the migration. Since nectar availability declines as the fall season progresses, increasing fat reserves late in the season may be difficult. The stragglers tend to be smaller than early and mid-stream monarchs which may also put them at a disadvantage. Monarchs lacking a full complement of fat take on water as ballast. The water serves to distribute the weight posteriorly so that the butterfly has an equal anterior/posterior weight distribution near the center of lift. If the abdomen is too light, the butterfly would tend to pitch forward during flight. The water is displaced as the butterflies acquire nectar and convert it to lipids in the fat body. The highest mean weights are obtained for monarchs newly arrived at the overwintering sites. This seems to indicate that lipids are acquired during the migration, especially as the monarchs traverse the last 500 miles through the mountains in Mexico. However, it may also be that many monarchs with low reserves simply do not survive the migration, thereby shifting the mean to a higher value. The distributions of monarch sizes, masses and lipid stores need to be examined for the entire course of the migration. Even though the mean lipid content is higher for newly arrived monarchs, many monarchs arrive at the overwintering sites with little or no reserves. Their prospects for survival appear to be low.
Survival, Lipid Mass, and Metabolism
Estimates of lipid mass vary among authors but can average as high as 126 mg or 42% of the dry weight of the butterfly. As the winter progresses, the lipids are depleted reaching 59 mg or 27% of the dry weight. Thus, at the end of the overwintering season 53% of the fat body has been utilized yet 47% remains to sustain the migration north and the protein synthesis required for reproduction. As the butterflies move north they feed extensively on available flowers reducing their dependence on stored lipids to meet immediate metabolic needs. The minimum amount of lipids required for a monarch to overwinter successfully has been estimated to be 100 mg but this may be high since it was based on less refined estimates of respiratory rates than are now available.
Since the smallest individuals have the highest mass-specific metabolic rates and males have higher metabolic rates than females, the group surviving best should be those females with the highest lipid content. In other words, in terms of differential survival, based on size and metabolism alone, we would expect the smallest males to die first followed by small females, and then average sized males and females with the larger males and females surviving best. These predictions have not been tested under field conditions.
Sources of Water
Much has been made of the effect of forest thinning on the temperatures within the forest and the potential for thinning to reduce the capacity of the forest to retain heat. Under extreme conditions, such as those seen last winter and at the most degraded sites such as San Andres, loss of heat and increased exposure of the butterflies to rain, snow and wind probably contributes to mortality of the overwintering butterflies. Yet, there is another confounding observation. Often the colonies form around an opening in the forest. One of the colonies at Cerro Pelon is almost circular in form around a hole in the forest. If they need the protection, why do they often cluster on the edge of clearings? There could be several reasons. The clearing allows sun to penetrate and reach the clustered butterflies facilitating activity. The clearing itself heats up during the daytime allowing the butterflies to catch rising air but it also cools faster at night and this could be important for another reason – water. The monarchs need water. When they are feeding on flowers, much of their water comes from nectar. In the absence of water from nectar, overwintering monarchs visit seeps along streams but the most important source of water may be from condensation or dew that forms on the vegetation and on the clustered butterflies themselves. Thus, the surface of the adjacent butterflies and the substrate may serve as a water source when the temperature reaches the dew point allowing condensation to form on the cluster. Since the overnight temperatures within a gap in the forest are lower than in the surrounding forest, the dew point is likely to be reached more frequently within the gap and the adjacent trees than in the forest. In other words, there may be more water available to the monarchs around the edges of gaps than within the forest. Monarchs do not cluster near gaps because they "know" the physics of dew formation; rather, they must be selecting these sites on the basis of other physical parameters. Late in the season (February) the dynamics change as water becomes available in the form of nectar from the many Asteraceae that begin to bloom within and adjacent to the farm fields down-slope from the colonies.
Water Loss and Metabolic Costs Associated with Different Colony Sites and Seasons
Monarchs lose water through respiration and respiratory losses should be greatest when temperatures and metabolic rates are higher and when relative humidity is lower. Relative humidity decreases through the winter season, and temperatures rise as the winter progresses leading to greater water stress in the monarchs as the season advances. The dew point is reached less frequently due to the lower humidity and higher overnight temperatures and many of the springs and seeps begin to dry up. Daytime temperatures being higher late in the season permit more flight and the colonies frequently move slowly down the hillsides by reclustering after each activity period on the portion of the colony that receives the last sun of the day (e.g., to the SW). How much this movement is the result of the search for water is not clear. The seasonal history of a colony can often be traced up-slope by backtracking the trail of dead butterflies left behind as the colony moves downhill. Because tree density, exposure, relative humidity, etc. varies among colony sites, we would expect water loss/stress and metabolic rates, and therefore lipid loss, to vary among sites and this is indeed the case. It is also likely that it varies from year to year with extremely dry years (such as during severe El Nino events) being the most stressful.
The Value of Activity at the Colony Sites
If monarchs can sustain themselves by metabolizing fats during the winter and given that flowering in the area is insufficient to provide a source of nectar and therefore energy or the butterflies, why do the monarchs take flight whenever the sun and temperature permits? One of the most impressive sights at the colonies are the massive flights of monarchs over the trees, up and down the slopes at El Rosario, and laterally along the edge of the escarpment at Chincua. These flights usually occur under sunny conditions when the winds are slight to moderate and the temperatures are in the 60s. The simple answer is that the butterflies are seeking water but this probably isn’t the case for most of the butterflies. The majority of the gliding and soaring butterflies don’t appear to be seeking anything more than flight itself. Why? Well, I’d fly too if I could but it may be that flight has an important metabolic function. Before flight, the butterflies need to elevate their body temperature by muscular thermogenesis (shivering) and by using their wings and body to capture incident radiation from the sun. Flight allows the butterflies to attain slightly higher thoracic and abdominal temperatures and therefore higher metabolic rates and this may facilitate absorption of wastes from the blood by the malpighian tubules, elimination of these wastes, and the conversion of lipids in the fat body to available diglycerides and trehalose from glycogen in the hemolymph. In other words, by taking flight the butterflies may be preparing themselves for additional periods of inactivity. Since soaring and gliding predominate during these flights, the energetic costs should be minimal.
Starvation
Many of the monarchs found dead at the overwintering sites have depleted fat bodies and appear to have "starved" to death. However, some of the monarchs seem to be in good condition, begging the question - can monarchs "starve" even if they are full of fat? If the amount of water produced as lipids are metabolized is less than the amount needed to sustain physiological functions, including the continued breakdown of fats, clustered butterflies at low temperatures in dry environments without access to water in the form of condensation or dew, could become dehydrated and die. This scenario might explain the large number of DWACs (butterflies "dead without a cause") found beneath the clusters in the oyamel firs each winter in Mexico. These butterflies are often in prime condition and a "full" of lipids. It seems possible that these deaths are due to insufficient water to maintain catabolism of the lipids in the fat body. DWACs may not be confined to Mexico since modest numbers of apparently healthy butterflies are occasionally found dead under temporary overnight clusters during the migration in states as far north as Minnesota.
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5) 10,000 Nature Books and Audio/Video Titles!
Did you know that Gulliver’s Gift Shop has more than 10,000 nature book and AV titles? We added over 7,000 new titles last October and now just about any nature book you could want you can find in Gulliver’s Gift Shop.
We have more than 775 field guides from butterflies and moths to seashore life - there are guides for novice and expert, kids and adults. We carry 184 butterfly titles! We have more than 2,500 titles for kids and the same number of gardening titles. Our books run from $1 and up, so you should be able to find something in your field of interest and price range.
The next time you need any nature book please check Gulliver’s Gift Shop. Each purchase benefits Monarch Watch.
**FOR THE NEXT 30 DAYS ONLY** Every time you buy more than $10 of books from Gulliver’s Gift Shop we’ll SEND YOU "ENJOYING BUTTERFLIES MORE" FOR FREE.
"Enjoying Butterflies More" is a wonderful booklet that helps identify some of our most widespread butterflies, tells you how to attract them to your habitat, and provides some fascinating information on butterfly biology. It is written by Jeffery Glassberg, President of the North American Butterfly Association and produced by Bird Watcher’s Digest and has a retail value $3.99. It’s yours FREE and will be added to your package when you purchase $10 or more in books.
Visit Gulliver's Gift Shop at http://shop.monarchwatch.org
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Last month we indicated our intention to purchase at least 1,100 tags during our trip to Mexico. We believe purchasing this many tags is possible because we anticipate that local residents are still in possession of about 1,000 tags found last year after the storm; additionally, we expect that there will be about 300 recoveries of butterflies tagged this past fall. Thanks to those who have contributed to this fund, we now have sufficient funds to purchase approximately 740 tags. We will have to try to cover any additional tags from our operating budget; therefore, we could still use your help with the Tag Recovery Fund. If you would like to contribute to this fund, please send your checks to:
Monarch Watch
University of Kansas
1200 Sunnyside Avenue
Lawrence, KS 66045
Thank you!
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7) Why the 2001 Season Summary is So Late
We apologize for the lateness of the Season Summary. It is our intention to write the text for this publication from February to April each year and to have the copy ready for the printer in May. We couldn’t keep to this schedule last year. By April it became clear that, due to a variety of circumstances, Monarch Watch was $30,000 in the red. Not only did we not have the money to publish the Season Summary but our very existence was threatened. We had no recourse but to put all projects aside, including the Season Summary, while we attempted to restructure and to get our finances back in the black. Our restructuring has involved the development of a partnership with Home Earth to handle our orders and increase our customer base, a reduction of staff from three full-time people to two, and a reduction of expenditures. These changes have been difficult but the finances, while not rosy, are coming around and we don’t anticipate the same end of year financial woes this coming spring.
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