As promised, Bill Calvert and colleagues have sent a report about their recent trip to Mexico to estimate the size of this winter's monarch population. Before reading the report, try to imagine how YOU would go about counting all the monarch butterflies that are wintering in Mexico!
To: Journey North From: Bill Calvert, Austin, Texas RE: POPULATION SIZE OF MONARCH COLONIES IN MEXICO
We have been in Mexico working with the Wildlife Conservation Society to obtain an estimation of the 1994/95 Monarch population size. The total number of butterflies is probably about 60,000,000 this year; somewhat less than we originally predicted but nonetheless a sizable population.
The estimates are the simplest possible. In 1986 we did a mark & recapture study at one of the sites in January. On the basis of that study we estimated 13,000,000 monarch per hectare. Since then, off and on, we have measured the total surface area of all the colonies in Mexico. Simple multiplication gives an estimate, albeit crude, of the total monarch population for that year. There are certain factors we must take into account. Packing is the most dense in January and early February. Therefore we must measure the colonies in that time period.
Our intention is to work up the old data this spring. I have not yet done so. My impression is that this year's population is as large as ever. But a better statement will be forth coming. The reliability of the estimates is off course dependent on the assumptions made. I'm sure our reviewers will have much to say about these assumptions.
We found 13 colonies in Mexico most of which were small. No colony was greater than a hectare in area, although the sum of the areas at Chincua was 2.32 ha. (There are still about 9 areas. Some areas such as Chincua and Pelon have more than one colony. This is why 13 colonies are listed.)
The agency protecting the butterflies (Profefa) seems to be in place and effective. Profefa is a government agency. They are the environmental police charged with the protection of the Monarch colonies. We were under their surveillance each time we entered a colony to measure it.
Colonies in the state of Mexico seemed especially well protected. In Michoacan much lumbering had been done before Profefa became active. So although it appeared that some habitat was destroyed, it very likely occurred before Profefa's became effective. One colony in particular was in poor shape. The trees were second growth no more than 40' high. The butterflies were draping the low trees in dense curtains all the way to and spilling onto the ground. The sight was quite spectacular and beautiful. But since there was hardly any high overstory to radiate heat downward at night, the butterflies were poorly protected from the cold weather. High mortality was evident in the population of butterflies on the ground.
The Wildlife Conservation Society is currently funding an effort to determine what normal monarch population levels are and a microclimatic study to try to discern what are the microclimatic requirement of overwintering Monarchs.
Regards,
Bill Calvert ======================================================
CHALLENGE QUESTIONS
How Many is Sixty Million? It's hard to imagine such a large number, so let's translate butterflies into people and see what we get:
1) Begin with the population of your state or province. Now start adding! First add the number of people in your neighboring state or province. Next add the population of as many states or provinces as you can until you reach 60 million.
Make a list and send it to us at: jnorth@informns.k12.mn.us
2) What do 13,000,000 butterflies per hectare look like? First find out how large a hectare is. If there are 13,000,000 butterflies in a hectare, how many would there be in an area the size of your classroom? How many monarchs would there be for each person in your class?
Send your answers to: jnorth@informns.k12.mn.us
Last Week's CHALLENGE QUESTION
What is Microclimate?
From NEW YORK: Buffalo Science Museum Magnet school Buffalo, N.Y. mwisniew@gateway.drew.buffalo.k12.ny.us
You sent me the question: What is a microclimate? Well, I got the answer. It is a small climate area, with few changes in the weather.
Mark Wisniewski, 4th grade
From NEW YORK: East Hills School Roslyn, NY K12ROBZJ@vaxc.hofstra.edu
This is Mrs. Berger's class's definition for microclimate: microclimate- The climate of a small area, as of confined spaces such as caves, houses, etc.
From MINNESOTA: Katherine Curren School Hopkins, MN sue_dewit@hopkins.k12.mn.us
I'm Anne Wilkinson from Katherine Curren school in Hopkins. I found that microclimate means the climate of a small area, as of confinedspaces such as caves or houses. I am serving as a "resident scientist of monarch" for the second graders in my building.
Classroom Activity: A Microclimate of Major Importance
1) After reading today's two scientific reports from Mexico, discuss the specific microclimatic conditions that are found at the monarchs' winter sanctuaries. Why are temperature and moisture so important to the monarchs? What kinds of human activities might affect these conditions?
2) Go outside and see if you can identify local microclimatic conditions. Climatic conditions in local areas can differ from general climatic conditions due to nearby geographical features (mountains, oceans, lakes), biological features (forests, prairies), and man-made features (buildings, parking lots, croplands, cities). These areas have a different "microclimate" due to the varying amounts of sunlight, wind and moisture they receive.
3) Measure and compare temperatures in areas that have different microclimatic conditions. (For example: areas with southern vs. northern exposure to the sun, areas that are wooded, grassy or paved.) Keep temperature records for a few weeks and graph the changes over time. Compare the growth rate or flowering dates of dandelions or other common plants in each area.
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