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Monarch Butterfly Migration Update: March 7, 2001

Today's Report Includes:

Field Notes from Mexico
Snow Hits the Monarch Region
On this week's visit to Sierra Chincua, Eligio Garcia observed winds gusts up to 77 km/h (47 mph). He did not count number of trees filled with monarchs this week, and says many butterflies had been grounded by the storm.

Dr. Calvert Reports: How Does Snow Affect Butterflies?

March 4, 2001
Snow in all parts! The climb up the Nevada de Toluca from the city of Toluca was painfully slow due very heavy traffic. Everybody and his brother was out for an adventure in the snow. Snow is infrequent here in Central Mexico. The day was crystal clear and the snow was melting fast so everyone had to hurry before it disappeared. As we climbed toward the pass we saw snowmen of every variety on the hoods, tops and trucks of cars. The favorites were dogs, or I should say "snowdogs" if there is such a word. Dogs wore sunglasses, kerchiefs around their necks, and often times hats of different styles.

The storm that brought the snow had occurred on Friday night and Saturday morning. In Mexico City it rained hard and winds blew hard, sweeping the city clean of pollution so that the volcanos Popocatepeti and Iztaccihuati were clearly visible in a splendid mantel of white. The Nevada de Toluca was also snow white.

Along the road there was much evidence of remaining snow and especially plant carnage. The weight of wet snow and strong winds had broken tens of thousands of limbs. It had snapped off and uprooted trees. At the Herrada colony the trail we normally take to view the butterflies drinking water was almost impassable due to downed trees and branches. There were no butterflies to be seen. We can only speculate what happened in the butterfly colonies. Tomorrow we will know, when we visit Chincua and El Rosario.

After a snowstorm, I'd expect that most butterflies would survive, even many of those stuck in the snow. Miraculously, once the snow melts, I've seen them warm up and finally move off. They might even be buried for up to a week!

However, the year of the devastating snow storm (1981) we were monitoring mortality in the Chincua colony and documented tremendous mortality. Review the data we collected (see link below). Then compare the safety of the monarchs that were on the ground to those that were clustered on a tree bough.

Until next week,
Bill Calvert

Where Would You Rather Be?
Based on Dr. Calvert's data above, what could you conclude about the safety of the two positions within the colony during a snow storm?

Challenge Question #11
"Do you think monarchs are safer on the ground or in a bough cluster? Give real data to support your answer. (Dr. Calvert suggests, 'You may want to convert the raw data to percent of sample to get a better idea about what is going on!')"

(To respond to this question, please follow the instructions below.)

Monarch's Forest Like an Umbrella and a Blanket
Dr. Lincoln Brower has studied the monarchs in their wintering sanctuaries for over 20 years. Whenever he describes the monarchs' winter habitat, he uses this analogy:

"The forest serves as an umbrella
and a blanket for the monarchs."

Read about the oyamel forest habitat in the two articles below. Since you're already familiar with blankets and umbrellas, you can apply your knowledge to a question about monarch habitat.

You may be surprised how helpful analogies can be when answering any challenging question. Try this one!

Challenge Question #12
"How does the oyamel forest serve as an umbrella and a blanket for the monarchs?"

(To respond to this question, please follow the instructions below.)

How is a Hot Dog Like a Shoe? Thinking by Analogy
The world of science and invention is filled with examples of analogous thinking. Here's a fun activity you can do to practice thinking by analogy:

Two Geographic Clues Led Brower and Calvert to the Monarchs

Dr. Urquhart told the world of his discovery of the monarch over-wintering sites in the August, 1976 issue of National Geographic. However, he concealed their actual location--even from Dr. Lincoln Brower, the world's eminent monarch scientist. Here Dr. Bill Calvert tells about the clues the two scientists found in the National Geographic article that led them to the sites. Their tale of discovery illustrates just how unique the oyamel forest ecosystem is: By knowing only that the butterflies were in state of Michoacan and at an elevation of 10,000 feet they were able to pick out the spot on a map--and travel there!

Life in the Sanctuary Region
What's in a Family Name?
What would your name be if you lived in Mexico? Karina Romero de Avila walks you through the steps to find out:

Important: Please Report Winter Monarch Sightings Now
We need your help before the monarchs arrive from Mexico. In order to track the migration accurately, we need to know where monarchs may have remained all winter.

This map shows where people have already reported monarchs.

Please Report Your Winter Monarch Sightings NOW!

People assume the spring migratory monarchs are all coming up from Mexico but we really don't know the importance of the Gulf Coast over-wintering population.

How to Respond to Today's Monarch Challenge Questions:

IMPORTANT: Answer only ONE question in each e-mail message.

1. Address an e-mail message to:
2. In the Subject Line of your message write: Challenge Question #11 (or #12).
3. In the body of the EACH message, answer ONE of the questions above.

The Next Monarch Migration Update Will Be Posted on March 14, 2001

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