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Monarch Migration Update: October 27, 1999
Today's Report Includes:
- The First Monarchs Have Reached the Sanctuaries!
- Challenge Question #18
- Millions Now Traveling the Route Through Mexico to the Sanctuaries
- Finding the Narrow Finish Line
- Challenge Question #19
- The FINAL Fall Monarch Update Will be Posted on November 17
- Link toThis Week's Migration Data
The First Monarchs Have Reached the Sanctuaries!
From Angangueo, student Luis Fernando Romero reports the news we've all been waiting for:
21 & 22 octubre
"El jueves y el viernes fui a visitar el santuario 'El Rosario'. Hay muchas mariposas, y hay algunos arboles llenos tambien!"
Angangueo, Michoacan (19.62 N, -100.30 W)
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Luis Fernando Romero |
Map of Sanctuary Region |
Challenge Question #18
"When did the monarchs arrive, and what does Fernando Romero say about them?"
(To respond to this question, please follow the instructions
below.)
Millions Now Traveling the Route Through Mexico to the Sanctuaries
Also on Friday, just a short distance to the northwest, Senor
Juan Pablo Martinez-Soriano reported that the monarchs began to arrive in great numbers in Irapuato, Guanajuato
(20.66N, -101.35W) on the 22nd. He wrote on Tuesday, October 26:"Hundreds of monarchs are flying over Irapuato, Guanajuato. The Michoacan sanctuaries are three-hour drive from here. Irapuato is right at the centre of Mexico. Place your finger right at the heart of the country (Mexico) and there it is. The sanctuaries are located 160 km to the southeast. The last two days have been very windy and the monarchs are not advancing anymore from here. I see them flying from the west but as soon as they reach the line of trees, they stop. The trees are tall (30 feet) and protect them from the wind so the monarchs prefer to stay behind them. (Wind blowing from NE.) The numbers are increasing with time and at this point the scene is really a breathtaking one. It is impossible to calculate the numbers... It really looks like one of the colonies at the sanctuaries. I know now that there are other places (trees) in different areas of the city that are being chosen by monarchs. One of chosen ones is a secondary school...the kids are nuts ! ... a incredible celebration is going on." (jpms@irapuato.ira.cinvestav.mx)
About one hundred miles to the north of the sanctuaries in Celaya, Guanajuato (25.67N, -100.32W), senor Edmundo Durell also sighted the first monarchs on Friday, October 22 and said he was "talking with the locals, who said they had not seen Monarchs until today." (edmundo.durell@mx.york.com)
Finding the Narrow Finish Line: Challenge Question #19
Millions upon millions of butterflies are now traveling across Mexico to the sanctuary region. Dr. Bill Calvert describes the migration pathway on which they're traveling. As you read his remarks, look at a physical map of Mexico and see if you can find the Sierra Madre Oriental Mountains.
"At the latitude of the southern tip of Texas, the monarchs' flight path is only about 8% as wide as it was when they started from their breeding grounds in the North," says Calvert. "This funneling is due to the Gulf of Mexico and Mexico's Sierra Madre Oriental (the Rocky Mountain's extension into Mexico). Enormous numbers of monarchs travel through the mountainous areas in the Mexican states of Coahuila and Nuevo Leon and further south, because these geographic features compress the monarchs' flight-path. When they reach deep, central Mexico they get thicker and thicker and are easier to find as they are concentrated by the Sierra Madre Oriental along which they fly.
"These mountains seem to focus the migration, and direct it towards the overwintering sites located in the Transvolcanic Belt of central Mexico (19.62 N, -100.30 W). The Sierra Madre Oriental forms a great elongated massif that stands in the path of the easterly winds that predominate at this time of year. In short, as easterly winds blow, the butterflies get a 'lift' from these winds. The air rises over the east-facing mountain slopes of the multiple ranges of the Sierra Madre. When the butterflies fly through the inner montane valleys of the Sierra Madres, this rising air makes flight much easier. During late afternoon, after a day when no or few butterflies have been seen, they often quite suddenly "fall out" of the sky and begin to nectar or to form their evening roosts.
"Amazingly, the sanctuary area the monarchs have to hit is very, very narrow. The western-most side is at Mil Cumbres (-100.8 W) and the eastern-most side is the Nevado de Toluca (-99.7 W). This is an area only is 1.1 degrees wide, in longitude. This means that, assuming that monarchs cannot 'home' and correct the consequences of a miss, those migrants flying in from the north must strike the Transvolcanic Belt somewhere within this 1.1 degree window to find the overwintering sites."
Challenge Question #19
"Based on the measurements Dr. Calvert provides above, how wide is the monarchs' finish line"?
(To respond to this question, please follow the instructions
below.)
This winter, the entire eastern population of monarch butterflies in Mexico will cluster together on only 10 or
11 volcanic mountains, in large colonies estimated to contain millions of individuals. Significantly, an estimated
80% of the butterflies each year in only four core colonies. (All of the colonies are in Mexico's Transvolcanic
Belt, and most of these colonies are spread along an arc from the western face of the volcano "Nevado de Toluca"
to the northeastern extreme of the state of Michoacan. The four core sites are located in the center of the arc,
near Angangueo.)
The FINAL Fall Update Will be Posted on November 17
FINAL Monarch Update Directly From the Sanctuaries
Now that the first monarchs have reached the end of the long trail, this is our final "migration" update of the fall season. However, watch for a final posting from the sanctuary region later this month, when the Symbolic Monarchs are being delivered.
Summary of This Fall's Challenge Questions
We have included discussions of many of this fall's questions, but some have not been addressed. Therefore, we will gather the answers and post them as part of the FINAL monarch update in November.
How to Respond to Today's Monarch Challenge Questions
IMPORTANT: Please answer ONLY ONE question in each e-mail message!
1. Address an e-mail message to: jn-challenge-monarch@learner.org
2. In the Subject Line of your message write: Challenge Question #18 (or #19).
3. In the body of EACH message, answer ONE of the questions above.
The FINAL Monarch Update Will be Posted on November 17, 1999.
Copyright 1999 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form
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