Journey North: Monarch Butterfly Fall, 2004

Monarch Butterfly Migration Update: October 29, 2004

Today’s Update Includes

Las primeras mariposas monarca han llegado!
The First Monarchs Have Arrived!
Now Crossing the Narrow Finish Line
Like Finding a Needle in a Haystack?
Try This! Challenge Question #12

Las primeras mariposas monarca han llegado!
The first monarchs have arrived! Here’s the news from Estela Romero, who lives in the sanctuary region in the small town of Angangeuo:

Germán Medina drives tourists to see the monarchs in this truck. He also coordinates the Symbolic Migration in Mexico.

“I received from Germán Medina the first news from the first Monarchs arriving to Angangueo. Germán took a walk Sunday, October 24 to ‘El Cerrito.’ This is one of the first places the Monarchs stay for some days before finally reaching their last destinations, the Sierra Chincua and El Rosario sanctuaries. Well, he saw 13 (thirteen) trees not totally covered with butterflies, but with bunches hanging on the branches of each one. He counted the trees. He immediately came after noon time and told me.

“This afternoon (October 26), I talked to a couple of women from El Rosario. They were coming from 'Las Papas,' a meadow at the Sierra Chincua sanctuary. They go there for picking mushrooms which they sell downtown. They assured me that both in El Rosario and Sierra Chincua, the Monarchs are already there. ‘A lot of them have arrived already,’ said the women. 'Actually, today we saw them while we were picking up mushrooms at noontime, at El Llano de los Conejos' (a meadow inside the El Rosario sanctuary).

“The weather here is wonderful, very sunny days, blue sky, (20-25 Centigrade). Angangueo is, I feel, in general, eager for this season. But we are aware indeed of the big damage made to the forests and aware also of what this could bring in the future for the whole region.”

Now Crossing the Narrow Finish Line
This winter, the monarchs in Mexico will cluster together on only 10-12 volcanic mountains. They'll form large colonies containing tens of millions of butterflies. Typically, some 80% of the butterflies will concentrate in only four colonies.

The monarchs find these mountaintops each year as if by magic. Imagine a marathon, with monarchs crossing the finish line each day by the thousands. Amazingly, the "finish line" they must hit is very, very narrow---only 73 miles wide.

After crossing half a continent, the monarchs must find a finish line only 73 miles wide. The over-wintering sites, shown on map as red triangles, are within this narrow region.


The monarchs fly up to 2,500 miles to spent the winter in these mountains.

Find the finish line on the map above: The western-most end is the colony named Mil Cumbres (-100.8 W) and the eastern-most side is the Nevado de Toluca (-99.7 W), where the Palamas, Pierra Merrada and Oxtotilpan colonies are found. 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 a 73 mile-wide window to find the overwintering sites!

Like Finding a Needle in a Haystack?

The monarchs come from the area in red, measuring over 9 million square kilometers.

This map shows the HUGE area in North America across which monarchs move on their way to the sanctuaries in Mexico.

The monarch breeding grounds, shown in red, measure over 9 million square kilometers!

In contrast, the over-wintering sites are a tiny speck on the planet. They are clustered in a region that measures only 800 kilometers square.

The monarch over-wintering grounds, shown in yellow, measure only 800 kilometers square.

This means that the monarchs find an area that 11,000 times smaller than the area the migration crosses. Finding a needle in a haystack almost sounds easy in comparison! The monarchs certainly seem to know where they?re going, don?t they?

Try This! Challenge Question #12
Just how small is the over-wintering region? Let's look at this in local terms to help form a picture.

Look closely at the map above showing the 12 sites. Notice the scale of the map and the distance between the 12 sites. Find a dozen towns near you that fit in a similar area, 800 kilometers square. Outline the region on a large map of North America. Have you visited these towns? Would people traveling across of North America have trouble finding your region?

Next look at the width of the area. Consider how narrow the monarch's 73 mile-wide finish line is:

Challenge Question #12
?What's the name of a town that's 73 miles from your home town? In your answer, share your thoughts after doing this mapping activity."

How to Respond to Today's Challenge Question
1. Address an e-mail message to: jn-challenge-monarch@learner.org
2. In the Subject Line of the message write: Challenge Question #12
3. In the body of the message, answer the question above.

The FINAL Monarch Migration Update Will Be Posted on November 5, 2004.