Monarch Butterfly Migration Update: February 16, 2000
Today's Report Includes:
Field Notes from the Monarch Sanctuaries
For those of us waiting for the monarch migration to begin, this week's news from Eligio Garcia signals some exciting
changes. After clustering tightly together during the coldest months in Mexico (December - January), the monarch
colonies have begun to break up and the butterflies are beginning to descend the mountains. During Eligio's February
10 visit to the Sierra Chincua sanctuary, the monarchs were clustering in only 168 trees. Where there had been
350 butterfly trees all winter, now only about half as many remained. The rest of the butterflies have moved down
into the Zapatero Canyon, tens of meters beneath the main colony. At the other sanctuaries Eligo visited last week,
he saw that the colonies were also breaking down for the first time this season. Eligio noticed another change.
This change was in the butterflies themselves. Here are his words:
"Las mariposas empiezan a madurar sus organos sexuales y comienzan a aparearse." (Link to Online
Challenge Question #4
"How have the monarchs begun to change? Why is this important?"
(To respond to this question, please follow
the instructions below.)
Fecha, Altura, Temperatura
Discussion of Challenge Question #1
When Eligio visits the sanctuaries each week, he measures and records 9 things. Because he sends his data in Spanish,
we want to make sure you can read it! Thanks to Mrs. Callaway's fourth grade class in Chesterton, Indiana for sending
their translations. "Were we close?" they wanted to know. Yes! The fourth graders came up with six correct
answers. Here are all nine:
Fecha (Date), Numero de Arboles (Number of Trees), Altura (Altitude), Temperatura (Temperature), Hora (Hour),
Ciel (Sky, meaning cloud cover), Viento (Wind), Exposicion (Exposure), Pendiente (Slope).
By observing and recording this information every week, Eligio is learning about the habitat the monarchs choose,
and how it changes at different times of the year. He wants to know for example, How high in the mountains do the
colonies form? How steep is the land? How much sunlight does it receive? Which direction does it face? (exposure)
Is it protected from cold north winds? Is it near water?
All of the factors Eligio measures help define monarch habitat. In these mountains, the "microclimate"
is very different depending on slight differences in location. So the location of the colony can mean life or death
to the monarchs during storms and cold winter temperatures. (See Dr. Bill Calvert's story below.)
Understanding monarch habitat use is extremely important for another reason. Scientists want to make sure the proper
land is protected for the monarchs--at all times of year. In fact they are learning that, when the monarchs move
down the mountain as they are right now, they are often moving out of the sanctuary--and into land that is not
protected. This is because, when the sanctuary land was designated back in 1986, scientists only knew where monarchs
clustered during cold winter months. Scientists are now learning that as the season warms, the monarchs' needs
seem to change. They move down the mountains along the watersheds--and these critical watersheds are not protected.
Instead the land is in private ownership.
Here is the data Eligio has collected at Sierra Chincua since the monarchs arrived in November. Count the number
of trees the butterflies were using each week that Eligio visited. Notice how the colony builds up in the fall
and declines in the spring:
Weather Report from Escuela Pedro Ascencio
At 10,000 feet elevation, where the monarchs spend the winter, over-night temperatures can drop to freezing. All
of Mexico is not warm and sunny! Cold temperatures, wind, rain, and even snow can affect the entire population
of monarchs resting in this region. Students at Pedro Ascencio school live beside the Sierra Chincua sanctuary.
Monarchs often fly silently over the school yard, to and from the sanctuary.
Since school began last September, Pedro Ascencio students have been maintaining a small weather station. This
will help us understand how the climate and weather change during the monarchs' over-wintering season. "Los
ninos y yo continuamos tomando y enviando con mucho gusto los datos meteorologicos en la localidad de Garatachea,"
writes Professor Gilberto Salazar. Each day the students are recording the day's high and overnight low temperatures.
They are also noting if there was rain or snow, and whether dew ("rocio") or frost ("helado")
is present in the morning.
Challenge Question #5
"Why might information about rain, snow, dew and frost be important to measure? How might these things affect
(To respond to this question, please follow
the instructions below.)
Life in Sanctuary Region: Meet Noemi de Jesus
Noemi de Jesus is a student at Escuela Pedro Ascencio. She lives on the hill behind the school, and walks through
the forest to school every morning. A Symbolic Monarch that was made by Jerita in Starr, South Carolina flew to
Mexico. It landed near the Sierra Chincua sanctuary--and in Noemi's hands. You can see her pictured here with Jerita's
Enjoy your visit to Noemi's home! We hope these first-person accounts will portray the personal side of monarch
conservation, as seen through the eyes of the children and families who live in the region. Watch for a new story
each week, in both English and Spanish.
Why So Few Monarchs at Chincua This Year?
Discussion of Challenge Question #2
As reported last week, this winter there were only about 350 trees filled with monarchs in the Sierra Chincua sanctuary.
This compares to 1,700 trees last year. We asked: "How does the size of this year's monarch population at
Sierra Chincua compare to last year's? What conclusions can you draw from Eligio's monitoring data? What possible
explanations might explain the change?"
Miss Bailey's students in Vero Beach, FL (firstname.lastname@example.org) wrote: "We figured out that this year's
monarch population at Sierra Chicuna is only 20% of last year's. Spencer thinks that there may have been more predation
this year. Not as many monarchs survived the winter. Steven thinks that some of the monarchs may have died while
traveling to Mexico. Matthew thinks that some monarchs didn't migrate to Mexico because the winter up north was
warmer than usual."
As these students calculated, the population at the Sierra Chincua sanctuary is much lower than last year--a drop
of almost 80%. The students thought of many possible reasons why the monarch numbers could be down. But what can
be concluded from Eligio's data? We asked monarch biologist Dr. Bill Calvert for his reaction:
"Population data from one colony can be misleading. ALL the major colonies must be measured to determine population
"Therefore, a low population at one sanctuary--the Sierra Chincua--may not mean that the whole population
is down. It may simply mean that some other colony has received the bulk of the butterflies this year. Eligio Garcia
has measured all of the major colonies this winter. When the data from all of the colonies is before us, we can
estimate the population size."
Introducing Monarch Biologist Dr. Bill Calvert
Dr. Calvert is familiar to most Journey North readers. He was one of the first biologists to study the monarchs
in their over-wintering habitat--and certainly the one who spent the most time with the butterflies. From 1976-1982,
he and his coworkers traveled to Mexico several times each season averaging nearly two months each year in the
sanctuaries. The time in residence with the monarchs varied, but he was most often there for several weeks at the
beginning of the season (November or early December) and there for longer periods at the end (February and March).
He actually camped in the mountains, often within a few hundred meters from the colonies, and experienced the same
cold, wet conditions the monarchs endure.
"It was so cold in the colony one January (1981) that nearly half of the butterflies froze to death. I saw
the incredible importance of the forest as a protective blanket protecting the surviving butterflies against the
cold. The ones that survived were lucky in being in relatively warm pockets within the forest (we are talking minus
3 degrees instead of minus 5) or they were the ones buried in the snow thereby insulated from the extreme cold."
Dr. Calvert will be in the sanctuary region for the next three weeks. He's offered to send news for these weekly
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: email@example.com
2. In the Subject Line of your message write: Challenge Question #4 (or #5)
3. In the body of the EACH message, answer ONE of the questions above.
The Next Monarch Migration Update Will Be Posted on February 23, 2000.
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