Monarch Butterfly Update: March 17, 1998
Today's Report Includes:
Field Report From Mexico
Dr. Calvert is now back home in Texas where he'll watch for the monarchs' arrival. If you're in Mexico or Texas, we hope you're ready to report your FIRST migrating monarch of the season. Remember to note the condition of the butterfly's wings so you can be reasonably sure you're reporting a migrating monarch, rather than one that over-wintered in your area.
To: Journey North
From: Dr. Bill Calvert
March 16, 1998
"This colony was the Rosario "bud colony". It was the lower part of the Rosario colony that had budded off from the main colony, which occupied a site in the same drainage, but at a higher elevation. Each day more butterflies left the upper (original) colony and joined the bud colony. At this point in time (March 11), it was hard to tell whether the bud colony or the main colony had more butterflies. The bud colony was stopped from descending to even lower elevations by fields and pastures that came all the way up to 3000 m elevation. Earlier in the year the butterfly colony was located above the Llano del Conejo at 3240 m elevation. Monarch colonies always descend the mountain during the course of the monarch's 5 month tenure. This descent accelerates during late February and March when the combination of intense sunshine and lack of clouds and moisture in the air warms up the ambient considerably. The descent is almost always associated with a particular arroyo or drainage.
"At Rosario they usually follow the drainage called Arroyo Los Conejos. However, this year they used another drainage about 1.5 km to the northwest of Los Conejos. This small drainage is not named on the local topographic map, but is called (inappropriately) the Rio Grande by the locals. When we were there (well into the dry season), there was only a little water flowing in it. In contrast, at Chincua, the monarchs first formed one of their colonies at 3100 m and descended to 2800 m by mid-March. At Chincua they had plenty of dense forest with a good supply of water to shield them from the intense tropical sun and associated warmth.
"The lack of forest at the field edge did not stop them entirely however. During the day butterflies poured out of the bud colony and over the ridge at the little community, La Salud, towards Angangueo. These butterflies are undoubtedly part of the return migration to the United States and Canada. Each day tens of thousands pass through the town of Angangueo. They are all going in the same direction - northward. Back towards Rosario, many thousands are taking nectar from flowering plants, especially eupatorium and scenecios along the road to Angangueo. Many of
these do not return to the bud colony mentioned above. Instead they bud again, forming smaller aggregations in remnant pieces of woods along the Angangueo-Rosario road. These small remnants of woodland may be very important to them in offering nighttime shelter from cold and predators.
"Fires. We witnessed many fires burning in forests all over the states of Mexico and Michoacan. Fires were so frequent and dense that a permanent haze was evident in the sky. None of these were 'serious' fires such as the crown fires that we hear about in our northern forests. All were ground fires burning along the forest floors. They created a lot of smoke and locally, a lot of heat. One such fire was burning near the Chincua colony located in the Arroyo Honda about 5 km northwest of Angangueo. Although the smoke from this fire was clearly visible, it apparently has not affected the Chincua butterfly colony.
Angangueo, Michoacan, Mexico
Discussion of Challenge Question #6
"How do you suppose monarchs know when it's time to leave Mexico?"
Bryn, a 2nd/3rd grade student at Ellington School in Quincy, IL said, "I bet they notice that as the days get hotter the days also get longer!"(firstname.lastname@example.org)
Let's see how biologist Bill Calvert's answers the same question:
"What environmental cues tell the butterflies that its time to go north? These are undoubtedly the same cues that tell the butterflies that it is time to go south in the fall. The person who has done the most experimental work on the environmental factors that turn off reproduction and cause the butterflies to migrate is Bill Herman at the University of Minnesota. He believes that some combination of day length and ambient temperature is the
cue that sets monarch butterflies to migrate in the fall.
"In Mexico at the end of the overwintering period, the days are becoming longer. At the same time, daily temperatures are getting warmer. It seems likely that these same cues the monarchs use in the fall are used in reversed in the spring. That is, lengthening days and warmer temperatures tell the monarchs that it is time to go north."
Challenge Question #6 also asked, "What are the consequences of leaving too early or too late?"
In reading through students' responses, we saw that most everyone knew the monarchs risked meeting up with freezing temperatures in the north if they were to come too early. Since the monarchs are now on their way, watch the weather maps over the next weeks and record the temperatures in Texas and in the Gulf States. Have the butterflies left Mexico too early?
How many other risks you can identify which monarchs face by coming too early--or too late. Let's continue to watch over the next few weeks. In your science journal, keep track of all the factors you can.
Discussion of Challenge Question # 4
In February, Blake students visited the Mexican ejido family who owns some of the land at the Sierra Chincua monarch sanctuary. This family depends on logging as an important source of their income.
We gave you the figures the family earns in pesos and asked, "If Carmen's 8 person family spends 30 pesos
per week, how many dollars do they spend per person per week?
Ms. Bunting's 4th grade students at Richland Elementary in Quakertown, PA (email@example.com) got the same answer,
as did Nathalie and Amy of Cedar Falls Schools in Iowa (firstname.lastname@example.org).
Conserving Monarch Habitat in Mexico
As the monarchs bid farewell to the forests that sheltered them this winter, they carry with them the incredible instincts that will guide their great-grandchildren to the same forests next fall.
As we turn our attention northward to track the migration, it's important to remember: Year-round protection
of this habitat is critical to the survival of the migration--even though the butterflies spend only part of each
year in Mexico.
Many schools and organizations have already begun to raise money for monarch conservation. Over the next year,
Journey North will offer opportunities for schools to build community ties to people in the monarch region. We
hope you will join in this important effort.
Letter from Angangueo Student Luis Fernando Romero
Here's more news from Fernando--and another chance to practice your Spanish. Special thanks to Jon Dicus of Blake School for the English translation of last week's letter!
5 de marzo de 1998
The Next Monarch Butterfly Migration Update Will be Posted on March 24, 1998.
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