Monarch Butterfly Migration Update: February 28, 2002
Today's Report Includes:
Field Notes from Mexico by Dr. Bill Calvert
The following day we made the climb to El Rosario. It was clouded over and only once, when the clouds briefly parted, did a pulse of sun strike the colony. The clusters burst open--expanding as if adding milk to wheat puffs--and the butterflies began to bask--or fly to better basking sites. The activity resembled a bee hive with the butterflies hovering about their clusters. In a short time the clouds closed again, the baskers rejoined the clusters, and all activity stopped.
The next day, Tuesday, was perfect. Not a cloud to be seen. We made the long trek to Zapatero Canyon in the Sierra Chincua on horseback and found butterflies flying everywhere. Some were watering and a few were nectaring. Some were far from the colony flying along the escarpment or sauntering through the woods. It?s hard to describe how they traverse the woods, they never seem to be in a hurry, and stop to nectar when the opportunity presents itself. Then they fly on with no apparent purpose but to grace the woodland.
Nectar After the Storm
Words of a Visiting Poet
Herrada y Arroyo
By Allison Demming
The cars slow down for them, the busses creep, and everyone exclaims in joy.
Walking among the flurry of orange, children must be comforted,
Encouraged not to swat them away when the little beauties flutter around their faces.
And then we notice that there are two winds in the forest;
The soft sloughing high in the pines,
And the papery gusts so small.
No one could hear the wind of one butterfly?s wings,
But here in the arroyo the flapping of thousands
Plays like a miniature orchestra in the cathedral of trees.
Why Don?t Cold Butterflies Fall?
Discussion of Challenge Question #4
We asked, ?Why don?t the butterflies 'lose their grip' and fall from the trees when they're paralyzed by the cold??
Among the ideas from Mr. Phillips's students at Kanawha Elementary School in Davisville, West Virginia were these: ?Samantha, Melissa, and Lacey think that the little branchlike things on their feet stick in the bark and keep the butterflies from falling.?
Why Fly if Saving Lipids?
Discussion of Challenge Question #5
Dr. Calvert asked last week, ?If the purpose is to conserve their lipid reserves, why do you suppose monarchs fly in blizzard proportions the first chance they have after a long period of dormancy??
Once again these West Virginia students in Mr. Phillips's Class had an idea: ?Jonathan and Brett thought that they wanted to stretch their wings.?
This is exactly what Dr. Calvert suspects! ?But this is just speculation. The experiments haven?t been done yet, but people are working on it,? he says. ?The idea is that exercise may be really crucial to them. When we visited last Tuesday, it was the first warm day after a long period of cool, rainy weather. I don?t think monarchs can tolerate long periods of dormancy, and need to exercise their flight muscles. This may be some basic physiological need at the cellular level to maintain muscles. Have you seen what happens to the muscles underneath a cast that don?t get exercised? The muscles 'atrophy' (shrink). This may be the case with monarchs, but nobody has shown it yet. Basically the scientific literature says monarchs must conserve lipids. So scientists are trying to explain why they fly like crazy every opportunity they get."
Living on Lipids: Surviving the Season on Stored Energy
During their 5 months in Mexico, monarchs remain largely inactive. While they do fly out of their colonies on occasion, most of the time they are motionless, hour after hour, day after day, night after night, week after week. The butterflies must live off their stored lipid reserves--which they gained during the fall migration--all winter. At the end of the season, there must be energy to spare for mating activities and the spring migration northward.
The overwintering habitat is perfect for conserving energy: The high mountains are cold enough so the lipids burn slowly--but not so cold that the butterflies freeze.
But do the butterflies also need nectar? It?s common to see overwintering butterflies drinking from flowers when visiting the region. So a quick conclusion might be YES, nectar is important. In fact, some people argued that, by thinning the forest, more flowers would grow and their nectar could help the butterflies survive the winter.
A closer look at the flower-visiting butterflies by Alonso and his team lead to a fascinating conclusion: ?Monarchs that visited flowers at the over-wintering sites had highly depleted lipid reserves. It appears that flower-visiting monarchs do not have enough lipid reserves to migrate back to the breeding areas of the southern United States.?
Make a graph so you can see how the lipids dropped each month. Compare the lipid mass of butterflies found in clusters to that of butterflies found at flowers. What do you notice? Now try this:
USA Today: Volunteers Needed to Track Monarchs
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