Today's News Report Your Sightings How to Use Journey North Search Journey North

Monarch Butterfly Migration Update: February 28, 2002

Today's Report Includes:

Field Notes from Mexico by Dr. Bill Calvert

Dr. Calvert calls in each week from Mexico.
Photo:Jim Edson

Sunday, February 24 was beautiful. Snow covered the Nevada Toluca and the usual mantle of clouds had lifted, leaving it plainly visible. Arriving at base of Herrada we found butterflies streaming down the mountain and across the highway, flooding the arroyos and taking water from the irrigation canals as well as from puddles in the road. Strangely there were few birds in the mesic (medium wet) epiphyte-filled arroyo where last week we had seen three glorious mountain trogans.

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.

Monarchs open their wings with a pulse of sunlight, becoming miniature windows of stained glass.

Nectar After the Storm
Many thousands of plants at the elevation of the butterfly colony were frozen. Some plants, especially the smaller-stature Senecios (a composite) such as prenanthoides, were unaffected by the freeze. But the high stature Senecious such as Barba johanas and Anguilifolius and the Eupatoriums were badly damaged. It is tempting to suppose that the nectar supply will be very small this season. However, below the colonies along the field edges the nectar plants are undamaged. This is where most butterflies are found nectaring in preparation for their journey north.

We have a poet along, Allison Demming, from Tuscan, Arizona. She is Nathanial Hawthorn?s great granddaughter, so the talent must run in the family. She contributed the poem below.

Until next week,

Words of a Visiting Poet

Herrada y Arroyo
By Allison Demming

At Herrada, monarchs stream down from the mountain to drink from puddles and seeps.
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.?

This falling monarch's claws caught on a moustache.

?Monarchs have incredible claws,? says Dr. Calvert. ?They are amazingly well adapted to hang on. Even though the butterflies are dormant, the claws hook on and they remain in the trees. But I have seen them fall. So cold they can?t open their wings, they float down--but with their claws extended--so they can grab something on the way down. You?ll see them catch on people?s heads, backs, clothing--everywhere. These well-developed claws are on their fore walking feet. In extremely cold weather there are descriptions of butterflies falling 'like bullets' because they can?t open their wings.? Dr. Brower added, ?Often clusters of butterflies hang with their claws interlocked, so when one lets lose you may get a whole string of them coming down.?

Human designs often mimic things found in nature. Notice how similar monarch claws look to the crampons ice climbers wear, so their feet can grip slippery ice!

Photo: Alpine Woman

Click Here to see a magnified view of the monarch?s claws from the Monarch Lab Website

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.

Eduardo Rendon-Salinas

Biologists Alfonso Alonso-Mejia, Eduardo Rendon-Salinas and Lincoln Brower studied the rate at which butterflies burn their lipid reserves during the overwintering season. Each month, the researchers took samples of butterflies that were resting on the trees. They measured the amount of lipids stored in the butterflies? bodies and watched how it changed, from November until March.

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.?

In other words, the monarchs that are visiting flowers for nectar are "running out of gas." They're so low on lipids that they resort to nectar to try to stay alive. In contrast, the monarchs in the clusters still have enough stored lipids.

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:

Challenge Question #8
"How many milligrams of lipids does the average monarch burn during the overwintering season, from November through March?"

Challenge Question #9
"A monarch tag weighs 10 mg. How many times that weight does the average monarch lose by the end of the overwintering season?"

(To respond to these questions, please follow the instructions below.)

USA Today: Volunteers Needed to Track Monarchs

The article below appeared in USA Today last week. We hope the publicity will generate more volunteers for this spring?s study. Please get ready to report your sightings! The map on the right shows where monarchs have been found this winter, outside of the colonies in Mexico.

Volunteers needed to track monarchs

Scientists are asking for the public's help in monitoring monarch butterflies' northward trek this spring. A catastrophic storm in Mexico last month killed an estimated 270 million of the orange-and- black butterflies -- nearly 80% of the entire population of monarchs - - and biologists want to learn how long it will take them to rebound. "Volunteers can help scientists assess the effect of this storm, as well as other natural and human-induced threats on monarch butterfly populations," says Elizabeth Howard, founder and program director of the Journey North Monarch Migration Project, at Besides reporting sightings, volunteers can help monitor monarch reproduction this summer through the Monarch Larva Monitoring Project.

How to Respond to Today's Challenge Questions:

IMPORTANT: Answer only ONE question in each e-mail message.

1.Address an e-mail message to:
2. In the Subject Line of your message write: Challenge Question #8 (or #9).
3. In the body of EACH message, give your answer to ONE of the questions above.

The Next Monarch Migration Update Will Be Posted on March 7, 2002

Copyright 2002 Journey North. All Rights Reserved.
Please send all questions, comments, and suggestions to
our feedback form

Today's News

Report Your Sightings

How to Use Journey North

Search Journey North