Monarch Butterfly Migration Update: March 1, 2000
Today's Report Includes:
Field Notes from the Mexican Monarch Sanctuaries
Thanks to Dr. Bill Calvert for today's news from his recent trip to Mexico:
Streams of Butterflies Flowing Down the Mountain
"It was late morning and the sight we saw was to remember for a lifetime. Millions (probably only hundreds of thousands, but it looked like millions) of orange butterflies were descending the mountain side in perfect tandem flight--all perfectly spaced and flying within a few feet of the ground.
"They poured out of the canyon and up onto the road because the road blocked their passage. Some flew on into the lower arroyo, but most turned and flew along the road. They filled the road from one side to the other, and brought traffic to a crawl. The sight of so many orange creatures flying in one direction in a harmonious union was overwhelmingly beautiful. I've come to call this type of flight "sheet flow" because the flight is so controlled and synchronous that the butterflies appear to form a seamless, flowing sheet.
"The purpose of their descent was clear to understand. The monarchs often fly out of their colonies in late winter to take water, nectar (if available), and perhaps to exercise. But why do they fly in such a controlled and synchronous manner? In early November when they arrive into the area, their flight is much different. They tower above the mountains and seem to be flying in every which direction and at every altitude. Their flight is not in unison and is not harmonic. It seems random. It is the synchronous, harmonic flight of millions of individuals that astonishes us. We simply don't know why they do this. But the fact that this behavior occurs every spring--and not at other times of year--must hold some meaning.
The Cloud Effect
Challenge Question #10
"When the cloud comes, all the butterflies that were basking immediately push off into the air. The sound of their wings, which is normally a soft din resembling light rain, increases audibly to a noise like a bee hive. The recently airborne butterflies fly around until either one of two things occurs.
1) The sun returns--and the butterflies resume basking in exposed positions as they were before. Or:
2) The cloud remains--and the butterflies abandon their exposed positions and fly back to their clusters in more protected areas of the forest.
"The behavior, which is dazzling to witness, is thought to serve an important purpose:
Why Do Monarchs Shiver?
Discussion of Challenge Question #9
As Dr. Calvert explained last week, monarchs shiver when they are too cold to crawl well or to fly. They don't need to shiver on a warm day in the sanctuary. However, Dr. Calvert visited the sanctuary on a very warm day and noticed that certain monarchs were shivering. These butterflies had been drinking water. We asked, "Why do you think monarchs that were down on the ground drinking water were shivering?"
The cold temperature of the water caused the butterflies' body temperatures to drop. So just as happens when cold air cools the butterflies, these butterflies had to shiver to warm their muscles enough to move off of the ground.
We also asked, "Why do monarchs work so hard to stay off of the ground?"
Ashley, in Vero Beach, FL suspected predators and hazards. She wrote "Monarchs stay off the ground because they can get stepped on or ants can start chewing their legs before it can escape. That's why monarchs stay in trees."
There is another threat that may play a role. It's colder and wetter on the ground. So, if it's cold that particular night, the butterflies are in more danger of freezing. Butterflies try to move up off of the ground and into the trees because the forest is like a protective blanket that protects them from the wet and cold.
Why Measure Dew?
Discussion of Challenge Question #5
In addition to measuring temperatures, the students at Pedro Ascencio school are also noting whether there was dew ("rocio"), frost ("helado") or none ("nada") present in the morning. Why is this important? This region of Mexico is dry tropical forest. Because the monarchs are here during the dry season, sources of water can be scarce. The monarchs can drink dew early in the season (Nov/Dec), but as temperatures drop (Jan/Feb), dew is no longer available and the butterflies must fly to open sources such as streams and seeps to drink. By noting whether dew or frost is present, we know if this important source of water was available to the monarchs that day.
Eligio Garcia Reports Movement of the Sierra Chincua Colony
What is an Ejido?
Discussion of Challenge Question #3
Eligio says the monarchs are now on land that is owned by an ejido. Challenge Question #3 asked, "What is an 'ejido' and what do 'ejidos' have to do with monarch conservation?"
In the dictionary, the Spanish word "ejido" means "commons". In Mexico, an ejido refers to a community of people who share ownership of their land. The ejidos are made up of groups of families. Most of the land in the monarch sanctuaries is private land that is owned by ejidos.
Who Owns the Monarch Sanctuary?
Coming Next Week
History of Land Protection in the Sanctuaries
In the meantime, think about this:
Life in the Sanctuary Region: Miguel the Breadmaker
If you travel to Angangueo to see the monarchs some day, watch for Miguel the Breadmaker and "Laura", his red 1969 Volkswagon van.
We hope you enjoy this whimsical piece about a small family business in the mountain village of Angangueo. Watch for a new story each week, in both English and Spanish, about the lives of the people who live in the sanctuary region.
How to Respond to Today's Monarch Challenge Questions|
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