Monarch Butterfly Monarch Butterfly
Today's News Fall's Journey South Report Your Sightings How to Use Journey North Search Journey North

Monarch Butterfly Migration Update: March 12, 2004

Today's Report Includes:

Field Notes from Mexico by Dr. Bill Calvert
A happy surprise this week at the Chincua sanctuary--Dr. Calvert discovered far more butterflies than he has previously estimated. On his three earlier visits, most of the colony had simply been out of view. This time, he and his group were able to see the leading edge of the colony. The butterflies appear to cover 3-4 hectares instead of the 1/2 hectare formerly reported. This means there are actually 6-8 times more butterflies than believed. “Chincua was really a pleasant surprise,” said Dr. Calvert. “I’ll tell you. It was huge.”
Photos courtesy of Dr. Lincoln Brower, Sweet Briar College

Butterfly Colonies Can be Hard to Find: Related Links
This oversight isn’t so surprising. The butterflies are beautifully camouflaged in the trees, and can be very difficult to see. Also, the clusters can move unexpectedly to new locations from time to time. What’s more, tourists aren’t allowed into the heart of the colony, and must view from a distance. For more about colony camouflage and movement, see these related links:
Bright orange butterflies look almost grey at rest. Their closed wings match the oyamel forest.

Discussion of CQ #8
How Small is the Rosario Colony Now?

Dr. Calvert’s group decided not to visit the El Rosario sanctuary this week. There have been very few butterflies there apparently due to the devastating winter storm. Last week we challenged you to calculate the decline in butterflies from mid-winter to March. “There were 90 times the amount of butterflies in midwinter than there are now,” an Illinois student calculated.

Why Are Those Butterflies Behaving So Strangely?
(Video Clip)

If you visit the monarch colonies on a cool day, the forest floor will often be covered with butterflies. Right away, you’ll notice them moving in an unusual way, as this video clip shows:

Video clip


Observations Lead to Questions
Cultivating Keen Observers

Scientific investigations typically begin with observations of something intriguing or baffling. In turn, observations inspire questions. As you observe the video clip, create a “What I Observe/What I Wonder” chart in your science journal. Work through the following categories of questions to inspire deeper levels of observation:

After Viewing the Video Clip
Did you guess that the butterflies were shivering? Did you notice how hard the monarchs were working to warm up their muscles? If you stayed to watch, a monarch might shiver this way for many hours, with rests in between, and only move a few meters.

Why Do Monarchs Shiver?
After such observations, scientists have learned that shivering butterflies are too cold to fly. Butterflies littering the forest have usually been forced down by strong wind, rain, hail or even snow. At 10,000 feet in elevation, the over-wintering sites are often cold. Temperature in the sanctuaries can sometimes drop to zero C or even a few degrees below zero. Monarchs are paralyzed by temperatures this cold!

Shivering and crawling--but not able to fly--at 49 degrees F. How much warmer must it get before it can fly? shiver004

Try This! Shivering Simulation
Find a volunteer who's willing to shiver. Ask him to sit on the edge of his chair and shiver all the muscles in his body at once-- arms, legs, feet, and hands. How many seconds does it take until he can feel his body warming? How long until he can feel himself getting tired? How long until he begins to perspire?
Why Stay Off of the Ground?
Challenge Question #9

As you can see, shivering uses energy. Now remember, the monarchs need to save energy in order to survive the winter and to fly back north in the spring.

Challenge Question #9:
“Why do you think butterflies shiver so hard--and spend so much energy--trying to get off of the ground?”

(To respond to this question, please follow the instructions below.)

Predicting the Spring Migration Route
Are all eyes on Texas and the Gulf Coast states? Will the butterflies that over-wintered there move directly north? Or, will the monarchs that over-wintered in Mexico repopulate the entire northern breeding range?

This week, there were two separate reports of first sightings in Tallahassee, Florida. What do you make of them? Tallahassee is only about 25 miles (40 km) north of the Gulf, yet monarchs weren’t seen there all winter. Do you think the monarchs moved northward from the coast?

In Texas, the first wave of migration from Mexico should appear any day. As you track the migration this spring, predict the route the migration will take:

Ask the Monarch Expert
Open Now Until March 19

Questions are now being accepted for monarch butterfly expert Dr. Karen Oberhauser. You can read her biography on the web, prepare your questions, then:

I How to Respond to Today's Challenge Question:

1. Address an e-mail message to:
2. In the Subject Line of your message write: Challenge Question #9
3. In the body of your message, answer the question above.

The Next Monarch Butterfly Migration Update Will Be Posted on March 12, 2004

Copyright 1997-2004 Journey North. All Rights Reserved.
Please send all questions, comments, and suggestions to
our feedback form

Annenberg Web SiteToday's News Fall's Journey South Report Your Sightings How to Use Journey North Search Journey North Journey North Home Page