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Monarch Butterfly Migration Update: March 28, 2002

Today's Report Includes:

Strong and Steady, Migration Continues Across Texas--and Eastward
The monarchs fanned northward and westward across Texas during the last week, and the leading edge of the migration clearly appears to have expanded into the states of Louisiana, Mississippi and even Arkansas!

Coastal areas of Texas traditionally report the highest numbers in Texas each spring, and this year?s records certainly reinforce the pattern:

At Padre Island National Seashore near Corpus Christi, TX, Darrell Echols counted 200 monarchs, in two groups of 100! Mike Quinn noted that, to date, this is the largest number of Monarchs reported from Texas this spring. What?s more, ?Darrell's report is an order of magnitude greater than any Monarch reports received all last spring!? said Mike.

On Matagorda Beach last Thursday, March 21, Linda and Richard Serrill counted, ?A good, honest 100 butterflies in all.?

Observers in Central Texas are also noticing what they consider to be large numbers this spring for their region:

?In my 5 years here, I have never seen so many spring monarchs,? wrote Ronald Hood from the central Texas town of Tarpley. In the 5 days following his first sighting he observed a daily flow of monarchs, sometimes at a rate of 3-5 an hour."

Austin?s Chris Durden commented on the 21: "This is the first spring of 34 observed in central Texas that I have seen abundant monarchs. Beginning 14th March, I have seen monarchs daily, up to six at a time, and almost all day long, and even during rain."

Let?s look at the migration pattern in Texas during the past two weeks. If we group Texas sightings according to week, the mean latitude of the migration moved north, expanding from 29.08 N to 30.90 N. It also filled out to the west, with the mean longitude shifting from -95.14 W to -97.87 W.





Week #1

12-18 March

29.08 N

-95.14 W

Week #2

19-26 March

30.09 N

-97.87 W

Challenge Question #15:
?How many miles to the north did the mean latitude of the Texas sightings move, based on data collected during the past two weeks? (Clue: One degree latitude equals 69 miles.)?

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

What About That North Carolina Monarch?
On March 20 came this surprising report, courtesy of Monarch Watch:

?Today we sighted our first monarch of the season. This is a surprisingly early sighting for us here in eastern North Carolina. The Monarch was bright and fresh looking like it was newly hatched. Could someone locally be raising them? We reside near Morehead City, in eastern North Carolina, on the Neuse River.?

Find the Morehead City, NC, sighting on today?s migration map. How does the location compare to others on the map?

Challenge Question #16:
?How do you interpret the sighting from the coast of North Carolina? Do you think this butterfly came from Mexico? Why or why not? Explain.?

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

Monarchs and Spring Flowers
Discussion of Challenge Question #14
We wish we had more pictures of monarchs on spring flowers, and wondered whey we don?t. So we asked, ?Why is it so much easier to find pictures of monarchs feeding on fall flowers??

Amazingly, 2nd graders Emily and Garrett in Ferrisburgh, Vermont figured this part out for themselves: ?On the way back to Vermont, a lot of the butterflies don't get here. A lot die. But the ones that come back, lay eggs. So in the fall, there are a lot more butterflies around, so there are more chances to take a good picture.?

It?s true! There are far more monarchs in the fall. The continental population is at its lowest each spring, when the butterflies are returning from Mexico. With each new generation there are more and more butterflies on the wing. The population is always at its peak in the fall, so it?s easiest to find and photograph monarchs at that time.

Monarchs on Fall-blooming Flowers

And there?s another interesting reason:

?Monarchs are so intent on nectaring during the fall migration that you can actually, if you're really careful, sneak up with your thumb and forefinger and just grab one right off of a flower,? says Lincoln Brower.

So taking a picture in the fall is a snap. The monarchs are eating desperately in order to build up the lipids they?ll need for the fall migration and for surviving the overwintering season. They?re so busy eating that they?re much more tolerant of people with cameras. In the spring and summer, nectar is needed only to sustain the butterfly during its brief life as it goes about its daily activities. Photos are more difficult to capture because the butterflies are more skittish, and seem to scare off of a flower much more easily.

Looking at Lipids

As the graph at the right shows, spring and summer monarch generations have a mean lipid mass of only 20 mg. In contrast, those that reach the Mexican sanctuaries in November have a mean lipid mass of 180 mg--that?s nine times greater! (Adapted from Alonso-Mejia, A.A., E. Rendon-Salinas, E. Montesinos-Patino and L.P. Brower, 1997. Use of lipid reserves by monarch butterflies overwintering in Mexico: Implications for conservation. Ecological Adaptations 7:934-947.)

Milkweed Emerging Along the Migration Trail

Please help monitor the spring emergence of the monarch's food plant across North America. You?ll be amazed at the close connections between monarch migration and this all-important plant. This map shows where observers have reported milkweed emerging so far:

Seventh grade students Mary, Kristin, and Kate of Texas Military Institute are monitoring native milkweed near San Antonio, TX. They found 17 eggs on 30 plants on March 24th! ?These are our first eggs on native milkweed this spring,? they reported. Their teacher planted milkweed last Wednesday and by Friday afternoon there were already 2 monarch eggs!

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 # 15 (or #16).
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 April 4, 2002

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