Monarch Butterfly Update: March 22, 2012
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Estela's community said farewell to the monarchs this weekend with a pre-Hispanic dance ceremony. Also, the long-awaited population news was announced. How many monarchs were in Mexico this winter? The migration has now moved as far north as Kansas—in March! Why?

This Week's Update Includes:

Image of the Week
Farewell celebration at monarch butterfly sanctuaries.
Image: Estela Romero
Farewell Monarchs!
News: Riding the Heat Wave?
Surprisingly Far North
With south winds and record-breaking heat, the leading edge of the migration continued to expand rapidly last week. Two early-bird butterflies were even spotted in Kansas, more than 1,250 miles from the start in Mexico! Monarchs usually reach this latitude about April 15th.

"A very worn Monarch was seen passing north across our backyard. The milkweed has not emerged yet." March 19: Garden City, Kansas

Historic Heat Wave
For nearly two weeks, strong south winds have been blowing warm air northward from the Gulf of Mexico. This map shows the persistent weather pattern responsible. Meteorologist Andrew Feedman says this heat wave is historic. Never since record-keeping began has a weather pattern been so long-lasting, so geographically broad, so early and so extreme.

Monarch and Milkweed Mismatch?
Scientists watch the connection between migration and spring temperatures carefully. Will monarchs be fooled by this unseasonably warm weather and move north too quickly? Will their milkweed host-plant be ready? What if cold and freezing temperatures return? How could this spring's unusual weather affect the monarch's breeding success? Monarchs are at a critical time in their life cycle. Scientists watch for "ecological mismatch." Will the timing of life-cycle events be disrupted by this weather?

Numbers In, Population Down
This year's monarch population estimates from Mexico were just announced. Like a report card, the data indicate how the monarchs are doing. Compared to last year, the population is down 28%. This graph shows data collected every December for the last 18 years. Because this year's population was so far below the 18-year average, scientists are looking for causal factors.

Why the Decline?
One critical factor is deforestation of the overwintering habitat in Mexico. Another concern has been raised about milkweed-loss on the breeding habitat. Dr. Karen Oberhauser is co-author of newly published research. Her study found a 58% decline in milkweed and an 81% decline in monarch egg production in agricultural fields of the Midwest.

  • Read about Dr. Oberhauser's research in the article, "Milkweed Loss Hurts Monarchs." Challenge yourself to create a diagram that illustrates the chain of events that has led to the decline in milkweed and monarch eggs.
Migration Map Animation: March 7-14, 2012
Surprisingly Far North
Weather Pattern
Climate Central and NWS
Historic Heat Wave
Monarch Butterfly in Driftwood, Texas
Image: Chuck Patterson
True Survivor!

Monarch Butterfly Population Estimate: Graph
Numbers Down
Slideshow: How Many Monarchs This Winter?
Put the annual population data into perspective. Explore how scientists use it to reflect on past events, assess current trends, and make predictions for the future.

Essential Question
Why is it important to collect and analyze monarch population data from year to year?

How many monarch butterflies this winter?

The Migration: Maps and Journal Page
Let's find out when and where monarchs and milkweed appear this spring.
Monarch Butterfly Winter Sightings Map of milkweed emergence: Spring 2011 Worksheet: Journal Page
First Monarch
(map | animation | sightings)
First Milkweed
(map | animation | sightings)
The next monarch migration update will be posted on March 29, 2012.