Monarch Migration Update: February 28, 2013
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Your Sightings!
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Estela helped gather monarch tags this week, and scientists announced a discovery: Mexico's cold winter temperatures trigger spring migration.

This Week's Update Includes:


Image of the Week
Recovering Monarch Tags Watching for Tags
Photo: Dave Kust
News: Recovering Monarch Tags
Estela Joins the Tag Team
On Saturday, Estela traveled to El Rosario to collect tags:

"We had an adventure and made some exciting discoveries," Estela reports this week.

Over 200 Recoveries
Almost all of the 200+ tags recovered at El Rosario were white Monarch Watch tags, meaning the butterflies had been tagged in the eastern U.S. and Canada. Monarchs from Michigan, Ontario, Texas, and Wisconsin were among those recovered. Tagging results like these suggest butterflies mix together at the same colonies regardless of where in the breeding range they originated.

  • Look at the trees filled with monarchs and think about all of the different places they came from!

Two Blue Tags!
To the delight of Gail and Bob Morris of the Southwest Monarch Study, two blue tags were recovered. Blue tags mean the monarchs were tagged in the southwestern United States. Compared to the eastern region, far less is known about migration from the southwest so everybody was thrilled by the discovery.

Spectacular Clusters
The monarchs were more concentrated this week, and happened to form spectacuar clusters in the center of the area open to tourists.

"With this photo, there will be no doubt for my classmates and teachers that I was really here, seeing the monarchs live," said one little girl.

Thirsty Butterflies, Dry Conditions
Moisture becomes critical at this point of the overwintering season. The colonies break up as the monarchs move downslope in search of water. This year's shortage of moisture is concerning:

"Drought in the region is alarming right now. Puddles where monarchs drink water at the Sanctuary are a 'thin thread' of running water, compared to former years," notes Estela.

The Tag Team at Monarch Butterfly Sanctuary in Mexico
The Tag Team
Monarch butterfly tags recovered in Mexico
Two Blue Tags!
Spectacular Clusters
Spectacular Clusters
Girl at El Rosario Monarch Sanctuary in Mexico
"I was here!"
Thirsty Butterflies, Dry Conditions at Monarch Overwintering Region in Mexico
Thirsty Butterflies
Scientific Discovery: Cold Triggers Spring Migration
A new study by researchers at the University of Massachusetts has shown that cold winter temperatures are needed to trigger spring migration.

"The temperature at the overwintering sites is a critical component for the completion of the migration cycle. Without this thermal stimulus, the annual migration cycle would be broken," says Dr. Steven Reppert co-author of the study.

Cold triggers monarch butterfly's spring migration

Cold Triggers Migration


The Migration: Maps and Journal
Not all monarchs go to Mexico! Before spring migration begins, please help us document where monarchs are located this winter and where milkweed is available.


Seeing Monarchs?
When you see a monarch, we want to know about it.
Monarch butterfly migration map Map of milkweed emergence: Spring 2013


(map | animation | sightings)
(map | animation | sightings)
The next update will be posted March 7, 2013.