Monarch Butterfly Update: February 23, 2012
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Monarch butterflies are poisonous to most predators, but millions are eaten during the winter season. Who are the monarch's enemies in Mexico, and how do the butterflies defend themselves?

This Week's Update Includes:

Image of the Week
Monarch Butterfly Sanctuary Video Clip
Who Ate the Monarch?
News: A Spectacular Show at the Sanctuary
It's late February. Warmer temperatures and sunshine activate the monarchs, and mass flights become more common. The monarchs burst out of their tight colonies and fill the sky in a butterfly blizzard. This is the best time for tourists to visit. Estela went to the sanctuary this weekend to capture visitors' impressions. Said one:

"I was stunned when we reached the sanctuary. I could not believe my eyes when I saw the spectacular number of butterflies on the trees!"

Recovering Monarch Tags
Thousands of people tag monarch butterflies each fall. Everyone hopes their monarch will make it to Mexico, and dreams that their tag will be found. Several hundred tags are recovered each season. How? This coming weekend, Diane Pruden will travel to the sanctuaries to recover found tags as a Monarch Watch representative. For each tag recovered Diane will provide a 50-peso reward. People, like the boys in this photo, watch carefully for the tiny white tags. They know Monarch Watch will be coming soon. Estela plans to travel with Diane next weekend as a helpful guide, translator and our local reporter. Watch for her story next week.

  • To provide financial support for this effort please contact Monarch Watch.

Winter Population Size?
We are still waiting for the Mexican government to release news about the size of this winter's population. The measurements are made in December, so reflect the early-season status of the population before winter mortality. For example, predators alone can reduce the population by 15%. Winter storms, starvation and other causes of mortality take untold numbers each season. Thus, when spring migration begins, the population will be smaller than the annual December data show. Despite these limitations, these data are the best annual measure scientists have. We'll provide the information as soon as it's released.

Interview with Vistors at El Rosario Monarch Sanctuary
Photo: Estela Romero
A Spectacular Show
Interview with Vistors at El Rosario Monarch Sanctuary
Photo: Estela Romero
Meet the Tourists
Recovering Monarch Tags
Photo: Dave Kust
Recovering Tags
Population Estimate: Monarch Butterfly Overwintering Region
Winter Population Size?
Slideshow: Monarchs and Their Predators in Mexico
Monarch butterflies are poisonous to most predators. However, some animals can eat monarch butterflies, and millions of monarchs are eaten during the winter season in Mexico. Explore this question:

Essential Question
Who are the monarch's predators in Mexico and how do the butterflies defend themselves?

Journal page

The Migration: Maps and Journal Page
Before spring migration begins, please help document where monarchs are being found and where milkweed is available.
Monarch Butterfly Winter Sightings Map of milkweed emergence: Spring 2011 Journal Worksheet: Monarch Butterflies and their predators in Mexico.
First Monarch
(map | animation | sightings)
First Milkweed
(map | animation | sightings)
The next monarch migration update will be posted on March 1, 2012.