Monarch Butterfly Migration News

Monarch Butterflies

The Overwintering Season
January 2017 by Elizabeth Howard

Explore the monarch's winter habitat in Mexico and see what happens while the butterflies are there.

Only 12 places have the habitat the butterflies need to survive for the winter. The region is outlined with an orange rectangle on the map below.

Overwintering Region Only 12 places have the habitat the butterflies need to survive for the winter. The region is outlined with an orange rectangle on the map above.

Concentrated in Colonies The butterflies in a colony crowd together so tightly there can be 15,000 butterflies on a single branch.

The fact that monarchs migrate to spectacular winter sanctuaries in Mexico was not known until 1975. A Canadian biologist, Dr. Fred Urquhart, had been searching for nearly 40 years. National Geographic announced the discovery in the August, 1976.

Announcing the Discovery The fact that monarchs migrate to spectacular winter sanctuaries in Mexico was not known until 1975. A Canadian biologist, Dr. Fred Urquhart, had been searching for nearly 40 years. National Geographic announced the discovery in the August, 1976.

When scientists traveled to the region they found a landscape of volcanic mountains, rising to 10,000 feet in elevation. That's nearly two miles above sea level!

High Mountain Habitat When scientists traveled to the region they found a landscape of volcanic mountains, rising to 10,000 feet in elevation. That's nearly two miles above sea level!

Oyamel Fir Forest They found the monarchs clustered together in colonies in a forest of fir trees called "oyamel" ("o-ee-ya-mel").

Scientists later learned the oyamel forest is very rare in Mexico. Take a look! This vegetation map shows the only places where oyamel forests grow in Mexico.

Very Rare Habitat Scientists later learned the oyamel forest is very rare in Mexico. Take a look! This vegetation map shows the only places where oyamel forests grow in Mexico.

Scientists were surprised to find the monarchs in such a cold place. Overnight temperatures often drop below freezing and sometimes it even snows! They wondered why monarchs would fly across the continent to a place that's so cold.

Surprisingly Cold Scientists were surprised to find the monarchs in such a cold place. Overnight temperatures often drop below freezing and sometimes it even snows! They wondered why monarchs would fly across the continent to a place that's so cold.

There are a few flowers in the forest, but not enough to feed millions and millions of monarch butterflies all winter. How could the monarchs survive for 5 months in a place with so little food?

Few Flowers There are a few flowers in the forest, but not enough to feed millions and millions of monarch butterflies all winter. How could the monarchs survive for 5 months in a place with so little food?

Ever since the discovery in 1975, scientists have been trying to understand the monarch's basic biological needs. They are still learning about the unique conditions, or microclimate, of the oyamel forest and why it's critical for monarch survival.

A Magnificient Mystery Ever since the discovery in 1975, scientists have been trying to understand the monarch's basic biological needs. They are still learning about the unique conditions, or microclimate, of the oyamel forest and why it's critical for monarch survival.

The fact that the monarchs can survive for five winter months in Mexico is as amazing as their spectacular migration. Monarchs and their spectacular migration are known worldwide.

A World Treasure The fact that the monarchs can survive for five winter months in Mexico is as amazing as their spectacular migration.

What happens month-by-month while the monarchs are in Mexico?

Monarchs arrive in November and depart in March. Here's what takes place during the winter season:
November		December

Arriving Throughout the month, monarchs continue to arrive from the north and settle in at the 12 traditional wintering sites.		Being Counted Scientists visit the 12 wintering sites and measure the surface area the colonies cover. Results will be released by March, 2017.

January		February

Surviving Cold Watch the weather! At this coldest time of year, monarchs are at the greatest risk of mortality from deadly winter storms.		Preparing to Migrate Monarchs that survive four winter months will mate and begin the journey north in March. Join us for weekly updates on Feb. 9, 2017.

Report Winter Sightings


Seeing Monarchs? Please continue to report all sightings. Help document where monarchs are present during the winter months.
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Next Update February 9, 2017