Conserving Energy
February 23, 2017 by Elizabeth Howard

Monarchs can survive all winter with little or no food. How? The cool forest is the secret.

Monarch butterfly at sanctuary in Mexico in snow.
Monarchs burn less energy when temperatures are cool.
Image Estela Romero, Journey North

News from Mexico
After this week's trips to the sanctuaries, Estela Romero reported that mating is still nowhere to be seen but should begin any day. Tourists are visiting from around the world and are delighted by the butterflies' performance and splendor. She remains concerned about this winter's unusually warm temperatures.

"Temperatures have been TOO HIGH for this time of year. Everyone around in town is commenting since we know it is not normal. Even in January some bright sunny days were reaching up to 22°C. How can the monarchs stand it? Let's hope it is more bearable for them in the forests."

Abnormally warm temperatures can present a problem: If it's too warm during the winter, the butterflies can burn their stored fat too quickly.

Lipids Falling
The graph shows how lipid levels change during the five months the monarchs are in Mexico. Their fat reserves should be about half gone by now. Have this winter's warm temperatures caused the butterflies to burn lipids more quickly? Running out of fat is a concern. Monarchs need enough fuel to survive the winter and to migrate north in the spring.

The secret behind the monarch's survival without food is the cool habitat it chooses in Mexico. "Cool temperatures in the forest slow down the monarchs' metabolism so they can stay alive longer," says Dr. Karen Oberhauser.

Monarch butterfly at sanctuary in Mexico.
Letter from Estela
Monarch butterflies survive winter in Mexico in the cool forest sanctuary.
Lipids Falling
Monarch butterfly at sanctuary in Mexico in snow.
Cool Forest Habitat

Surviving the Winter on Stored Energy


Companion Resources

Monarch butterfly at sanctuary in Mexico in snow.


Photo Gallery

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Teaching Suggestions

Driving Question

Monarchs can survive five months of winter in Mexico with little or no food. How does the forest habitat make this possible?


Report Your Sightings
Report all monarchs you see — adults, eggs, larvae.
Monarch butterfly migration map Monarch butterfly migration map Monarch butterfly migration map
What to Report Winter Adults
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Winter Eggs
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Monarch butterfly migration map Map of milkweed emergence: Spring 2017 Monarch butterfly migration map
Winter Larvae
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Other Observations
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Next March 2, 2017