Monarch Butterfly Migration News

Monarch Butterflies

Dry Habitat, Thirsty Butterflies
March 2, 2017 by Elizabeth Howard

Mexico's dry season is reaching its peak. When, where and how do monarchs obtain the water they need to survive the winter in Mexico?

Estela Romero, Journey North

Colony Break-up
Moisture becomes critical at this point of the overwintering season. By March, the monarch's winter habitat is extremely dry. There's a flurry of activity now as thirsty monarchs break out of their clusters in search of water.

Estela Romero witnessed this change at El Rosario:

"The dryness of the soil is now very considerable. As you start making your way up the staircase at the sanctuary, monarchs suddenly start flying all around you, most rushing downway, most likely looking for water sources downhill.

"This weekend, maybe due to the high tourists' flow, guards have been assigned to protect stream areas alongside so that visitors are not disturbing such areas for monarchs to land and drink."

Traveling to Water
Monarchs move down the mountain into the lower portions of the watershed in search of seeps, drainages, arroyos and most any source of water they can find. Numbers inside the sanctuary dwindle, as fewer and fewer butterflies fly back up the mountain.

Dr. Lincoln Brower emphasizes the need for conservation outside of the sanctuary:

"It’s important to protect the entire watershed so monarchs can find moisture during the final critical weeks before spring migration."

March is Departure Month
As the end of the overwintering season rapidly approaches, important changes are taking place. Mass departure from the sanctuaries will occur from mid to late March, and early butterflies may already be departing.

At the Sanctuary

Estela's Observations

Moisture is Falling

Activity is Increasing

Monarch butterflies need water at the sanctuary in Mexico.

Dust is Rising

Monarchs, Mountains, and Moisture

Morning Mist Early in the morning, the mist is engulfing the butterflies and condensing on the Oyamel fir trees.

Inside the Colony Clusters of monarchs on the Oyamels are enshrouded in mist.

Taken early in the morning on 11 December 2006, this picture shows how the condensed mist freezes on the magnificent open area on Cerro Pelon, known as the Llanos de los Tres Goberonores. In this picture, you cannot see the colony, but it is all the way down at the end, to the right, in a grove of cedar trees.

Mist to Frost Taken early in the morning on 11 December 2006, this picture shows how the condensed mist freezes on the magnificent open area on Cerro Pelon, known as the Llanos de los Tres Goberonores. In this picture, you cannot see the colony, but it is all the way down at the end, to the right, in a grove of cedar trees.

Later in the morning, in the same area, we found several thousand monarchs drinking dew. The sun's rays had fallen on the frosted ground vegetation and the frost had melted into dew. The monarchs flew out of the overwintering colony to drink the dew drops.

Frost to Dew Later in the morning, in the same area, we found several thousand monarchs drinking dew. The sun's rays had fallen on the frosted ground vegetation and the frost had melted into dew. The monarchs flew out of the overwintering colony to drink the dew drops.

Drinking Dew This monarch’s proboscis is in the grass, imbibing the dew.

This monarch failed to fly back into the clusters before nightfall. Water droplets condensed on its wings. This is a very precarious situation. The dew can freeze when the overnight temperature drop below freezing. This often happens in open areas that are exposed to the cold, clear sky.

Water on Wings This monarch failed to fly back into the clusters before nightfall. Water droplets condensed on its wings. This is a very precarious situation. The dew can freeze when the overnight temperature drop below freezing. This often happens in open areas that are exposed to the cold, clear sky.

This butterfly is a victim of a freezing event and will not survive. The frost crystals mortally wounded the butterfly. They penetrated through the cuticle and disrupted the cells. Although millions of monarchs may fly out of the colony on sunny days to find water to drink, almost all of them manage to fly back into their colonies. Only a few get stranded in open areas where they may freeze to death.

Killed by Frost Crystals This butterfly is a victim of a freezing event and will not survive. The frost crystals mortally wounded the butterfly. They penetrated through the cuticle and disrupted the cells. Although millions of monarchs may fly out of the colony on sunny days to find water to drink, almost all of them manage to fly back into their colonies. Only a few get stranded in open areas where they may freeze to death.

The high altitude mountains capture moisture through a process called adiabatic condensation. As moisture-laden air rises, it expands and cools, then clouds form. At the high altitudes, the moisture condenses as water droplets on the needles of the Oyamels and pines.

Mountains Capture Moisture The high altitude mountains capture moisture through a process called adiabatic condensation. As moisture-laden air rises, it expands and cools, then clouds form. At the high altitudes, the moisture condenses as water droplets on the needles of the Oyamels and pines.

Mist on Monarchs You can see droplets of condensed mist on both the pine needles and on the butterflies.

Mexico's dry season begins when the monarchs arrive in November and lasts until they leave in March. The air becomes increasingly dry as the months go by, drying out the forest and the butterflies. Even dew becomes scarce.

Overwintering During the Dry Season Mexico's dry season begins when the monarchs arrive in November and lasts until they leave in March. The air becomes increasingly dry as the months go by, drying out the forest and the butterflies. Even dew becomes scarce.

By March, the monarch's winter habitat is extremely dry. The colonies break up as the butterflies fly out in search of water. They move down the mountain into the lower portions of the watersheds. It’s important to protect the entire watershed so monarchs can find moisture during the final weeks before spring migration.

Colony Break-up By March, the monarch's winter habitat is extremely dry. The colonies break up as the butterflies fly out in search of water. They move down the mountain into the lower portions of the watersheds. It’s important to protect the entire watershed so monarchs can find moisture during the final critical weeks before spring migration.

Companion Resources

Driving Questions

When, where and how do monarchs obtain the water they need to survive the winter in Mexico?

Report Your Sightings


Report all monarchs you see — adults, eggs, larvae.

What to Report	Winter Adults report \| map \| list	Winter Eggs report \| map \| list

Winter Larvae report \| map \| list	Milkweed report \| map \| list	Other Observations report \| map \| list

Next March 9, 2017