Monarchs on the move

The amazing monarch!

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Outweighed by a penny and powered by wings no wider than a toddler’s hand, the iconic monarch (Danaus plexippus) is right now embarking on the first stage of a migration that will cover upwards of 3000 miles, with some individuals traveling over 200 miles in a single day! They will wind their way across mountains, deserts, and cities, through multiple seasons and weather extremes, in a round-trip effort that will span five generations.

Monarchs in the United States are split into two populations, one east of the Rockies and the other west, along the Pacific Coast. The western monarchs spend their winter in California. Those to the east winter in the mountainous oyamel fir forests of southern Mexico.

It’s now in early spring when the eastern monarchs descend from the oyamel firs and move northward through Texas, allowing us to re-appreciate their beauty and marvel at their incredible stamina, navigational abilities, and the unique spectacle that is the monarch migration.

An epic journey

As temperatures warm and days lengthen, monarchs finish their development which was suspended over the winter, become reproductive and begin mating with fervor. Once mating completes, around February and March, the females leave the males behind in Mexico and head for the milkweed that is now sprouting across Texas.

And so the migration back to the United States and Canada begins.

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Used with the permission of the Xerces Society  https://xerces.org/monarchs/

The energy expended to complete this first leg of the journey is tremendous. After six weeks or so, now March and April, the female monarchs must find a milkweed leaf on which to deposit their eggs before they die. Once laid, four days will pass before the eggs hatch into voracious eating machines – baby monarch caterpillars.

Monarch caterpillars feast night and day on the leaves of their host plant and, incredibly, will gain 200 times their body weight in just two weeks. When the feasting ends they form their chrysalis and spend the next 10 days metamorphosing into an adult butterfly, vibrating with color and ready to renew the march north. This is generation 1, the offspring of the butterflies that overwintered in Mexico.

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Monarch chrysalis

Several more generations will live and die over the summer, travelling further afield, but just one generation will make the entire journey back to the oyamel firs beginning in October.

The fall migration is even more dramatic than the spring, after reproduction has bolstered the population, dozens and even hundreds can be spotted hourly.

Creating safe havens for pollinators in our yards and communities provides vital waystations during spring and fall migrations.

The migration in crisis

Once 700 million strong, monarch populations have now crashed. It’s estimated the eastern population has plummeted by more than 85% while the western population is suffering even more – only 28,000 were counted this winter. Multiple issues are to blame:

Habitat loss and fragmentation. Over 160 million acres of monarch habitat has been lost to development since 1996.  Illegal logging of the overwintering sites in Mexico is also taking a toll.

Climate change. The increased frequency and intensity of extreme weather events can devastate migrating populations. Because of the incredible density of monarchs in the overwintering grounds, severe freezes there are catastrophic.

Pesticides and herbicides. Milkweed used to grow throughout corn and soybean crops across the south and midwest. But herbicides have driven milkweed to near extinction in these agricultural landscapes and depleted monarch populations along the way.  Monarchs are also being impacted by neonicotinoids, a new class of insecticides that spread their toxins through the plant’s tissues. Caterpillars that dine on these plants quickly perish.

OE. Ophryocystis elektroscirrha (OE) is a parasite that infects monarchs, causing them to die in the pupal stage or emerge deformed. Milder infections result in shorter life spans and an inability to fly properly. OE pervades in our area as non-native tropical milkweed (Asclepias curassavica) continues to grow through the cooler months, after native milkweeds have died back. Follow these important steps if you choose to grow tropical milkweed.

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Monarchs overwintering in the oyamel fir forest of Mexico

What You Can Do

Join The Woodlands Township Plant for Pollinators Program. Through this program you can…

Learn

  • Get notified of upcoming lectures, classes and workshops by signing up for the Township’s Environmental Services blog and calendar updates. These free events focus on pollinators, native plants, invasives removal, organic gardening, no-chemical pest control and more.
  • Ask for a presentation on the Plant for Pollinators program and how to create habitat from the Township’s team of Environmental Education Specialists.
  • Follow the monarch migration with Journey North, check out the Pollinator Partnership’s Million Garden Challenge and more with these partner links.

Grow

Choose a sunny spot

Volunteer

  • Volunteers are needed for larger community planting projects. Help to weed, seed and spread habitat for all types of pollinators. Contact enviro@thewoodlandstownship-tx.gov if you or your group can lend a hand.

Observe

  • Download the easy-to-use iNaturalist app on your phone and monitor your habitat for monarchs and other pollinators. Your findings will support the Plant for Pollinators Project. It’s also a great way to learn more about nature!

A wondrous journey

The first sighted monarch, migrating from the United States to its overwintering sanctuary deep in the mountains of central Mexico, reached its destination on November 6th, as reported by Journey North. Soon it will be joined by tens of thousands. Then by hundreds of thousands.

The spring and fall migration of the monarch butterfly is truly an amazing phenomenon. The monarch is the only butterfly known to make a two-way migration, similar to birds. Unlike other butterfly species that can overwinter here as larvae, pupae, or even as adults in some species, monarchs just can’t make it through our cold winters.

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Using clues from the environment, monarchs know when time is approaching to move on. Scientists believe shortening days and lowering temperatures, along with aging milkweed and nectar sources trigger a change in monarchs. And it’s this change that makes the monarch migration even more extraordinary: monarchs are the only known species to have a multi-generational migration.

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a generation unlike the others

Generally, monarchs produce four generations a year. The first three generations are bred and born in the United States after they arrive during the spring migration north from Mexico. Each of these generations makes its way northward with some reaching as far north as Canada. Individuals of the first three generations live from two to six weeks.

When the fourth generation is born, something happens—and what happens, exactly, is unknown. What is known is that this generation enters reproductive diapause as adults and can live as long as nine months. These are the little guys that make the great trip south, starting in the late summer (in the north) and fall. Somehow, this generation of butterflies knows exactly where they’re headed while never having been there before: the high elevation oyamel fir forests in the Transvolcanic Range of central Mexico. The trip can be an astonishing 3,000 miles long for the northern-most butterflies and can take about two and a half months to complete.

It is hard to contemplate a world without the monarch—it’s woven into the very fabric of our culture. But the monarch migration is now recognized as an “endangered biological phenomenon” by the International Union for the Conservation of Nature and our northern neighbors in Canada have already identified the monarch as a species at risk.

To see the monarchs gather in Mexico over the winter months is something to behold. Watch this short video by National Geographic to get a glimpse of a monarch sanctuary in Mexico:

more interesting bits about the monarch’s incredible journey…

  • Although the monarch migration is visible from the ground, glider and airplane pilots have reported monarchs flying at heights from 1200 to as much as 10,000 feet.
  • Monarchs have two speeds: powered flight (greater than 12 miles per hour) and gliding.
  • When gliding, monarchs catch thermals to gain altitude and then glide south to southwest with the help of the wind. If conditions are favorable, monarchs can maintain altitude by flapping their wings only once every 20 to 30 feet.
  • Flight requires sunny days, light winds, and temperatures greater than 55 degrees. Headwinds greater than 10 miles per hour and temperatures greater than 88 degrees impede migration.
  • Tracking migrating monarchs from various starting points in the interior United States shows that no matter where they begin their journey, they all fly, more or less, on a direct path toward central Mexico. Scientists don’t know how the butterfly determines its particular geographically appropriate direction.
  • Although the total migration advances southward only 25 to 30 miles per day, individuals have been recorded to have covered hundreds of miles in just a few days.
  • Monarchs overwinter in dense clusters on oyamel firs in a semi-dormant state. They become active when temperatures rise above 55 degrees to find water. Nectar is not required—they live off stored fats all through the winter months.

One late season monarch averaged 61 miles per day for two weeks while flying from Virginia to Texas.

See Journey North’s  interactive map to see the progress of the fall migration. And if you have citizen scientist interests, consider adding your monarch sightings in their interactive spring 2019 migration map.

What a perfect time to contemplate a new or improved pollinator garden to make ready for the spring migration back north!