Monarchs on the Move

This is the time of the year when monarch butterflies migrate 2,500 miles from the northern U.S. to the mountains of Mexico. The peak of migration through the Grandfather Mountain area will be between September 13th and 19th.

"This is the most monarchs I've ever seen on the Mountain," said Naturalist Jesse Pope, "and it is still early in the migration season."

Monarchs rely on the sun and the seasons to warm their bodies, so when temperatures begin to drop each fall they get the signal that it is time to move south for the winter.

The migratory generation is biologically and behaviorally different from monarchs that emerge in the summer. Spring and summer generations live only six to eight weeks. The migratory generation lives seven to eight months and will not mate or lay eggs until the following spring. All of their energy will be dedicated to the migration.

Over the coming weeks the butterflies will travel up to 50 miles per day, gliding on the wind whenever possible to preserve their strength. Guided by the sun and the Earth’s magnetic field, the migrating butterflies will stop to nectar along their route, refueling their flight and building fat stores in their abdomens that will sustain them through their winter hibernation.

Monarch watch programs and migration counts are common all along the butterflies' route. Grandfather naturalists plan to participate in an Audubon Society-sponsored monarch count in the Alleghany County area this September.

"I will learn more about how to do a migration count so maybe we can add a program like this to our schedule," said Pope.

Monarchs west of the Rockies travel to small groves of eucalyptus trees along the California coast. Those east of the Rocky Mountains fly farther south to Oyamel forests 8,000 to 12,000 feet high in the mountains of south of Mexico City. Here high humidity and temperatures between 32 and 59 degrees will keep their bodies safe as they huddle together for warmth, with tens of thousands of butterflies clustered together in each tree.

When the monarchs emerge from hibernation in February they finish the development they halted prior to their migration. They become reproductive, breed, lay the eggs of the new generation and begin the journey back north to the United States.

Generation 1 monarchs are offspring of the monarchs that hatched in the fall, migrated and over-wintered in Mexico. Eggs laid early in the spring will live six to eight weeks as they develop from egg to caterpillar to chrysalis to butterfly, depositing the eggs of the next generation before they expire. It will take three to four generations to complete the journey north.

As with most living things, the main danger to the monarch butterfly is human encroachment upon its habitat; specifically logging in the forests where they spend their winters and crowding out of the milkweed plants that they depend upon along their migration routes.

Monarchs lay their eggs on milkweed plants. The emerging caterpillars feed solely on milkweed and eat enormous quantities as they grow to 2,700 times their original size in only two weeks, molting five times in the process. Milkweeds contain chemicals that make the adult bitter-tasting to birds. Predators have learned to associate the bright colors of the monarch with bad tastes and have learned to stay away.

For families, planting milkweed is an easy way both to see more monarchs and to contribute towards their conservation. There are more than 100 species of milkweed native to the various regions of North America. The variety found at Grandfather is called common milkweed and grows all across the eastern Unites States.

The Mexican government took steps to protect the monarch's winter habitat in 1986 by creating the Monarch Butterfly Special Biosphere Reserve. In the year 2000, that reserve was enlarged from 62 to 217 square miles, and with the encouragement of the World Wildlife Fund the management plan includes economic incentives to encourage participation in conservation endeavors by surrounding communities.

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