MONARCH MIGRATION
By Vicki Rath

Migration can be defined as the movement of an animal from the place where it lives to a new place later returning to its original home. Animals migrate to avoid lack of food, shelter or because of the seasonal temperature changes. With their food source going dormant and the temperatures getting lower, the Monarch migrates. Monarchs encounter few obstacles on their migration taking advantage of the air currents and warm daytime temperatures. Cooler evening temperatures require the butterflies to swarm in the trees for the evening. Each butterfly needs certain warmth in order for them to fly.             

Every year beginning around the first of September, the Monarch Butterfly begins its annual trek south. The Monarch is native to North America with its largest population in Southern Canada and Northern United States .

The generation of butterflies born at the end of summer (the fifth generation of the year) is born larger and stronger. It also, unlike the other generations, has a repressed sexual maturation. This allows it to live as long as eight months. Previous generations live approximately a month and purposefully mate and lay eggs then expire.

The migration instinct is awakened in this “super” generation and the fat accumulated in the caterpillar stage will provide energy for its trek to México. The trip requires reserves for 2,500 to 3,000 miles with the average daytime travel speed of 10-15 miles per hour.

There are three main routes of Monarch migration. The first is to the San Diego and Santa Cruz , California area. The second is to Mexico with the third route ending in the Carolinas and Florida , some even as far as the Yucatan Peninsula, Mexico. The butterflies seen in the central part of the U. S. , from the eastern Rockies to the Great Lakes , spend their winter in Mexico .

The final destination of the Central United States Monarchs was a mystery until 1975. As early as 1952 Zoologist Fred Urquhart, a professor at the University of Toronto tagged the first Monarchs. The tag was small enough not to inhibit flight but contained an ID number and contact information.

In 1972 Mexican newspapers announced the need for volunteers to search for the tagged butterflies in order to locate the winter habitat. The first colony was located in a fir forest in the Michaocan Mountains in 1975. The temperate forest where the butterflies hibernate is humid with pine, fir and cedar trees. The number of trees keeps the temperature and humidity steady in the forest which is essential for the monarch’s survival.

When spring arrives the temperatures rise and the butterfly’s activity increases. In March the sexual organs reach maturity. Mating begins and the butterflies begin heading north again. The adults do not make it all the way back. They lay eggs and expire shortly after beginning the generational journey to their summer home.

Swarms of monarchs should be forming now. If you find one please call the Outdoor Campus (605-362-2777) in Sioux Falls with the location of the swarm. As partners with Monarch Watch, they will send out tagging crews if possible. A booklet called “Monarch Butterfly-a manuel for the environmental educator” is also available from the Outdoor Campus. The booklet contains much of the information used in this article plus much more. Activities for group learning are also included.