The Monarch Butterfly
Each autumn as days shorten and temperatures drop, a number of natural events occur in plants and animals. Trees turn gold and crimson. Ducks, geese, and other species of migratory birds begin to move out of the north into areas of more abundant food. Many insects spend the winter as eggs or larvae and dehydrate themselves to keep from freezing. But, one unique insect has a different survival strategy - the monarch butterfly (Danaus plexippus)
Like migratory birds, monarch butterflies have evolved the ability to fly long distances, escaping winter cold and the absence of food. Decreasing day length and cooler temperatures tell monarchs that emerge in the early fall not to breed. Instead they begin the immense journey across North America, over unfamiliar terrain, funneling through Texas, to nine high mountain sites in fir forests of Central Mexico. They arrive at the overwintering areas by November, remaining there until March of the following spring. Then they return to Texas and the southern United States to lay eggs on freshly sprouted milkweeds. By late spring most from this spring generation have left the Gulf coastal states and are breeding further north. By the beginning of June they have reached the northern U.S. and Canada where they continue to breed all summer.
Texas is an important state in monarch migration because it is situated between the principal breeding grounds in the north and the overwintering areas in Mexico. Monarchs funnel through Texas both in the fall and the spring. During the fall, monarchs use two principal flyways. One traverses Texas in a 300-mile wide path stretching from Wichita Falls to Eagle Pass. Monarchs enter the Texas portion of this flyway during the last days of September. By the third week of October, most have passed through into Mexico.
The second flyway is situated along the Texas coast and lasts roughly from the third week of October to the middle of November. In selected locations, monarchs may be seen migrating in the tens of thousands. Look for the largest numbers during the second and third weeks of October in West-Central Texas, from San Angelo to Bracketville to Eagle Pass. Texas parks in this zone are especially good places to find monarchs. Many locations along the Devils, Llano, Frio, and Sabinal Rivers are also good. Call ahead to parks in the area to see if the monarchs have arrived. If monarchs are there, you must move quickly. With hot, moist weather and southerly winds, they will remain in an area, but will leave immediately with a passing front.
Below are some programs where anyone can get involved in collecting data on these unique butterflies:
Journey North engages students in the study of wildlife migration and seasonal change. Citizen scientists track the monarch butterfly migration each fall and spring as the monarchs travel to and from Mexico. Report your own observations of migrating butterflies to real-time migration maps. Share data to help scientists understand how monarchs respond to climate and changing seasons.
The Monarch Larva Monitoring Project involves citizen scientists from across the United States and Canada. Researchers at the University of Minnesota developed this program to collect long-term data on larval monarch populations and milkweed habitat. The focus is on monarch distribution and abundance during the breeding season in North America.
MonarchWatch is a citizen-science project based at the University of Kansas. This project involves volunteers across the United States and Canada who tag individual butterflies to assist scientists in studying and monitoring monarch populations and the fall migration. The tagging program helps answer questions about the geographic origins of monarchs that reach Mexico, the timing and pace of the migration, mortality during migration, and changes in geographic distribution.
