Monarch butterflies facing battle royal for survival

The eastern monarch population in the U.S. has declined by anywhere from 22% to 72% over the past decade
Published: Aug. 2, 2022 at 12:18 PM CDT
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COLLEGE STATION (Texas A&M AgriLife) - The monarch butterfly has been placed on the International Union for the Conservation of Nature’s Red List as endangered.

The IUNC’s Red List is a comprehensive information source on the global conservation status of animal, fungi and plant species. It is a tool for promoting the biodiversity conservation and policy change needed to protect the world’s flora and fauna.

Texas A&M AgriLife entomologists are concerned about the decline in monarch butterfly populations and want Texans and others to understand why these “regal” insects are important to agriculture and the environment.

According to IUCN estimates, the eastern monarch population in the U.S. has declined by anywhere from 22% to 72% over the past decade, with the western U.S. monarch population declining by anywhere from 66% to 91%. Habitat loss, climate change, pesticides and disease were cited as some of the major factors in the species’ decline.

Monarch butterflies migrate from overwintering locations, the largest of which is in Mexico, to more temperate regions that can be thousands of miles from the overwintering areas. Depending on the region, multiple generations of monarch butterflies can be seen before the fall migration to overwintering sites.

In the fall, monarch butterflies begin their trek from northern locations across the U.S. and Canada to their overwintering sites in Mexico. As they move southward, most of these butterflies will converge in north Central Texas and continue their flight south into Mexico.

“Monarchs are very susceptible to environmental changes, especially during the times in their annual cycle when millions of them collect in the same general location,” said James Tracy, Ph.D., a postdoctoral research associate in the Department of Entomology of Texas A&M’s College of Agriculture and Life Sciences.

Monarch populations are especially susceptible to significant environmental changes when they are gathered together in large numbers.

“A sudden winter storm in Mexico can kill millions of monarchs overwintering there,” Tracy said. “There is also a significant amount of habitat loss from logging. Habitat loss and climate change are two major factors in the monarch’s population decline.”

Another factor affecting monarch populations is the huge reduction in supplies of one of its main sources of nutrition - milkweed. “Here in Texas, you want to be sure to cut your milkweed down in October,” she said. “Otherwise, the monarchs will lay eggs before making it to Mexico. Those eggs usually hatch and then die because the food dries up, or we get a freeze before they complete their lifecycle. This is especially true when we have warm late falls or early winters, and milkweed doesn’t die back.”

More information on what can be done to help restore monarch populations can be found at: www.monarchwatch.org.

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