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Art Lander’s Outdoors: Monarch Butterfly decline linked to loss of wintering habitat, breeding grounds


Their beauty and agility in flight thrills nature lovers and gardeners alike.

But this seemingly fragile insect, with its beautiful coloration and fluttering flight, is hardly a homebody.

The Monarch Butterfly (Danaus plexippus) travels long distances to complete its life cycle. They leave Kentucky and other states in the region in the fall, and head south to wintering grounds.

Monarch Butterfly (Photo from U.S. Fish and Wildife Service)

Huge colonies use air currents to travel as far as 115 miles a day to the Sierra Madre Mountains west of Mexico City where they spend the winter in cool and wet oyamel fir forests, an endangered forest-type, on mountain tops at elevations up to 10,000 feet.

Some butterflies in the eastern population join the south Florida non-migratory population. Others remain in the southern U.S. during the winter months.

While in their wintering grounds the Monarch Butterfly feeds on and reproduces on milkweed plants.

Once the winter breeding season is over in March, the newly-hatched butterflies start the annual migration cycle over again, taking to the air for the long trek back north.

Biologists and citizen scientist volunteers capture and tag the Monarch Butterfly throughout its range. Each tag consists of a small sticker displaying a unique code, which identifies the tagged butterfly and where it originated.

The length of the Monarch Butterfly migrations is astounding. Last fall the Kentucky Department of Fish and Wildlife Resources (KDFWR) reported that a female Monarch Butterfly tagged at Perryville Battlefield State Historic Site, in western Boyle County, was found months later, 1,600 miles to the south, at the El Rosario Butterfly Preserve. The Perryville Battlefield Site is one of several areas in Kentucky where pollinator-friendly habitat restoration programs are underway.

A tagged Monarch Butterfly (Photo from Monarch Watch)

“This is a very rare and exciting occurrence,” said Michaela Rogers, an environmental scientist with KDFWR. “With the help of our partners, we have tagged more than 600 monarch butterflies in the last several years. This is our first recovery.”

The El Rosario Butterfly Preserve is the largest and most visited sanctuary within the 217-square mile Monarch Butterfly Biosphere Reserve. Millions of monarch butterflies from eastern North America overwinter there, clustered together in high-elevation fir forests.

Life History

The Monarch Butterfly, a member of the family Nymphalidae, with more than 6,000 butterfly species worldwide, might be the most familiar North American butterfly.

Its range includes Hawaii, Australia, New Zealand, Spain, and the Pacific Islands. Six subspecies and two color variations have been identified.

The iconic pollinator species is easily recognizable, with black and orange wings, with a white pattern. Its wingspan is 3 1/2 to 4 inches.

The Monarch Butterfly was originally described by naturalist Carl Linnaeus in 1758.

Its life cycle has four phases: egg, larva, chrysalis (pupa), and adult.

From egg to adult takes twenty-two to thirty-seven days, depending on the temperature.

Monarch Butterfly caterpillar (Photo from U.S. Fish and Wildlife Service.)

Up to four generations are produced in one calendar year, with breeding taking place in its overwintering habitat and the states and Canadian provinces where the eastern population spends the warm months of the year.

The Monarch Butterfly must have access to milkweed plants to complete its life cycle. Without them, they can’t survive.

So a habitat restoration program must include establishing and encouraging several species of milkweed plants, genus Asclepias.

There are nine species of milkweed plants native to Kentucky, with the most widely distributed and arguably most important, being the Common Milkweed (Asclepias syriaca) and the Butterfly Weed (Asclepias tuberosa).

Females lay eggs on milkweed plants, which are the food source for the caterpillars that emerge from the eggs. Then the caterpillars form a chrysalis where the pupa undergoes its transformation into an adult. Upon emergence, the adults consume nectar for fuel and begin the life cycle all over again.

In eastern North American populations, overall wing size and the dimensions of wings vary. Males tend to have larger wings than females and are typically heavier than females. Both males and females have similar thoracic dimensions.

Females tend to have thicker wings, which are thought to convey greater tensile strength and reduce the likelihood of being damaged during migration. Additionally, females have lower wing loading than males, which means females require less energy to fly.

The Monarch Butterfly is capable of distinguishing colors based on wavelength only, not intensity. This phenomenon is termed “true color vision.” This is important for seeking nectar for nourishment, choosing a mate, and finding milkweed on which to lay eggs.

Art Lander Jr. is outdoors editor for the Northern Kentucky Tribune. He is a native Kentuckian, a graduate of Western Kentucky University and a life-long hunter, angler, gardener and nature enthusiast. He has worked as a newspaper columnist, magazine journalist and author and is a former staff writer for Kentucky Afield Magazine, editor of the annual Kentucky Hunting & Trapping Guide and Kentucky Spring Hunting Guide, and co-writer of the Kentucky Afield Outdoors newspaper column.

Population Declines

This much-beloved and important pollinator species is in trouble. Monarch Butterfly numbers have plummeted by about 90 percent over the last 20 years.

Loss of breeding habitat, overwintering habitat, intensive mowing, the widespread use of herbicides used in growing no-till corn and soybeans, and other anthropogenic factors are believed to be factors in the decline of the Monarch Butterfly and other pollinators.

For more information on pollinators, visit the U.S. Fish and Wildlife Service Pollinators website.

Kentucky’s Monarch Butterfly Conservation Plan

KDFWR and other conservation agencies have responded to the declines with increased efforts at education, research and habitat improvement for pollinators.

Kentucky’s Monarch Butterfly Conservation Plan is a roadmap for helping this species recover.

The Kentucky Wild Program of the KDFWR hosts annual events each fall from late August through early October to capture, tag and collect data on the migrating Monarch Butterfly.

At these, and other Kentucky Wild events, volunteers go into the field and work side by side with researchers working to help wildlife that face threats in our state. Visit the Kentucky Wild Program website to learn more.

Monarch Watch Program

The database of Monarch Watch, a University of Kansas nonprofit education, conservation and research program, started about 20 years ago, helps scientists gain a better understanding of the timing and pace of the Monarch Butterfly migration, the origin and routes of travel, changes in distribution across North America, and localities that may be critical to supporting the migration.

Learn more about the Monarch Watch program at www.monarchwatch.org. The website includes detailed information on Monarch Butterfly biology, butterfly gardens, migration and tagging, conservation, and links to other resources.

Establishing and encouraging native perennial milkweed plants on your property is a good way to benefit the Monarch Butterfly, and help restore populations of this iconic pollinator.


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2 Comments

  1. Mr. Smith says:

    The vast increase in corn farming in our Midwest over the past 20 years has decreased the areas where milkweed thrived. Travel across Ohio, Indiana, and Illinois and you can see square miles upon square miles where NOTHING is grown except corn. Ethanol being added to gasoline brought about the tremendous overload of cornfields. Argue it as you may but this is indeed the fact.

    • J says:

      About 40% of U.S. corn is used as livestock feed, about 27% for ethanol, and about 17% is exported. All of these uses have increased in recent years.

      Ethanol makes gasoline burn more efficiently, cutting emissions, so it has a beneficial impact on the environment. Mr. Lander is correct that establishing milkweed plants as widely as possible will benefit the Monarch Butterfly.

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