Migration

7 things you didn’t know about the monarch butterfly’s annual migration

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Most people tend to think of the butterfly as a solo artist, each pretty pollinator flitting from flower to flower individually. And for the most part, that’s true. Except every fall, monarch butterflies (Danaus plexippus) gather in droves for a long and incredible journey. If you’ve ever seen a group of butterflies flying together and wondered what was going on, read on for some surprising facts about the monarch’s incredible migration.

On the way south!

The monarch butterfly, also known by several other names, including milkweed (for the plant it lays its eggs on) and tiger (thanks to its orange and black striped pattern), exist in various parts of the planet, but unlike to others of their kind, they cannot stand the cold. This is why North American populations migrate south from late August to October. Monarchs found west of the Rocky Mountains head to California, while those east of the Rockies head to Mexico.

A group effort

A group of butterflies is called a swarm or, more colorfully, a kaleidoscope. Scientists believe that monarchs migrate in large groups to warm up at night, when they land in their thousands to roost in trees. There can also be an aspect of safety in numbers at work, as a traveling or resting party can look like a large creature, forcing potential predators (usually birds, lizards, and toads) to think twice. times.

RELATED: 8 Ways Your Garden Can Save America’s Most Beautiful Butterfly From Extinction

Migration of the monarch butterfly

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Major mileage

As delicate as they may seem, monarchs manage to fly between 50 and 100 miles per day on their fall migration from the northeastern United States and Canada to California or northern Mexico, where they hibernate. The entire trip is between 2,000 and 3,000 miles, but the monarchs move at a fairly rapid pace of around 30 miles an hour.

Ladies First!

Female monarchs lead the migration, with men following in their wake. Although charming ladies have smaller wings and smaller flight muscles than guys, their wings are thicker and sturdier, making them more efficient pilots, a University of Georgia study recently found. . The trip south is accomplished by a single generation of monarchs, quite impressive when you realize that the trip north in the spring takes three to four generations.

Migration of the monarch butterfly

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How many hectares?

The migration of monarchs cannot be counted in numbers; it is estimated by the number of hectares occupied by the population. (One hectare is a unit of area equal to 10,000 square meters.) During the 1996-97 season, monarchs occupied 18.19 hectares, according to the Monarch Butterfly Biosphere Reserve, while during the 2013-14 season , the number had fallen to an alarming .67 hectares. The numbers rebounded, but have risen and fallen since, with monarchs occupying 2.10 hectares in the 2020-21 season.

RELATED: How To Make A Butterfly Garden

Estimated departure times

In late summer and early fall, monarchs become sensitive to cool nighttime temperatures and the gradual reduction in daylight hours – a sign that it’s time to fly south. They also notice that the milkweed is starting to wilt and turn yellow, another indication that it’s time to move on. During their winter break, monarchs enter diapause, a hormone-controlled state of dormancy that is also sensitive to temperature changes. Once their internal alarm rings, the butterflies wake up, knowing it’s time to head north again.

Migration of the monarch butterfly

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Under siege

Although monarch butterflies are not currently in danger of extinction, their migratory process is threatened: the population of monarchs wintering in Mexico last year declined by 26 percent. The World Wide Fund for Nature cites the culprits of climate change and deforestation wreaking havoc in the monarchs’ southern hibernation territory and their northern breeding ground. Herbicides and pesticides also kill milkweed, the only plant monarchs lay their eggs on. Go here to save the monarchs by helping to reseed 1 billion square feet of meadows and wildflowers.


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