Have you, like me, noticed a lot of monarch butterflies lately? My daughter and I saw one in our backyard a couple days ago. then yesterday I saw a couple fluttering by in the front yard. Today (September 7) I watch a Monarchs skirt the hood of my car in the radio station parking lot.

Once was cool, twice was a codiance, but three in three days means something is going on. Yep, it's the annual fall monarch butterfly migration.

North America’s monarch butterfly is the only known butterfly to have a north/south migration like birds. The monarch cannot make it through the cold winters like other butterflies do. Other species often survive in their larva or pupa stage. But, monarchs traverse North America each year.

During the end of summer and into the fall, monarchs that live east of the Rocky Mountains make their way to Mexico. Those on the other side of the Continental Divide winter in California.

Monarch Butterfly Fall Migration Patterns. Base map source USGS National Atlas

 

Monarchs from all over the east will converge in Texas and head for the Mexican state of Michoacán. They will stay there until March when they migrate back north.

Monarchs roost for the winter in oyamel fir forests at an elevation of 2,400 to 3,600 meters (nearly 2 miles above sea level). The mountain hillsides of oyamel forest provide an ideal microclimate for the butterflies. Here temperatures range from 0 to 15 degrees Celsius. If the temperature is lower, the monarchs will be forced to use their fat reserves. The humidity in the oyamel forest assures the monarchs won’t dry out allowing them to conserve their energy.

The monarch colonies can get so big in the trees that the cluster of butterflies has been know to break branches.

Source: USDA Forrest Service


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