I saw my first Monarch Butterfly in the garden about a week ago. It sailed around the milkweed plants a few times and took off — perhaps it was a male looking for a mate. However, yesterday a female Monarch butterfly flittered over the several swamp milkweed leaves laying eggs on a few as she went and then proceeded to try to suck up some nectar from not quite open swamp milkweed flowers.
The late summer generation of eastern North American population of Monarchs are known for their round trip migration from U.S.and Canada to the Mexican highlands and back, a trip covering thousands of miles over sometimes arid land.
While the typical lifespan of a newly metamorphosed Monarch butterfly is about two months, butterflies that overwinter in Mexico live at least 6 months, in a state of reproductive and metabolic diapause. They eventually awaken from their winter lethargy, leave their wintering grounds in March, and move north in search of flowering milkweed and begin to lay eggs. Recolonization of the most northern areas of the Monarch’s range occurs over the course of two generations of butterflies, each generation moving north hundreds of miles after completing their metamorphosis. The map below shows the time course of the migration this year.
I was surprised to see that Monarchs were sighted in the Twin Cities area on May 9, having leapfrogged the state of Iowa, perhaps in one of the warm fronts that brought the warblers north this spring. Those butterflies would not have found much milkweed or any flower nectar on which to feed. I saw this happen a couple of years ago when we had a late spring and the monarchs arrived when the milkweeds were still only 10 inches tall. This was the result of that bad timing.
Coupled with ever diminishing overwintering habitat that support fewer and fewer of their numbers, Monarch butterflies face a northward journey of many unpredictable hazards and climatic challenges. It’s really quite amazing that enough monarch butterflies survive each year to appear in our backyards.