Monarch Butterflies Missing From Canada This Summer

The monarch butterflies are missing this year from Canada’s summer flowers. In a sad twist, a major study of the famous migrating butterflies’ eastern route from Mexico to Canada was just published last Wednesday in science journal Proceedings Of The Royal Society B.

University of Guelph PhD candidate Tyler Flockhart spent the summer of 2011 tracking the migration of the iconic monarch butterflies from southern Texas across 17 US states and two Canadian provinces. He logged almost 22,000 miles in the trek to document the exact journey.

Most monarch butterflies gather in Mexico for the winter. There are also some wintering colonies in California.

In the spring, they begin a multi-generation trek back north. No monarch lives long enough to make the entire journey itself. Instead, the generation departing Mexico on the eastern trail stops and breeds in Texas and Oklahoma. Then the next generation stops somewhere in the Midwest corn belt and breeds again.

And so on until they reach the northern limits of their range in Canada.

Flockhart spent a lot of time following that trail and publishing the route.

But there’s a tragic twist.

The winter of 2012 reportedly held Mexico’s smallest crop of monarch butterflies ever.

And now almost all of Canada’s monarch butterflies are missing.

Canada’s Globe And Mail posted some shocking numbers on July 31. They said that Mexico’s wintering monarchs had crashed from an average of 350 million to 60 million — a collapse of 80 percent.

And the impact on Canada? G&M called the butterfly populations “dismally low.” In Ontario, areas that would normally count 100 monarch butterflies have reported fewer than five.

CBC News blamed the lack of butterflies in Canada on what they called the crash in milkweed habitat in the US Midwest farm belt. That so-called weed is the butterfly’s only food.

Monarch butterflies gathered on the Central Coast in California

Monarch Watch’s Chip Taylor told CBC that it wasn’t enough for Ontario to plant plenty of milkweed habitat. The United States corn belt must set aside milkweed habitat as well. He wrote to CBC:

“Just because there is a lot of milkweed in some areas of Ontario does not mean this applies everywhere…It’s what happens in the corn belt that determines the size of the monarch population and milkweeds have crashed in this area.”

Flockhart’s study confirmed the importance of the US Midwest stop along the trail. A good breeding generation there allows monarch butterflies to explode outward in multiple directions, including north into Canada.

This year, thanks to the lack of wild milkweed, it didn’t happen. And that caused the migrating monarch butterflies to mostly miss Canada.

[Monarch butterfly wintering colony photo by Charles Shapiro via Shutterstock]
[top Monarch butterfly photo by James Laurie via Shutterstock]

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