The Historic Importance of the Prairie Ecosystem to Monarchs

Liatris is a favorite fall nectar source for monarchs migrating on the prairie

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Why do monarchs migrate, we wonder as we witness their spectacular migration. The ultimate cause is tied to their evolutionary history, say scientists. "We are quite sure that the ancestors of monarchs were tropical butterflies that could not survive long periods of very cold weather," says Dr. Karen Oberhauser. "Many people think that monarchs evolved in the tropics, and just move north each spring to take advantage of all the milkweed we have in the summertime. When monarchs moved into areas that had cold winters, they never evolved the ability to tolerate these winters, and need to migrate to warmer locations."

And the Midwestern prairie ecosystem was their historic center of breeding, notes Dr. Lincoln Brower. The original prairie covered some 433 million acres and was host to a great diversity of milkweed--about 22 Asclepias (milkweed) species. Ironically, monarchs were probably never very abundant to the east of the prairie, believes Brower. However, plowing of the prairies, together with clearing of the eastern forests, promoted the growth of the common milkweed, Asclepias syriaca, and probably extended the center of the breeding eastward.

A Field Trip to the Prairie with Dr. Lincoln Brower

Dr. Brower

With this history in mind, we visited the prairie with Dr. Lincoln Brower. His own history is as closely tied to monarchs as the monarchs are to the prairie. Dr. Brower has studied the monarch for almost 50 years. Here are audio clips, pictures and an interview about Dr. Brower's observations on a native Minnesota prairie on September 1, 2001:

"I've only been in a prairie situation like this when monarchs were migrating twice in my life and it's so beautiful to see these absolutely mint condition butterflies. They've just hatched out, they're probably 2-3 days old. Their wings are actually almost shining in their brilliance. And I always say to myself, what a beautiful animal this is. I've been studying them now since 1955, that's what, 46 years? And, you know you might think somebody that has studied the same thing for 46 years would be sick of it, but I just never get sick of these creatures. They're just so elegant and beautiful!"

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Dr. Brower on Schaefer prairie, where 245 native plant species can be found.

Sneaking up on a nectaring monarch

"If you try to catch a butterfly between your thumb and forefinger in the summertime you'll have a very, very hard time catching it. But they are so intently nectaring [during migration] that you can actually, if you're really careful, sneak up with your thumb and forefinger and just grab one and then take it in your hand and gently look at it and see whether it's a male or female.

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Comparing male and female monarchs

Note larger abdomen of monarch on the left

"You can look--if they've had a good feed their stomachs will actually be fat. (See photo.) They feed on that [nectar], and the nectar has sugar in it. They convert that sugar into fat and that fat is the energy store that they use to fly down to Texas and then on into Mexico. (That sure beats $2 per gallon gasoline.) Ha, ha, ha...It sure does!"

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