SHEILA BRUMMER, BYLINE: At DeSoto Bend National Wildlife Refuge (ph) in western Iowa, everyone in the Ivey-Caldwell family chases butterflies.
LAURIE IVEY-CALDWELL: He's going to land way up high.
BRUMMER: There's mother Laurie...
JULIAN IVEY-CALDWELL: Coming your way - up above.
BRUMMER: ...Father Julian and their two sons - 11-year-old Eli and 10-year-old Irvin.
IRVIN: I really love butterflies. I loved them since I was little, and I love catching them.
BRUMMER: They scamper through the wilderness of a warm Saturday in September, with nets popping out over tall wildflowers through brush and trees.
J IVEY-CALDWELL: I think it's pretty amazing that you've got adults out chasing butterflies.
PETER REA: And if you want to - do you want to just grab it like that - just very gently - just like that? OK.
BRUMMER: Park ranger Peter Rea oversees several late summer outings where volunteers carefully catch...
(SOUNDBITE OF BUTTERFLY FLAPPING)
BRUMMER: ...And mark each monarch with a tiny sticker before letting them go.
REA: There it goes. Adios (laughter).
UNIDENTIFIED PERSON #1: Nice. Good job.
BRUMMER: The goal at the refuge is to tag 300 butterflies this season for researchers to try and follow their path. People who find the tagged insects can enter information with Monarch Watch online. Every creature counts since only about 1% are ever recorded dead or alive in Mexico.
REA: And they're not flying with any other butterfly that has done it. It's a amazing migration.
BRUMMER: Ranger Rea says a migration of hundreds or thousands of miles. Chip Taylor launched Monarch Watch at the University of Kansas in 1992 to monitor migration east of the Rockies.
CHIP TAYLOR: There's something about a monarch that seems to capture the feelings of people.
BRUMMER: He wanted to know more.
TAYLOR: We knew that the monarchs first reached the overwintering sites in Mexico almost on the same day every year. And how is that possible? So we came up with the idea that maybe this is all synchronized with celestial changes, and it turns out that it is.
BRUMMER: Through the tagging of more than 2 million butterflies spanning more than 30 years, scientists uncovered more details. A majority come from the Midwest. And size matters.
TAYLOR: You don't want to be a small pipsqueak here because you don't have the glide power.
BRUMMER: Taylor says monarch butterfly numbers soared before wide herbicide use, and the loss of habitat created a dramatic fall in the '90s. He's seen lower but steady populations during the past decade.
TAYLOR: Monarchs will always be with us, but we could easily lose this migration unless climate change is abated in some way.
BRUMMER: Taylor says drought affects the food supply. Hot temperatures can also impact breeding and slow the butterflies down, making it difficult sometimes for them to reach Mexico in time. The focus now is to tag those still around.
L IVEY-CALDWELL: Goodness gracious. This is not as easy as it looks.
BRUMMER: From veterans to those like the Ivey-Caldwell family, who are just learning about the flightful (ph) creatures, trying to catch a moving target can be difficult.
L IVEY-CALDWELL: These butterflies fly high and fast.
J IVEY-CALDWELL: They're crafty.
L IVEY-CALDWELL: They're very crafty.
IRVIN: Yeah, very crafty.
BRUMMER: They bagged almost a dozen, if you count the one that got away. And Irvin picked up a few pointers.
IRVIN: I learned how to tell a male and female apart. There's dots on the male's wings and none on the female's.
BRUMMER: It's that type of hands-on experience that thrills Chip Taylor, who, at the age of 86, plans a metamorphosis of his own. After volunteering all of these years, he will soon step down as director of Monarch Watch. He set up an endowment to ensure advocacy and appreciation of monarchs lives on.
L IVEY-CALDWELL: I did. I caught one.
J IVEY-CALDWELL: (Laughter).
BRUMMER: For NPR News, I'm Sheila Brummer, near Missouri Valley, Iowa.
(SOUNDBITE OF MARIAH CAREY SONG, "BUTTERFLY") Transcript provided by NPR, Copyright NPR.
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