Watch: Monarch Butterflies Get Tiny Radio Trackers

While monarch butterflies may be relatively small in size, they make one of the most epic journeys known to animal-kind. During the spring, the first generation of butterflies leaves its winter home in Mexico or California to head north. Each successive generation flies even farther north, ending with the fourth generation finally making it to its summer destination in the northern United States or Canada. When the time comes to head south again for the winter, the fourth generation makes the entire journey back by itself, returning to almost exactly the same spot from which the first generation took off, even though the fourth generation has never been to that location before and there are no earlier surviving generations around to show the way.

Just how monarchs make such a phenomenal 5,000-mile round-trip migration is what ecologist and National Geographic Emerging Explorer Martin Wikelski is trying to understand. “The monarchs' migration is really like in the old days when settlers went west. How do they know where to go, and when do they decide, Oh, I'm now the fourth generation. I go south, it's winter? What is that?" Wikelski asks in wonderment, then postures some theories: "The last generation probably measures day length. It realizes that the days are getting shorter, maybe also the temperature gets colder, and then they realize it's time to go south. But we also think it's probably swarm intelligence, because they see each other and then they join the crowd and go south."

A few years back Wikelski, along with monarch butterfly expert Chip Taylor, successfully placed electronic tags on free-flying, migrating monarch butterflies for the first time. While Wikelski hopes that tracking the butterflies will lend more insight into how monarchs pull off such an incredible journey, he's also interested in discovering the various habitats that the butterflies call home along the way.

"Butterflies are endangered. The problem is that they have only few habitat places. If those areas are destroyed, then there are no monarch butterflies anymore. They move all year and we see them at some point, but then they're gone and we don't know where they go." By having a better grasp on where the monarchs travel, Wikelski and conservationists can advocate to protect the butterflies' habitats and hopefully help the species bounce back.

Saving a species from extinction is more than enough reason to carry out his work, but as Wikelski points out, humans need butterflies too. "Butterflies are part of our pollinators, and most of what we eat depends on pollinators. Pollinators have an ecosystem service value of billions of dollars every year. If we start losing them, then this is really dangerous."

Almost as amazing as the monarchs' migration is the technology Wikelski has helped develop to track the species' journey. Check out the video to see how Wikelski and Taylor apply the electronic tags (which weigh about .007 of an ounce) to the delicate creatures and how the scientists then track the butterflies.

Being able to tag and follow the butterflies is nothing short of incredible. "The best moment was when the first butterfly with the tag took off and landed on a flower and foraged, and then really flew with the tag. Initially it is a little hard because they have a little weight that they have to get adjusted to, but then when they fly off, it's like a launch of a satellite," Wikelski says. "It's so amazing because we didn't know if it would work, and now we know that they fly with the tag and we can follow them, so this is really an amazing advancement in science and understanding of these insects."

Learn more about Wikelski's work tracking animals in his National Geographic Explorer's bio and National Geographic Adventurer of the Year page.

Check out other episodes from the Expedition Raw series to see more moments from National Geographic explorers in the field.

PRODUCER: Nora Rappaport
EDITORS: Nora Rappaport and Dmitry Torgovitsky
SERIES PRODUCERS: Chris Mattle and Jennifer Shoemaker
GRAPHICS: Chris Mattle and Babak Shahbodaghloo