The Eel and the Butterfly

At birth, American eels begin a journey that makes the travels of Odysseus look like a stroll around the block. Departing from seaweed beds in the Sargasso Sea, these mysterious fish swim thousands of miles west, many of them settling in freshwater estuaries along North America’s Atlantic Coast. As frequent MCV contributor Christine Petersen explains in this issue’s Young Naturalists article, some eels even make their way up the Mississippi River to Minnesota, where they’re one of the state’s rarest fishes. Years later, adult eels return to the seaweed nurseries of their youth to breed and complete their improbable life cycle. 

Petersen’s story reminds me of another epic migration. Every autumn, Minnesota’s monarch butterflies flap and glide down to Mexico’s Sierra Madre Mountains, wintering in their favorite tree, the towering oyamel fir, before heading back to the Midwest in the spring. On its way north, this so-called “super generation” of monarchs breeds, then dies off, leaving the kids to continue the journey. It can take up to four generations for the butterflies to return to Minnesota. 

The migratory patterns of eels and monarchs are extraordinary examples of nature’s persistence. Unfortunately, both creatures face a host of threats. As you read this, a garbage patch hundreds of miles across in size is bobbing in the gentle currents of the Sargasso, degrading eel habitat along its path. And if the fish is lucky enough to reach freshwater, it must contend with dams, pollution, and other hazards. Minnesota’s monarchs, meanwhile, have endured extreme habitat loss in their northern and southern homes. 

Despite these challenges, eels and butterflies (and countless other critters) continue to travel ancient migratory routes, nature’s pilgrims compelled forward by genetic wiring. To quote Jeff Goldblum’s quirky Dr. Malcolm in Jurassic Park, “Life, uh, finds a way.”