The monarch butterfly’s distinctive black and orange wings make it one of the most easily recognized butterflies in the sky. To potential predators, that same regal pattern signals the dangerous presence of milkweed, a poisonous plant on which monarch caterpillars feed.
Native to the Americas, the monarch has colonized such far-flung locales as western Europe and Australia. North America’s two main populations of monarchs were believed to be divided by the Rocky Mountains, however, recent studies suggest the two populations may commingle extensively.
The lives of monarch butterflies are marked by yearly migrations that take three to four generations to complete. North America’s western population migrates to California, while the eastern population—which can range as far north as Canada—migrates south, funneling through Texas and hugging the Gulf Coast down into Mexico.
At the terminus of the southern migration in central Mexico, tens of millions of butterflies overwinter at less than 20 sites, gathering in roosts 20-30 million strong. They begin to disperse in late February and early March, mating and then flying north, usually making it to Texas before laying their eggs on milkweed plants. The next generation continues the migration, leapfrogging north until the third or fourth generation arrives as far north as Canada in May and June. This final generation migrates up to 2,200 miles back to Mexico, arriving in early November. They begin migrating individually, and then slowly gather into flocks as they converge upon roosting sites.
Although monarch butterflies aren’t known for their speed, they are able to travel great distances quickly. One tagging program recorded a male monarch flying 265 miles in a single day. As they head south, the butterflies may ride thermals to reach altitudes of 4,000 feet, averaging a stately 12 miles per hour.
Intermediary generations have an adult lifespan of only four to five weeks, but the final annual generation lives up to seven times longer, making the long migration and then surviving to overwinter, mate and return north.
During these migratory periods, monarch butterflies can be found on a variety of Texas locations, including Dolan Falls, Independence Creek and Fred and Loucille Dahmer Caddo Lake preserves.