Graduate student Kelly Nail was pleasantly surprised at the bounty of butterfly life unfolding at the Museum Reach milkweed patch on the San Antonio River Walk just this week. The patch of milkweed, a Monarch butterfly host plant, was planted two years ago as part of the City’s redevelopment of the former drainage ditch and lies just a five-minute walk south of the Pearl development on lower Broadway.
Nail majored in mathematics and biology at St. Olaf College. After teaching high school biology in rural Mississippi, she returned to school to study Monarch butterflies. Her dissertation, overseen by renown Monarch butterfly scientist Dr. Karen Oberhauser at the University of Minnesota, will explore the effect of climate change on Monarch butterflies. Nail flew to Houston this week to talk to Monarch citizen scientists about “winter Monarchs,” then made the three-hour drive to San Antonio to see how Alamo City butterflies are faring.
The Museum Reach milkweed patch did not disappoint.
We observed several Monarchs flying, more than a dozen Monarch caterpillars and one Queen caterpillar in various stages of development, dozens of chrysalises–spent, interupted, and in process–and one egg. We also saw instances of the brilliant-but-creepy tachinid fly. This parasitoid lays eggs on Monarch caterpillars, which kills them when the flies feed on their living bodies and eventually hatching just before the Monarchs pupate, leaving a caterpillar corpse in their wake. Scientists suspect that Monarchs born later in the season and further south are more likely to encounter such a fate.
Nail was delighted to find such a jackpot of Monarch data. “I was impressed to see all stages of the life cycle in one single place,” said Nail. “And right along the River Walk in the middle of San Antonio. It’s pretty amazing.”
One of the questions she hopes to answer: Are “winter Monarchs” reproductive? Judging from this field trip–no doubt about it.
Butterfly fans and those of us who tag Monarch butterflies in the fall have always been told that late season Monarchs do not reproduce and are behaviorally and biologically different from spring and summer Monarchs. Supposedly, late season Monarchs remain sexually inactive, saving their energy for the great migration to Mexico. There, they wait out the winter and emerge from their diapause in the spring to partake in an orgy of butterfly mating in the mountains of Michoacan, often laying their first eggs on Texas milkweeds in March or April.
Butterfly fans know that local populations of Monarch butterflies can establish themselves when host and nectar plants are available and the weather cooperates. We see it in Houston, Florida, and now–San Antonio.
Based on personal observation and discussions with professional butterfly breeders, it appears that Monarchs are just like us: opportunists. With ripe conditions and mates available, they’ll pounce on the chance to reproduce.
Our local Monarchs are likely to continue their procreative antics as long as temperatures remain above freezing and milkweed and nectar plants provide host and sustenance. San Antonio’s Museum Reach milkweed patch, semi-protected from the elements with supplementary grey water and temperatures more moderate than street level, is destined to become a favored nectar and host plant hangout where Monarch butterflies gather to find partners. That’s good news for those of us who hope to enjoy butterflies year-round.
We look forward to Nail’s research and to more visits to the milkweed patch.Like what you’re reading? Don’t miss a single post from the Texas Butterfly Ranch. Sign up for email delivery in the right navigation bar on this page, like us on Facebook, or follow us on Twitter, @butterflybeat.