It is one of the most amazing migrations in all of the world, not least because the animal making the 3,000-mile journey weighs half a gram and North Texans often see the ancient journey from their back yards and gardens.
But, with only isolated sightings, the last few weeks proved disappointing for monarch butterfly watchers in virtually all of Texas. Normally the butterflies’ migration from the Red River to the Rio Grande Valley is hailed as one of autumn’s great marvels.
“I’ve seen probably four monarchs in the last three weeks,” lamented Michael Warriner, an invertebrate biologist with the Texas Parks & Wildlife Department in Austin.
The likely reason lies in the merciless drought, which dramatically reduced the butterflies’ main food source as they moved south for the winter. The shortage of nectar from blooming plants, plus thousands of acres scorched by wildfires, likely meant that the migratory pattern was dispersed over a much greater area as the butterflies sought food. Based on informal reporting by residents, the overall count appears to be below average.
“The pattern was widespread, all the way from the I-35 corridor to the Davis Mountains,” said Mike Quinn, an entomologist who is coordinator of Texas Monarch Watch, part of a monarch educational and research organization based in Kansas. “They usually aren’t that widely distributed.”
Mysterious and remarkable
The monarch butterfly, like Pacific salmon and the gray whale, makes a jaw-dropping annual migration that must be mysteriously plugged into its genetic makeup, made all the more remarkable because no single monarch makes the entire round-trip journey. Their offspring and their offspring’s offspring know what to do and where to go on their own.
The monarch has an outsize reputation among nature lovers in the Plains states.
Grapevine, for example, has an annual festival — the Butterfly Flutterby — to celebrate the migration.
“They have this mystique,” Warriner said. “They’re easily identifiable, they’re pretty, they don’t sting, they’re interesting and there’s that migration. Popular interest has just built up.”
Most of the insects begin in the upper Midwest and Great Lakes region in August and September, flying on thermals and fronts across North America to spend the winter in a compact mountainous area of central Mexico’s Michoacan state. They usually move through Texas during October, fattening up along the way on the nectar of flowers, trees and virtually anything else that blooms.
“Doing a cross-continental marathon, they are actually gaining weight, which is counterintuitive,” Quinn said. “By the time they reach their over-winter grounds in Mexico, they are supposed to have their highest fat content, which they essentially live off of during the winter.”
A depressing sight
But Quinn said he drove through the Hill Country last month and was disappointed in how many dead plants and how few butterflies he saw.
“The drought really appears to have had profound effects on the flora,” he said. “The juniper is dying in wide patches, and that’s one of the last trees I would have thought would be impacted. Walking along riverbeds, there were almost no nectar sources. That suggests the monarchs would be pretty stressed coming through Texas.”
Researchers and professors will get a better count of the monarchs once they arrive in their winter grounds in Mexico in a few weeks. That will also allow researchers to gauge their weight, which will in part determine how they fare in the cold.
Especially harsh winters have led to significant die-offs within the colony, but they have typically happened in years when the population was robust. This winter, researchers are hoping for mild temperatures so that a major loss doesn’t coincide with a below-average count.
“The long-term trend over the last 15 years is downward,” Quinn said. “Every year, there are, on average, fewer in Mexico. We’re getting closer to that point when we’ll have a die-off in a low-numbers year, which would really be an unfortunate situation. We’ll know more in the spring when we see them coming back.”