Conditions are ideal for Monarch butterflies in Texas this fall, but a freak spring ice storm at their ancestral roost in Mexico has migration forecasters calling for a setback in their population numbers.
On March 8, ice, snow and dramatic winds ripped through the Oyamel forest where the Monarchs roost each winter. Just as they were heading north to lay the first generation of eggs in Texas, the storm destroyed 135 acres of forest and killed an estimated 6.2 million butterflies – about 7.4% of the 84 million roosting at that particular preserve, Mexico's Attorney General for Environmental Protection Alejandro Del Mazo recently told the Associated Press.
The severe squall set the 2016 season off to a bad start and will likely result in a setback to the threefold population increase the Monarchs enjoyed last year, scientists suggest.
Mother Nature's deadly blow hit especially hard here in San Antonio, the nation's first Monarch Butterfly Champion City, so named by the National Wildlife Federation (NWF). In the past year, here and elsewhere, the migrating orange-and-black insects have never enjoyed more fame and fortune, as government and educational institutions have increased pollinator habitat, earmarked millions for research on milkweed – the insects' host plant – and raised public awareness of Monarchs and other pollinators to unprecedented heights.
“I know how much we all look forward to seeing the majestic Monarchs every year, and it saddens me to think that their population has been impacted so dramatically by the ice storm in Mexico," said Mayor Ivy Taylor, who signed the NWF's Mayor's Monarch Pledge on Dec. 9 last year. "However, we will keep working to provide them with a safe haven here in San Antonio.”
Chip Taylor, Ph.D., founder of Monarch Watch, predicted in his annual summer Monarch Population Status blog post that 2016 would likely be comparable to 2014. The last three years have been closely monitored by Monarch aficionados: In 2013, the population dropped to 33.5 million butterflies, the lowest since records have been kept; in 2014, it increased to 56.5 million; and last year 200.5 million butterflies were recorded.
In 2015, President Obama released a National Pollinator Strategy that set out to increase the Monarch population to 225 million – the historic 20-year average.
The iconic insects make one of the most remarkable annual migrations on the planet, traveling up to 2,800 miles from Mexico through the United States to Canada and back over multiple generations.
Their journey starts in March, where they spend the winter in the Oyamel fir forests. After a cue from the sun, they head to Texas where they lay their first generation of eggs on milkweed plants – the only plant they use to breed. Those eggs hatch into caterpillars who then grow into butterflies that continue the cycle over the summer, with fourth or fifth generation butterflies returning to Mexico in the fall to overwinter, despite never having been to the specific roosting site where their ancestors launched the journey. The following spring, those butterflies begin the cycle anew.
Glum predictions aside, conditions could not be more perfect in Texas to welcome the migrating butterflies this fall.
Each year around Labor Day we see the first trickle of Monarchs, or what's called the 'pre-migration migration' – a vanguard of reproductive Monarch butterflies that lay eggs which will hatch and become the final generation of migrating adults.
This weekend, half a dozen adult Monarch butterflies showed up right on cue along the Llano River in the Texas Hill Country. Even more interesting, dozens of caterpillars and eggs were spotted on the Swamp milkweed, Asclepias incarnata, a Monarch butterfly host plant, and suggested that Monarchs had been passing through in the preceding weeks. Three late stage caterpillars literally hung out on the Llano, preparing to bust their stripes and go chrysalis.
Goldenrod, Purple mistflower, White boneset, Snow-on-the-prairie, all late season nectar plants that the butterflies use as nectar stops, exhibited their showy sprays along the Llano River and elsewhere in the Texas Hill Country this weekend. Bees, wasps, moths, beetles, and aphids were seen in large numbers, following a series of rain events that followed a scorching South Texas summer.
All those late season nectar plants are good news for the Monarchs that will pass through here in larger numbers starting in early October.
A quick survey of local Monarch Watchers had few sightings to report.
"Nothing to report in Comfort yet," said Monarch Watch Education Outreach Specialist Cathy Downs. Monarch Larvae Monitoring Project volunteer Mary Kennedy said the same thing. Master Naturalist Drake White, who manages the Phil Hardberger Park butterfly garden and runs the Nectar Bar, a Facebook page devoted to helping people raise butterflies, reported two Monarch sightings. Local botanist and landscaper Charles Bartlett of Greenhaven Industries reported seeing one Monarch locally.
Sightings throughout the spring and summer have been slim, with the freak sleet storm taking most of the blame for the Monarchs' absence.
"We really miss seeing and raising the Monarchs. ... It is quite distressing to think how badly the population must have have (been) hit with the storm earlier this year. Last year we raised 200 Monarchs," wrote Tony Kowall of Park Ridge, Ill. on June 20 to the DPLEX list, an email list that reaches about 800 Monarch butterfly enthusiasts, scientists, and citizen scientists across the nation.
Kowall lives in the prime Monarch breeding ground in the Midwest where population recoveries can happen – or not – depending on the weathe and other factors since that's where the butterflies reproduce.
Folks posting on Facebook echoed the dearth of Monarchs this summer.
"I still haven't seen any Monarch butterflies yet. My common milkweed has grown six feet tall. Still no butterflies. I'm concerned. They should have been here a while ago," Teresa Bailey, who lives north of Kansas City, Miss., posted June 14 on Facebook.
We will know soon enough how big the population this year will be. Based on San Antonio's latitude of 29 degrees, peak Monarch migration should occur in late October, sometime between Oct. 10-22.
Top image: Monarch butterflies were at the center of the three-day Monarch Butterfly Fest at the San Antonio Zoo in March. Photo by Kathryn Boyd-Batstone