Abundant rains during the monarch butterflies’ primary breeding season in the Midwest followed by severe heat and drought appear to be limiting the number of migrating monarchs that will be moving through the Texas Funnel on their way to Mexico this fall.

The good news? Any monarchs that make it to Texas will enjoy the fruits of a relatively mild and wet summer that has spawned a bounty of late season nectar.

A trip to the ranch this week had the feeling of spring: lush green foliage, abundant wildflowers, a roaring Llano River, and insects galore–although few monarch butterflies. Queens and Red Admirals were prolific and we witnessed several courtship flights. Grasshoppers flushed from the tall grasses along the river and the cicada chorus was deafening each evening.

Is this spring–or fall? Plenty of nectar and other insects along the Llano River in the Texas Funnel for any arriving monarchs. Video by Monika Maeckle

Swamp milkweed, Ascelpias incarnata, lined the Llano River banks. Very few monarch butterflies were evident, but we witnessed several late stage monarch caterpillars, and eggs were evident–whether they were Queens or monarchs is difficult to say.

Typically, we enjoy what Monarch Watch founder Chip Taylor calls the annual “pre migration migration” around Labor Day. That didn’t happen this year.

“None,” said Jenny Singleton, when asked if she’d seen any of the iconic insects.

Singleton has been tagging monarchs in the Texas Hill Country at her ranch near Hext as well as in North Texas as chief docent of the Grapevine Butterfly Flutterby Festival for decades. She, like others, categorized 2024 as “a weird year.”

Scientists have expressed concern.

“The take-home message is that I’m concerned,” said Karen Oberhauser, longtime monarch butterfly biologist and professor emeritus at the University of Wisconsin at Madison.

“We needed a good year to make up for the low numbers last winter, ” she said, referencing the 59% decline of 2023’s migrating monarch butterfly population. “It doesn’t look like we got it. Hopefully lots of those that are flying south will survive the migration,” she said.

Wendy Caldwell, Executive Director for Monarch Joint Venture, a monarch butterfly and pollinator conservation organization, told CBS News this week that “it seems like the numbers have been down.” She added that climate change plays a role in the decreasing monarch counts, since the butterflies rely on resources being available when they arrive. In short, monarchs need hospitable temperatures, nectar and host plants to be present when they show up.

“As that becomes less consistent and less predictable, that has an ability to really affect the way the population can reproduce,” said Caldwell.

Kristen Baum, director of Monarch Watch, at the University of Kansas at Lawrence, called 2024 “interesting.”

“We started the year with low expectations based on the size of the overwintering population being the second lowest on record.  Then, reports were better than expected coming out of Texas, with hopes for a strong first generation.  However, with recent observations from the Midwest, we are back to low expectations for the fall migration.  We will know more in the coming weeks,” she said.

The monarch population on the West Coast also seems infected with the same strangeness. “I am a little concerned,” said David James, a monarch biologist at Washington State University. James said that up until early August, monarch sightings were very good–about 75% greater than the same time last year. Then around the middle of August, the sightings stopped.

James speculated that that the natural enemy community–monarch predators–had a good summer and caused greater than normal mortality to eggs and larvae.

That people are seeing fewer monarchs is an observation supported by reports from members of the D-PLEX, a monarch butterfly-centric email listserv operated by Monarch Watch.

Diane Levesque, a longtime citizen scientist and monarch tagger in Enid, Oklahoma, monitored a stretch of highway for two hours on September 4. “There was lots of milkweed, goldenrod and other blooming things but butterflies were scarce and monarchs almost non-existent,” she shared on the email list.

Another monarch watcher, Don Davis, reported from Point Pelee National Park in Ontario that as of September 5, “monarch sightings in the park are few and far between.”

Llano River

Weird: Llano River September 5, 2023/ Llano River September 6, 2024 –Photos by Monika Maeckle

In an August 20 Monarch Population Status report posted on the Monarch Watch blog, Chip Taylor, professor emeritus at the University of Kansas at Lawrence and founder of the organization, pointed to  abundant rains in the Midwest during monarch egg-laying season, and how rain can impact a female’s inclination to lay eggs.

‘Rainfall, if it persists for days – and it did over wide areas – can make a difference by limiting the number of hours and days during which females can lay eggs,” he wrote.

“If it’s cloudy and rainy they don’t go out and lay eggs,” he said.

Taylor also cited the “significantly higher-than-average September temperatures” that have occurred in 17 of the last 30 years. In 13 of those years, the population has decreased from that of the previous year, and all indications suggest 2024 will become the hottest summer in history–not good for monarch butterflies.

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High temperatures delay migrations, burn the fats that the monarchs are trying to store to get them through the winter at the roosting sites, and limit reproduction, Taylor said. “They don’t even fly when temps are in the 90s, because they overheat,” he said, adding “They only have so many wingbeats.”

How the final tally will impact the upcoming US Fish and Wildlife’s decision to consider monarchs worthy of protection under the Endangered Species Act remains to be seen. An updated decision is expected by the end of this year.

TOP PHOTO: Swamp milkweed hosts a fifth star instar monarch butterfly caterpillar.–Photo by Monika Maeckle

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