Warm October grounds monarch migration through Hill Country
Monarch butterflies are not migrating in mass numbers through the Texas Hill Country this fall due to higher-than-normal temperatures. Adobe Stock image
October is typically the peak of monarch butterfly migration through the Texas Hill Country, but higher-than-usual temperatures have reportedly restricted the beautiful bug’s normal travel patterns.
Monarchs rely on a drop in mercury and shorter days to trigger their southward migration to Mexico, according to the U.S. Forest Service, but they seem to be avoiding Central Texas due to the warmer fall.
Burnet County, for example, has had daily highs in the low to mid-90s almost every day this month, as of Oct. 15. The average October temperatures for the county range from low 80s early in the month and 70s by mid-month.
Oct. 10-22 is usually peak migration time for monarchs through the Hill Country, but that window seems to be rapidly closing. Local experts are not seeing a normal number of butterflies for this time of year.
“Still no monarchs,” said longtime Central Texas monarch tagger Jenny Singleton in an Oct. 15 article published by the Texas Butterfly Ranch. “We need a cold front so bad—but it doesn’t look to be in the forecast.”
Singleton is right. The National Weather Service shows temperatures remaining in the 90s and high 80s until at least Tuesday, Oct. 21.
TOO HOT TO MOVE
A new study published by The Royal Society shows that consistent heat might change the behavior of monarch butterflies. When exposed to higher temperatures, female butterflies tend to lay their eggs and remain in place rather than move or migrate, and male butterflies seem to have adverse health impacts.
In an interview for Texas Butterfly Ranch, ecology and evolutionary biologist D. Andre Green noted that monarchs are still moving through Texas, just farther west than normal. He saw about 5,000 of the insects roosting in the West Texas town of Bronte.
“It’s been really, really wild,” Green said. “They just haven’t come east. They’re to the west. I’ve never seen a roost that size.”
Green speculated that the cooler temperatures and winds out west led the butterflies away from the Hill Country, which seems to be trapped in a “heat dome.” That climate phenomenon is when warm air is pinned in one location for a prolonged period.
Learn more about the monarch migration and other Texas butterfly news at texasbutterflyranch.com.