Monarch butterfly deaths on Texas roads could be significantly harming the species’ population, experts say. Texas A&M researchers are working to find out how common this problem is in hopes that improvements can be made to protect the insects.
For two years, researchers will conduct seasonal surveys to find the location and the extent of “roadkill hotspots,” said Robert Coulson, professor in the department of entomology with the Knowledge Engineering Laboratory. The first survey, which started last month and will continue through the end of November, covers the monarch butterfly autumn migration as the insects travel to Mexico. In total, there will be two autumn surveys and two spring surveys throughout the two-year study.
Coulson said the research is a continuation of previous A&M studies that found that road mortality in Texas depleted 4%of the population that would normally get to Mexico. Coulson said that percentage is huge, accounting for millions of insects.
The current research surveys will require A&M field assistants Janice Bovankovich and Kaitlin Lopez from Monarch Joint Venture — an organization that aims to protect the monarch migration across the U.S.— to count the dead butterflies along 100-meter stretches on dozens of Texas roads. The field assistants will be supervised by James Tracey, a postdoctoral research associate in the department of entomology.
The data will be presented to the Texas Department of Transportation so they can consider potential ways to protect the population.
“The population of the insects as they migrate to the overwintering sites in Mexico are at the lowest population levels throughout the entire migration process, and the populations are concentrated as they are going through Texas,” Coulson said. “Any mortality agent that affects the population at that stage is really significant.”
The viable population of monarchs in Mexico during the migration process has fallen by 80% during the past two decades, which Coulson said can have detrimental effects on future generations of the insect. In 2014, protection for monarchs was sought under the federal Endangered Species Act and currently is under review. In December 2020, the U.S. Fish and Wildlife Service will determine if monarchs belong on an endangered or threatened species list. The data A&M researchers collect will be considered in the Fish and Wildlife Service’s decision.
Researchers also collected information about past mitigation efforts that may play a role in what types of solutions will later be put in place to reduce the number of butterfly deaths. However, Coulson said mitigation efforts have only been performed for birds and mammals. Some mitigation strategies, which could potentially be made applicable for butterflies, include putting up signs for people to slow down near areas that are roadkill hotspots or create corridors across roads to help them move through the area safely.
TxDOT will have the final say on what changes, if any, will be enforced on Texas roadways to protect monarch butterflies. Researchers did not make any types of recommendations on which strategy would be best.
“We present what has been done in the past and the Texas Department of Transportation will evaluate what is sensible in terms of implementation in the future,” Coulson said.
According to an AgriLife Today press release, monarchs have the longest migration of any insect. Many travel 3,000 miles from Canada to Mexico in the autumn, and then another 1,0000 miles back to Texas and Oklahoma during the spring to lay eggs. During their autumn journey, the butterflies move through narrowing areas on their migration to Mexico.
While monarchs are present in the Brazos Valley, the main migratory path is farther west of Bryan-College Station. Coulson said the county is on the periphery of the migration pathway, so roadways in the area will not be surveyed.
Coulson said that if anyone has observed large populations of monarchs or been involved in a roadkill incident, to contact him at email@example.com so the team can investigate.