Unraveling the Monarch Mysteries of Deep South Texas

Deep South Texas is nestled along the mighty Rio Grande River that leads to the sandy shores of South Padre Island. Deep South Texas, also known as the Lower Rio Grande Valley of Texas (LRGV), is often considered a mecca for birders due to its avian diversity of tropical resident species coupled with its strategic placement in the center of the Central Flyway for migratory bird species. While the skies are filled with our feathered friends, they are also very much alive with the Fall migration of the migratory monarch butterfly.

Texas has two flyways that are crucial paths for the eastern monarch population’s successful arrival at their wintering grounds in Mexico. The Central Flyway embraces the state’s mid-section, from the uppermost prairies and lakes, through the Hill Country, and dips into South Texas. The Coastal Flyway embraces the coastal region of Texas along the Gulf Coast.

Monarch Partnerships in Deep South Texas

With the documented decline of the migratory monarchs over the past two decades, there has been a need to better understand the role of Texas during the Fall and Spring monarch migrations. Hence, monarch conservation scientists are partnering with citizen scientists to gather data to document and study the monarchs arriving in Deep South Texas, the availability of native milkweed during the Spring, and the availability of nectar plants in the Fall.

Three people wearing dark green shirts that say "Monarch Stewards" look at a clipboard.
NWF citizen scientists collecting data on South Padre Island. Credit: NWF

Monarch scientists from the National Wildlife Federation (NWF) partnered with a local boots-on-the-ground group, the Rio Grande Valley Pollinator Project (RGVPP). The RGVPP was established by local volunteers who encountered a challenge locating where the monarchs would find sustainable, native habitats along Deep South Texas.

The common mission of both organizations is to increase native habitats in Deep South Texas to support the monarch butterfly and other pollinators. The RGVPP was aware of reported monarch sightings well past the Fall migration period, suggesting a possible overwintering population. Partnering with NWF was a terrific opportunity to document these reports and set the wheels of motion into high gear; once supplies such as microscopes and nets were provided by NWF, the business of data collection began in December 2023.

A person wearing a cap looks into a microscope.
A NWF citizen scientist checks for potential Ophryocystis elektroscirrha spores on a monarch’s scales sample. Credit: NWF

Citizen Scientists Collect Migratory Monarch Data

We also agreed to start testing monarchs for the Ophryocystis elektroscirrha (OE) parasite, known to prevail in non-migratory monarchs. The monarch and larvae data collected included monarch sightings, number of monarchs, sex, behavior, testing for OE, and other pertinent information. Monarch habitat data includes native milkweed presence and density, monarch density per milkweed, and adult monarch presence per site. All data collected since 2022 is now in a digital database.

While we need to continue collecting data in the future years to contribute to the production of interesting research analyses, the fieldwork and the very first outcomes are fascinating and inspiring. Our interest has multiplied, and we are now committed to continuing this data collection annually, during the Fall and Spring migrations, in six sites along Deep South Texas.

Among the outcomes of the Spring 2024 data collection, less than 10% of monarchs sampled were infected with OE, and most late Spring migratory monarchs arrived at the LRGV looking faded but ready to lay eggs in healthy, blooming Zizotes milkweed plants—one of our most abundant native milkweeds in the region.

A small green plant with small flower buds rests in a garden bed.
Zizotes milkweed. Credit: Charmaine Richardson/Lady Bird Johnson Wildflower Center 2018

Monarch Stewards Certification Program

NWF will continue to host training sessions, as part of their Monarch Stewards Certification Program. The latest Monarch Citizen Science workshop, hosted in March of 2024, trained 36 LRGV residents to help educate those interested in monarch conservation and recruit more citizen scientists to help uncover the monarch mysteries of Deep South Texas.

How you can continue helping monarchs in your Texas community:

  • Become a Monarch Steward and collaborate with the Monarch Citizen Science Team.
  • Plant a native garden by selecting a diverse palette of native plants that will flower throughout the year.
  • Include one or two native milkweeds in your native garden.
  • Certify your garden as a Certified Wildlife Habitat with NWF.

Edits by Rebeca Quiñonez-Piñón & David Mizejewski, National Wildlife Federation

We thank Disney Conservation Fund for funding the collaborative Monarch Citizen Science Project in Deep South Texas, 2022-2024.