programs Natural Resources

Rio Grande Cooter

(Pseudemys gorzugi)

Background

Although the historic range of the Rio Grande cooter covers thousands of square miles in the United States and Mexico, it is one of the least studied turtles in North America. Biologists did not widely accept the taxonomy until 2007. Basic information about its diet, breeding and habitat needs is still relatively unknown.

Based on information provided in a 2012 petition, the U.S. Fish and Wildlife Service (FWS) decided to review the species’ status in 2015. At the time, biologists believed the Texas population was not reproducing, and dams, reduced water quality, the private pet trade and recreational shooting had extirpated the species from most of the historic habitat. The FWS plans to make a final listing decision between 2021 and 2023 as to whether the species should be protected by the Endangered Species Act.

Research Description

To fill in the knowledge gaps, the Texas Comptroller of Public Accounts contracted with the University of Texas Rio Grande Valley in 2018 to combine new and traditional survey methodologies to determine the presence, persistence, habitat status and habitat associations of the species across its range in Texas.

Starting in the Rio Grande Valley and working up the Rio Grande and Pecos rivers, researchers are using drones, environmental DNA samples, live traps, high-powered cameras and hand captures to document known populations and to search for new ones. Researchers will compare the effectiveness of the various survey methodologies to provide future biologists with tools to effectively find and monitor populations.

Researchers will combine these survey results with high-resolution ground and satellite imagery to document the habitat types the turtle uses. The analysis will document known habitat and estimate likely and potential habitats across Texas.

The researchers have already documented robust populations in unexpected places such as the invasive cane along the banks of the Rio Grande, a cement-lined ditch in Eagle Pass and the water hazards of a golf course.

Deliverables Due by Contract End on Dec. 31, 2019

  • Data from all surveys, including GPS coordinates for each turtle
  • Report and analysis of surveys’ results to estimate:
    • presence, persistence, health and size of populations surveyed
    • habitat associations and status of those habitats range-wide

Why This Research Matters

The Rio Grande cooter depends on a watershed that drains the largest oilfield in Texas and supplies water to the fast-growing cities of the Rio Grande Valley. In between the Valley and the oilfield are two international and federally operated dams and some of the most productive and valuable agricultural land in Texas. Because it is not clearly understood if, how or why the species is endangered, an endangered or threatened listing by the FWS could add regulatory hurdles and uncertainty about permits for projects ranging from new bridge construction for access to oil fields to planning for the water needs of grapefruit orchards and cities in the Valley. Because of its broad range, learning how to protect the Rio Grande cooter may help protect ecosystems throughout the Rio Grande Basin.