The Fort Worth Zoo recently set a new record by releasing 617 Texas horned lizards into the wild at Mason Mountain Wildlife Management Area as part of the zoo’s Texas horned lizard conservation program. This milestone follows years of collaboration between the zoo, Texas Parks and Wildlife Department and Texas Christian University, focusing on the research and conservation of the threatened species.
The partnership began in 2009 when Dean Williams, Ph.D., TCU biology professor and leader of the TCU “Horny Toad Project,” initiated genetic studies to identify distinct populations of Texas horned lizards across the state.
“After collecting DNA samples from hundreds of lizards across Texas and developing genetic markers, we found that there are three distinct populations: one in the western deserts, one in the northern plains and one in the southern plains,” Williams said.
This research helped inform the zoo’s captive breeding and reintroduction efforts,
ensuring that the lizards were released in areas best suited to their survival. The
Fort Worth and Dallas zoos now focus on breeding and releasing individuals from the
northern plains population.
When asked about the biggest challenges in ensuring the survival of the released hatchlings, Williams identified two main issues: high predation rates and invasive fire ants.
“Predation by snakes, particularly coachwhips, and possibly raccoons is a significant problem. The raccoon population has increased in the region due to the presence of deer feeders on surrounding ranches, which likely creates unnatural predation pressure on horned lizards,” Williams said.
Another challenge is fire ants, which not only prey on the hatchlings but also reduce the availability of small native ants, a crucial food source for them. To address these concerns, Williams’ graduate student, Kira Gangbin ’27, is collaborating with the Texas Parks and Wildlife Department and the Fort Worth Zoo to explore targeted fire ant control methods that won’t harm the native ants.
Over the years, nine graduate students and numerous undergraduates have contributed to the Texas horned lizard studies.
“All the study results I talk about were mostly the result of their projects,” Williams said.
Fifteen undergraduates have worked on Texas horned lizard research in Williams’ lab at TCU, generating and analyzing genetic data from both wild and zoo populations, assessing habitat use through photographic analysis and identifying ants and other insects in the lizards’ diet using
DNA barcoding. One current undergraduate is also investigating the parentage of Texas horned lizards by extracting DNA from eggshells found at nest sites.
“We’re exploring whether a clutch of horned lizard eggs, typically 20-30 eggs, comes from a single father or multiple fathers,” Williams said.
Knowing the mating system will help researchers better model the retention of genetic diversity in the reintroduced population.
“For the Texas horned lizard, we need to restore habitat, curb development and reintroduce it to areas where it has disappeared. By moving individuals between isolated populations, we can maintain genetic diversity, which is vital for the species’ long-term survival,” Williams said.
The partnership between TCU, the Fort Worth Zoo and Texas Parks and Wildlife Department continues to drive progress toward ensuring that this iconic species will persist for generations to come.
