“This summer, I heard dozens of stories from Karnes County residents about the once abundant (and still beloved) horny toad,” Wall said, recalling her recent experiences.
Horny toads (or Texas horned lizards) are now considered “threatened” in Texas and are listed as a Federal Species of Concern. Although Kenedy was named the “horned lizard capital of Texas” by the Texas legislature in 2001, surveys conducted by Texas Parks and Wildlife and the Kenedy Horned Toad Club have shown a tremendous decline in sightings within the last decade.
What has led to this rapid decline?
According to Wall, Possible reasons include habitat loss, the persistence of fire ants, loss of food (mainly harvester “red” ants) from pesticides, and environmental changes (like drought).
“For my Master’s thesis in biology at Texas Christian University (TCU), along with Dr. Dean Williams, I am studying the horny toads in Karnes County to understand what is causing their decline and how to bring the horny toads back,” Wall said. “This summer, we searched through alleyways, behind schools, abandoned lots, and empty fields for signs of the horny toads. Every time we found harvester ants, we recorded the GPS location of the mound. We also searched for and collected horny toad scat (excrement). Through these searches, we discovered that many areas of suitable habitat (with plenty of harvester ants for food) had no evidence of the horny toads. The absence of food does not seem to be the reason for their absence in these areas.”
Wall explained that a primary question for this project is: Where and how far do these lizards move in small towns?
“We put transmitters on about a dozen horny toads in Kenedy and Karnes City,” Wall said. “These transmitters send a signal to our receiver and allowed us to re-find the tagged lizards each day. By doing this, we can understand how and where they move in the two towns. We also swab every lizard we found to obtain DNA for genetic analysis. I began my fieldwork in Karnes County expecting to be rewarded daily with new lizard samples. However, actually finding the lizards proved more difficult than I had anticipated. Radio tracking and collecting DNA samples were the easy parts!”
This project is more than just an excuse to be outdoors and play with lizards, Wall said. While previous studies focus on large, protected areas, this study seeks to understand how these animals are living in small towns.
“Studying the physical movement of the horny toad through radio tracking will show us how far the animals move each day, the size of their home ranges, and what types of habitat they prefer in town,” Wall said. “Insight into their genetics will show how isolated these lizards are from one another. If we discover that horned lizards in Karnes County have very low genetic diversity compared to other areas in Texas, it would suggest that they are more isolated, which may be contributing to their decline.”
Isolation results from barriers to movement, including roads, buildings, and fences.
“By understanding their movement and genetics within the county, we can shed light on how to increase the abundance and survival of horned lizards in small towns,” Wall said. “For example, if we discover that these lizards have very little genetic diversity, which can lead to long-term population declines, Texas Parks and Wildlife could potentially move some lizards from one area to another to ‘introduce new blood’ and increase the genetic diversity in each area.”
According to Wall, before any management plans can be considered, the data needs to be analyzed. Back in the TCU biology lab, she has begun analyzing the DNA samples and compiling the tracking data. Only time and plenty of lab work will tell what possible course of action might be pursued.
“I especially want to thank the residents of Karnes County, Dr. Wade Phelps, Ryan Darr of Texas Parks and Wildlife, Maggie and Truett Hunt from The 505, and Mr. and Mrs. H. J. Kolinek for their help and hospitality during my research,” Wall said.