Adult Texas horned lizards range in length from three to five inches, excluding their tails. Today, Texas horned lizards are found in the southeastern tip of Arizona and Colorado, southern and eastern New Mexico, most of Kansas and Texas and all of Oklahoma. They are apparently doing well throughout most of their range except in Texas. Unfortunately, the exact cause or causes of the Texas horned lizard decline are not known. There have been numerous theories as to why they have been declining, including as reduced harvester ant populations caused by competing fire ants.
Harvester ants are the preferred food of Texas horned lizards.
Other theories suggest that loss of habitat from urbanization, over-collection for the tourist trade prior to 1977 and increased use of pesticides may be important factors. Although each of these may negatively impact local Texas horned lizard populations, no one cause can account for the state-wide decline in the Texas horned lizard population. Scott Henke and Alan Fedynich received a research grant from the Houston Livestock Show and Rodeo Association to survey Texas horned lizards for malaria in rangeland plant communities of South Texas. Fedynich believes that malaria may be a reasonable explanation for the statewide decline in Texas horned lizards. If they are, we will assess the disease's impact on several important factors that influence productivity in Texas horned lizards.