Searching the sand for the flat-tailed horned lizard

By Kate Miyamoto, Public Affairs Specialist

Zigzagging back and forth, I follow invisible lines on the ground, head down, eyes alert watching for any slight movement. It’s a hot August morning in 2022, and I, along with four other Bureau of Land Management staff are walking a plot of BLM-managed public land in the California desert near El Centro. To the casual passerby, we appear to be searching for a lost earring, pacing the hot sand, hoping for a glint of gold. But it’s not jewelry we seek.  

BLM El Centro Field Office staff are monitoring the flat-tailed horned lizard – a sand-colored, medium-sized, flat-bodied lizard with enlarged pointed scales and eight horns on the back of the head. Its head resembles, in my opinion, a tiny version of a dragon from the popular show, “Game of Thrones.”

The flat-tailed horned lizard is found in the Colorado Desert in California, Arizona, and Mexico. Its California range is mostly in sandy desert washes and flats with sparse vegetation of creosote bush or desert scrub in central Riverside and Imperial counties. Flat-tailed horned lizards mostly eat ants, are adapted for hot dry environments, and rely on camouflage for survival.

The lizard’s habitat and abundance has been reduced due to human activities such as agriculture, development, and recreational use. The species has been federally proposed for listing as threatened under the Endangered Species Act, but in 1997 Federal and state agencies came together to develop a conservation agreement and form the Flat-tailed Horned Lizard Interagency Coordinating Committee. This committee consists of 13 stakeholders from Federal and state agencies committed to conservation of the lizard and its habitat, including the BLM, U.S. Fish and Wildlife Service, California Department of Fish and Wildlife, Department of Parks and Recreation, Arizona Department of Game and Fish and several Department of Defense agencies.

In 2022, the BLM’s El Centro Field Office completed its annual demographic monitoring project for the flat-tailed horned lizard, collecting data such as age, sex, size, and weight and genetic samples. It was the first year the BLM collected genetic samples from the lizards to better understand gene flow, population connectivity, genetic profile, and more. The purpose of the demographic surveys is to gather information on population dynamics that can be used to track local populations over time. The data gathered during the months-long monitoring effort is entered into a database and used by the Flat-tailed Horned Lizard Interagency Coordinating Committee.

Monitoring involves searching for, capturing, and recording data on flat-tailed horned lizards in four permanent plots in three designated management areas in the lizards’ habitat range. Plots are surveyed for 10 days each and involves zig-zagging a nine-hectare plot (300 meters x 300 meters) marked into at least eight lanes to ensure 100% of the plot is surveyed each day.

To avoid the heat, the BLM staff start monitoring around 5:30 a.m. and finish around 10 a.m. before ground temperatures reach about 104° Fahrenheit and lizard activity decreases. When I arrive on the August morning, the air temperature is hovering in the 100s, and four lizards have already been found.

During our search for flat-tailed horned lizards, we see other signs of life, including marks in the sand indicating a sidewinder rattlesnake, a desert iguana, a fringe-toed lizard, and other tracks.

After about an hour of zigzagging in the sand, we hear a shout. A flat-tailed horned lizard has been spotted! We mark our spot in the sand with a flag and make our way towards our colleague. I strain my eyes to see where everyone is pointing, and finally see the lizard perched on a rock looking for an escape route. Flat-tailed horned lizards are quick and can run under low brush or burrow quickly into the sand, so speed is of the essence.

Peter DeJongh, biologist from the El Centro Field Office jumps into action to capture the lizard, and the team records its age, length, weight, sex, and a takes genetic sample from a back claw. If the lizard is large enough, a passive integrated transponder tag is safely injected under the lizard’s skin, much as one would do with a pet, so that the biologists can identify this specific lizard in future surveys. After a few minutes of recording data, the lizard is released and disappears into the sand.

Success! On this August morning, five lizards were found, all of them juveniles, three females and two males.  

The flat-tailed horned lizard annual monitoring project gathers important data used to monitor the status and assess the health of the lizard. In a good year, about 35 lizards are found and in bad years only five. In 2022, 26 lizards were found during six weeks of monitoring and the BLM successfully surveyed two of the plots.

Flat-tailed horned lizard populations have been stable for the past few years, and projects like this one provide insight into the behavior of these populations over time, including changes in abundance and survivability.

It's not every day your office is a plot of sand, and you’re searching for a tiny, camouflaged lizard. But this important field work gathers crucial data used by the BLM and its partners to help manage the flat-tailed horned lizards and their habitat, and ensure they continue to race across the sand