In Search of a Vanishing Lizard
Several years ago, Nature Conservancy vertebrate zoologist Mike Duran was concerned. In his seven years of conservation work, he’d never once seen a spot-tailed earless lizard (Holbrookia lacerata). The northern subspecies, or H.l. lacerata, historically occurs above the Balcones Escarpment, the fault line that separates the Edwards Plateau from the Tamaulipan Thornscrub ecoregion of southern Texas. The southern subspecies, or H.l. subcaudalis, has dwelled traditionally below that fault line. But in modern times, finding either type of the lizard—which measures four-and-a-half to six inches long and has no external ear openings—has proven difficult, if not impossible.
“Right now, we just don’t know where the spot-tailed earless lizard still occurs and where it has probably been extirpated,” or locally extinct, Duran said in 2009. “That’s what we have to start with. It all starts with gathering more data.”
To gather that data, Duran teamed up with Dr. Ralph Axtell of Southern Illinois University at Edwardsville, the foremost expert on spot-tailed earless lizards. Together they embarked on four years of field surveys and solicited a lot of help from the public along the way, encouraging amateur herpetologists and outdoor enthusiasts to report suspected sightings. Axtell and Duran—with the help of Dr. Toby Hibbitts of Texas A&M University, Dr. Travis LaDuc from University of Texas at Austin, Dr. Michael Forstner of Texas State University and the late Dr. Andy Price, herpetologist for the Texas Parks and Wildlife Department—ultimately confirmed populations of the northern subspecies in 12 Texas counties. But, after visiting every known historical locality for the southern subspecies, they couldn’t find a single subcaudalis specimen.
“At the time, I was disheartened that we didn’t observe any of the southern subspecies, but I remained optimistic that the lizard still occurred in scattered patches of suitable habitat in southern Texas,” Duran said.
Then a single act of citizen science turned everything upside down. Greg Worley, a mechanic at Laughlin Air Force Base near Del Rio, Texas, snapped a photo of a lizard he couldn’t identify and sent it to the Texas Parks and Wildlife Department. TPWD’s horned lizard specialist, Lee Ann Linum, recognized it as a spot-tailed earless lizard and forwarded the image to Duran, who was “excited and relieved to see evidence that the lizard still occurs in southern Texas.”
In March, he made the trip to Laughlin, where he met up with Danny Yandell, Laughlin’s natural resource specialist. “[We] had not driven 200 meters into the suspected habitat when we observed not one, but six of the lizards scurrying about,” Duran said. As the lizards scattered, he saw several dive into ground squirrel burrows, an action that ultimately “deserves more study.” Before now, there had never been a single recorded observation of spot-tailed earless lizards using mammal burrows for shelter. “Very little is known about the ecology of this species,” Duran added.
For years, herpetologists have believed the subcaudalis was extirpated from its historical habitat in Bee, Refugio, San Patricio, Nueces, Kleberg, Karnes, Live Oak and Atascosa counties. The reasons varied from habitat loss, pesticide use and red fire ants to the invasion of non-native grasses. The landscape at Laughlin however, while not pristine, harkens back to what southern Texas grasslands once were.
“The habitat at Laughlin has been accidentally preserved—they don’t graze livestock or plant row crops and they mow the area frequently to discourage birds, which can’t coexist with jet turbines too well,” Duran said.
Duran and Yandell captured one male lizard in March, the first time a specimen of subcaudalis has been collected in 20 years. On two subsequent visits they collected two more lizards; soon after, Duran donated all three to the Fort Worth Zoo, which has been preparing a captive breeding program for spot-tailed earless lizards (though staffers never expected to acquire this subspecies).
This historic find will go down in the record books as the first recorded sighting of the subcaudalis subspecies in Val Verde County. And after years of surveying Texas in vain for the elusive spot-tailed earless lizard, Mike Duran can move on to his next scientific adventure.
Photo: Spot-tailed Earless Lizard © Mike Duran/The Nature Conservancy in Texas
(this story was originally featured on www.nature.org/texas)