Texas Parks & Wildlife Magazine   


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The Comeback Kid

Once plentiful pocket pets, ‘horny toads’ are being reared in zoos to release in the wild.

By Louie Bond

Like a miniature triceratops, the diminutive Texas horned lizard was the perfect pocket pet of Grandpa’s era, though he called the wild but gentle creatures “horny toads.” Ask anyone of Grandpa’s era about these little reptiles with pancake- shaped bellies, and they’ll lament the horny toad’s disappearance.

“When I was a kid, I’d catch one and keep it in a shoebox at home,” these older Texans confess regularly to biologists. “I feel pretty guilty about it now that they’re gone.”

Horned lizards are not yet an endangered species, but it’s true that they’re not as plentiful in some areas where they once thrived, and they are threatened by loss of habitat. Help for one of Texas’ most iconic and beloved creatures is on the way with new breed-and-release programs involving zoos, private landowners, conservation groups and the Texas Parks and Wildlife Department.

Nearly 140 2-week-old hatchlings raised at the Fort Worth Zoo and Dallas Zoo were released at Mason Mountain Wildlife Management Area west of Llano in mid-September. Close to 2 million viewers watched a video of the event posted on social media. The San Antonio Zoo hopes to release even larger numbers of slightly older horned lizards this spring.


Texans love their horned lizards, but the creatures have been in decline the past few decades.

Beloved, Iconic, Adorable

Why do we love horned lizards? Is it that charmingly fierce face topped by tiny dinosaur spikes or those improbably squatty legs that barely propel their impossibly round bodies? Is it that they look so ferocious but intend us no harm (they don’t bite or sting)? Whatever the reason, folks have been fascinated by them for generations.

“To know them is to love them,” proclaims Andy Gluesenkamp, conservation director at the San Antonio Zoo, where he heads up a fledgling horned lizard breeding program. “They’re cool looking, they’re easy to catch, and many times, they’re locally abundant. It’s one of those species that seems pre-programmed for people to love.”

Horned lizards, the official Texas state reptile and mascot of Texas Christian University, are as fascinating as they are adorable, with unique defense mechanisms. If alarmed, these little “dragons” can puff up their bodies, pretending to be huge.

If that doesn’t scare off the attacker, a horned lizard can shoot a stream of blood out of its eyelid, blood that tastes very bad to canid predators (coyotes and foxes). Their tiny spikes aid in camouflage and make them more difficult for predators to handle.

“I joke that Texans love horned lizards as much as they hate all other reptiles,” Gluesenkamp says. “Your average Texan is not a fan of snakes and lizards. The horned lizard? That’s a whole ’nother thing.”

But there’s a generational gap in familiarity with horned lizards, he cautions. Some species seem to disappear from the planet with little attention as we become inured to increasing extinctions. While today’s grandparents enjoyed interactions with horny toads, their grandchildren may have never seen one in the wild.

That’s why these individuals and groups are putting so much effort into raising baby horned lizards and releasing them into appropriate habitats to live and reproduce naturally in the wild.

“We want people to encounter horned lizards
in their backyards for generations to come,” says Diane Barber, curator of ectotherms at the Fort Worth Zoo. “It’s almost a rite of passage for Texans.”


Where They Are, and Aren't

Horned lizards are not the highest conservation priority, as far as lizards go, but they need our help. They’re doing well in much of their historic range — the Panhandle, far West Texas and South Texas; however, they’re not thriving as in the past, when people say they could find 50 of them in an afternoon, and they’ve declined along the urban corridor between Houston and Dallas. They’ve all but disappeared from the eastern third of Texas.

Why are there fewer horned lizards now? Gluesenkamp says it’s the cumulative effect of our human presence on the landscape: fewer large tracts of land, invasive species (fire ants and exotic grasses), agriculture, livestock and urban sprawl, along with changes in land management practices.

Like quail, horned lizards — state-listed as threatened — need a mosaic habitat, a combination of open spaces separated by shrubs. They hunt for food around harvester ant mounds, found out in the open, but also need to thermoregulate, hide from predators and hibernate over winter in the shade and leaf litter. Biologists know that getting that habitat right will mean greater success for the lizards they release.

A Decade of Preparation

Ten years ago, a group of scientists and conservationists gathered to discuss the horned lizard’s plight in Texas. Joining Barber and Gluesenkamp, who at that time was the state herpetologist at TPWD, were TPWD wildlife diversity biologist Nathan Rains and Dean Williams of TCU.

All of us had been inundated with questions from the public,” Rains recalls. “That interest started this conversation and began the process. But we wanted to do horned lizard conservation the right way. We wanted to do our homework first.”

Williams conducted a statewide genetics survey, studying the species from the Panhandle to West Texas to South Texas. The scientists concluded that they could safely move horned lizards within their home region, but it would be unwise to move them outside their own area. The next step was to study how best to release captive- bred lizards into the wild, a complicated matter considering age, quantity, predation and habitat as crucial factors. That’s when the Fort Worth Zoo started a pilot project on a partner’s private ranch to determine best methods for releasing captive- hatched horned lizards.

TPWD, TCU and involved zoos continue to work together as part of the Texas Horned Lizard Coalition, formed to share expertise and identify priorities for conservation of the species.

zoo lady

Mason Lee shows off one of the zoo’s “ambassador” horned lizards, part of a clutch that hatched in July 2017.

Making Babies

Photographer Chase Fountain and I visit Gluesenkamp’s “Lizard Factory” at the San Antonio Zoo to see the preparations underway for future horned lizard releases. Just inside the door sits an incubator with two thermometers and a couple of dozen eggs (laid by wild-caught mothers after capture) the size of your pinky nail, like speckled jelly beans. The eggs are separated into three groups based on viability: some look like perfect little eggs, while others hardly have any shell on them, lacking calcification.

They’re not ready to hatch babies for release yet, conservation manager Bekky Muscher-Hodges tells us, but sometimes the females aren’t aware of the plan and come to the facility already gravid. It takes about two months to hatch the eggs at the proper temperature, around 85-86 degrees.

“When these things hatch, they’ll be the size of a penny,” she tells us.

Muscher-Hodges watches us take off the cover for better photographs with the worried look of a foster mother. Next, we follow her to meet the first breeder lizards brought into the program.

Shelving units along the walls are lined with small terrariums containing sand. Each horned lizard has its own home, complete with a shelter for shade (underneath) and basking on top. Muscher-Hodges and I stop to admire a gorgeous, flame-colored lizard. It’s one of those “Chaparral” beauties from South Texas, with their distinctive red-soil palette of colors.

“That’s one of the kids, but the adults are not that orange,” she points out. “It will be interesting to see at what age they change colors.”

Muscher-Hodges shows me one wild-caught mom that laid 33 eggs when she arrived. Twenty- eight hatched and all survived to chubby young adulthood.

“That clutch size is not abnormal, but that survival rate is unheard of in the wild,” she says. “Everything eats them.”

Gluesenkamp can modify the lab conditions to control when the lizards lay their eggs, so that all factors come together for the best results. The goal is to “headstart” them to get them out of the “everything-eats-them” phase and to make sure they are large enough to take advantage of the full menu of potential prey items available in the landscape, he says.

“Because we can control all elements of their environment in our captive breeding facility, we can control when winter starts and when spring begins in the laboratory,” Gluesenkamp explains. “Usually the animals go down around Halloween to hibernate before breeding, and then come back out in March or April. We’re going to put them down a little early [the end of September], and we’re going to bring them up a little early [January]. That way, when it’s the sweet time of year for horned lizards, we’ll have these larger, healthy babies to turn loose.”


Horned lizard eggs are kept in an incubator at the San Antonio Zoo.

Care and Feeding

The Fort Worth Zoo has been breeding horned lizards since 2001 and has determined optimal husbandry parameters so that other Texas zoos — including the Dallas, Ellen Trout (Lufkin) and Caldwell zoos — can successfully keep them in captivity and participate in reintroduction efforts. The Fort Worth Zoo also directs captive breeding through a genetically managed studbook.

At the San Antonio Zoo, we’re told that the horned lizards are weighed every month.

“In the wild, nobody’s watching over them, looking over their shoulder, making sure they eat all their ants or whatever’s offered them. Here, if we can give them that best advantage or that best start, that’s certainly what we want to do,” Muscher-Hodges says.

What do horned lizards eat? Plenty, and the menu items are a bit pricey.

“See that great big abdomen?” Gluesenkamp points out one lizard’s round, flat belly. “They need a huge stomach to digest this really low- quality prey. Ants aren’t all that digestible, so they have to eat a lot of ants. That’s why they look like big pancakes.”

The couple of dozen lizards on hand now consume 3,000 harvester ants per month ($60 per box) and 11,000 crickets per week, plus roaches, mealworms and waxworms. That monthly bill will skyrocket when the program reaches its goal of 50 breeders and 200 to 400 babies at any time.

“It’s very expensive to keep them in captivity, particularly the food bill,” Gluesenkamp says. “Until we establish our own ant colonies, which we are trying to do, our food bill for our breeders and for rearing up these juveniles is going to
be $800 to $1,000 a month just for ants and crickets.”

big one

At the zoo, each horned lizard has its own terrarium home.

Setting Them Free

Releasing the lizards into the wild is a risky proposition involving several critical factors, including age at time of release, location, number of lizards, danger of predation and food availability.

Releasing babies early helps save on that big food bill, but the younger the lizard, the more likely he’ll be eaten. The sweet spot, age-wise, is around 3 months old, Gluesenkamp thinks.

“When they get about 3 months old, they’re big enough to eat harvester ants,” he says. “The whole menu of prey out there is available to them. It seems like that would be a good time to turn them loose.”

Gluesenkamp will concentrate on higher numbers of younger lizards so no predator can wipe out the entire batch. He wants to replicate what happens in the wild, where 20 breeding females could hatch 600 babies in one season.
“You never hear of anyone releasing 12 quail or 20 bass,” he points out. “You start with juveniles and you dump a ton of them on the landscape.”

Where are the best places to release horned lizards? How do we identify places in Texas where we think horned lizards might persist and thrive, where we can establish viable populations?

Technology now helps locate suitable private properties. TPWD’s Amie Treuer-Kuehn developed a high-resolution map of Texas that helps reveal conservation opportunity areas — places with the right terrain, plant communities and food sources for particular species. Gluesenkamp can use this map to score and rank sites for horned lizard release.

“I’m looking for sites that have at least 250 acres of high-quality habitat, preferably more, preferably buffered by some better-than-average- quality habitat or connected to other large areas,” Gluesenkamp says. “I want to build populations that will metastasize to other sites so we’ll actually see horned lizards back on the landscape.”

Gluesenkamp lists his criteria for good sites: Are they within the historic range of the species? Do they currently have horned lizards on the landscape (no releases take place where there are existing populations)? Did they ever? What’s the acreage? What are the landowner’s management approaches? Are the landowners willing to manage for horned lizards in perpetuity?

big boy

Finding them Again

Horned lizards aren’t difficult to catch, but they can be difficult to observe because they’re very good at hiding and are well-camouflaged. That poses problems for conducting post-release follow-up surveys. Even skilled human searchers find only about 10 percent of the lizards that are present in any habitat.

How do we know that we see only 10 percent? Genetics provides the answer.

TCU’s Williams and his students did visual surveys for lizards, but also collected scat. Horned lizard scat is distinctive, mostly ant body parts with a dollop of white uric acid that looks like toothpaste. Genetic analysis showed that the scat came from 10 times more lizards than they had observed.

Traditionally, adult horned lizards have been fitted with radio telemetry, but these young lizards are too small to attach the tiny backpacks, and at $180 each, they are too expensive to use on hundreds of lizards. The problem is how to track the released lizards to gauge success.

The answer? Dogs are one possibility. Of course, we’ve all seen dogs trained to track all different kinds of wildlife, and not just for hunting retrieval. Dogs are used to locate box turtles, birds, bedbugs and Louisiana pine snakes, among others.

Paul Bunker, owner of Chiron K-9, is a former military dog trainer who wanted to use his
skills for conservation and, in collaboration with Gluesenkamp, submitted a proposal for Department of Defense funding to establish a lizard dog program. His program solicits volunteers from the community to take in a shelter dog and go through the training program at Texas A&M University
so that the dog and the trainer both become competent lizard hunters, on call to help.

The dogs are trained using the shed skin and feces from the captive lizards for scent examples, even though horned lizards don’t really have an odor to us.

“We hope to get a half-dozen dogs and trainers on the property for a day,” Gluesenkamp says. “We don’t yet know how good dogs will be at sniffing lizards, but if other studies have been any sort of guide, they’re going to be wildly successful.”

What's Next?

Gluesenkamp’s team hopes to release their first batch of juvenile lizards in May or June of 2019 and grow their program.

“Our plan is to actually build a freestanding Lizard Lab using shipping containers,” he tells us. Visitors to San Antonio will one day see the painted sides of the lab promoting the zoo along the highway.

In the meantime, it is business as usual at
the Fort Worth Zoo as staff and other partners, including the Dallas Zoo, continue to produce offspring for reintroduction and conduct research in the northern part of the state.

“Captive breeding for reintroduction can be costly, especially for a specialized feeder such as the horned lizard,” Barber explains. “It will also take a large number of released lizards over a long period of time to establish a new population in the wild, especially in an environment with numerous predators.”

That could mean many, many boxes of harvester ants. Aside from small grants from TPWD for startup support, all of this work is supported by private donations. You can donate to the San Antonio Zoo program at sazoo.org/about/donate/texashornedlizard or the Fort Worth Zoo program at www.fortworthzoo.org/donate-now.

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