DRAGONS OF THE INFERNAL REALM:

An Introduction to the Texas alligator lizard.

by Roy Arthur Blodgett

Deep within the limestone cuts and canyons of the Texas hill country - slinking among the live oak, ball moss, and maidenhair fern - dwells one of North America’s most charismatic Saurians: the Texas alligator lizard (Gerrhonotus infernalis). In the vivarium, they make for one of the best pet lizards one could ask for, but before diving into the specifics of their husbandry, let’s begin with a basic outline of their natural history.

Natural history

Largely considered the largest of the alligator lizards, infernalis is an impressive lizard in the family Anguidae, attaining lengths of up to two feet (60cm), a metric that sets them distinctly apart from their smaller relatives in the genus Elgaria. Though largely distributed through central and eastern Mexico, from Chihuahua in the north, south to Hidalgo, their range also extends into south-central Texas, primarily across the Edwards Plateau and Balcones Escarpment, where they are strongly associated with the oak woodlands and limestone canyons of the Hill Country.

Texas alligator lizards are diurnal, and though often classified as terrestrial, they are far more arboreal in habit than their cousins in the genus Elgaria, readily climbing shrubs, trees, and rock faces with regularity, while making good use of their powerful, semi-prehensile tails. In Texas, they’re most commonly observed within limestone crevices or vegetation in riparian canyons or woodland habitats, but in some areas they are known to occupy more open, rocky slopes and adjacent areas. They are highly insectivorous, employing an active hunting strategy, foraging through leaf litter, and preying upon a variety of insects and arthropods. Their dietary preferences are largely indiscriminate, including but not limited to katydids, mantids, phasmids, grasshoppers, spiders, and caterpillars. It is also presumed they will raid the occasional rodent or songbird nest.

Dragons of the Infernal Realm

Acknowledgements: I would be remiss not to extend special gratitude to Justin Munsterman, Connor Wardle, Chad Lane, Dustin Grahn, and Armen Keuylian, whose insights and enthusiasm for Gerrhonotus, among other alligator lizards, have contributed greatly to my experience keeping these lizards.

Author’s Bio:

Roy Arthur Blodgett is the sole proprietor of Wellspring Herpetoculture, and keeps an eclectic array of New World reptiles and amphibians with a focus on naturalistic, biotope husbandry. He is passionate about the value of herpetoculture in our rapidly changing world, and his background as a naturalist and ecological educator strongly informs his practice. He is constantly striving to progress his husbandry and encourage a broader range of natural behaviours in the animals in his care. He also co-hosts the Project: Herpetoculture Podcast, which features long-form discussions exploring the art, practice, and discipline of keeping reptiles and amphibians.

Sexual dimorphism is expressed in Texas alligator lizards through several obvious characteristics. Males tend to attain a larger overall size, with much larger and broader heads. Females are more slightly built, with larger and longer abdomens relative to the size of their heads. Males also have a pronounced hemipenal bulge at the vent, especially evident in comparison to females when held side by side. In terms of reproduction, most sources cite that mating occurs in the fall. Copulation usually occurs in a terrestrial setting, with the male grasping the base of the female’s neck with his mouth. An oviparous species, the Texas alligator lizard usually lays an annual clutch averaging from ten to twenty eggs. Larger clutches are not uncommon, especially in large, well-conditioned females of the species.

Gerrhonotus infernalis is currently listed as ‘Least Concern’ by the IUCN. That said, there is no mistaking that much of their range and habitat has been significantly impacted by human development. Because most of their native habitat falls within the borders of private landholdings, their longterm well-being is worthy of weighty consideration.

Housing

Given their relatively sedate behaviour and modest size, Texas alligator lizards are quite reasonable to satisfy in terms of vivarium dimensions, especially in comparison to more active species of similar size, such as dwarf monitors (which require very large vivaria, given their hyperactive behaviour). In my case, I have usually housed oppositesexed pairs in vivaria measuring approximately 3 feet long by 2 feet deep by 2 feet tall (~90cm by 60cm by 60cm), which, when well provisioned with complex decor and climbing opportunities, provides sufficient space and opportunity for movement. However, larger vivariums, whenever possible, are preferred. Gerrhonotus will make full use of the space offered to them.

As is always the case, the keeper’s climate and reptile room conditions will bear the greatest influence on choosing the most suitable material for the vivarium itself. Living in a Mediterranean climate in central California and having a reptile room that is difficult to reliably regulate year-round, I typically use PVC habitats with acrylic or sliding glass doors, which have the benefit of retaining

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ADJUSTABLEFEET some heat and humidity to provide a more stable environment within the vivarium. For those who live in more stable climates, or who can reliably regulate temperature and humidity on the full room scale, a broad array of options might be utilized, such as glass, wood, or even screen.

To furnish the vivarium, I provide a faux rock background to maximize usable surface area and outfit the space with branches throughout to allow for climbing and basking at varying temperatures and ultraviolet levels. The substrate is a deep mix of decomposed granite, play sand, and topsoil or peat moss, topped with a generous layer of leaf litter to encourage burrowing and foraging behaviour. Live plants, such as agaves, grasses, tillandsias, or maidenhair ferns provide cover and offer valuable enrichment and stimulation. Lastly, I include a few slabs of bark or slate, beneath which the lizards can find refuge, as desired.

Climate control and replication

Subject to a northern latitude, the region where Gerrhonotus infernalis natively occurs expresses significant fluctuation in daylight, temperature, and precipitation throughout the calendar year. The daylight cycle peaks in late June with a roughly 14-hour day, descending to a trough of 10 hours of daylight in late December. Temperatures follow a similar arc, peaking with average temperatures of 34-36°C in late summer, and descending to average daytime temperatures of 16-21°C. Nighttime temperatures average around 21°C during the summer and reach annual lows of 5°C during the winter. There are also significant seasonal rhythms expressed in precipitation, with a pronounced wetter season during the summer, punctuated by a dry winter. Replicating these factors of photoperiod, average temperature, and precipitation within the vivarium is essential to the longterm well-being and propagation of Texas alligator lizards.

To meet the appropriate provisions of visible light, ultraviolet radiation, and infrared radiation, I utilize three types of lighting in my Texas alligator lizard vivaria. Standard PAR38 or PAR30 halogen bulbs heat the vivariums to average ambient temperatures of 25-29°C while providing a localized basking area exceeding 38°C. Halogens are particularly adept in emitting near-infrared radiation, allowing the lizards to thermoregulate efficiently as they would in nature. Linear high-output T5 bulbs are provided for ultraviolet A+B radiation, creating a gradient of UVI values ranging from 0 to 3.0 throughout the vivarium. Choosing the right bulb and UV output is dually dependent on the distance of the bulb from the basking area and the specific bulb’s UV output percentage, and as such can vary widely, and the keeper must determine the appropriate bulb based on these factors. For visible light, I utilize linear LEDs (~6000K), which flood the enclosures with rich, bright light capable of supporting live plants. In concert, these three types of lighting provide a broad spectrum and a sufficient (if admittedly shoddy) replication of natural sunlight for the needs of the lizards. Furthermore, when sequenced correctly with the use of timers, one can roughly simulate the sun’s light as it rises, peaks, and sets across the day and fluctuates throughout the seasons.

To simulate the onset of the monsoon rains of late summer, I regularly mist the vivarium during the summer monthsperhaps three to four times per week. For this task, hand misting with a pump sprayer, or utilizing an automatic misting system, is equally appropriate. In the drier seasons, I continue to provide a shallow water bowl, which I overfill regularly to provide a moisture gradient within the substrate. Occasionally I observe the lizards drinking from their bowls, but it is an admittedly rare occurrence, suggesting to me that the majority of their hydration needs are met by the moisture content of their prey, and the provision of humid refugia to avoid desiccation.

Diet and supplementation

Gerrhonotus are capable predators of a wide array of insects, arthropods, and small vertebrates, employing an active foraging strategy to find prey, which they slowly stalk until within striking range. Once close, the lizards curve their forebodies into an S-shape and lunge with startling precision to capture their quarry within their powerful jaws. Just before lunging, it is not uncommon for them to twitch their tails in a cat-like manner, perhaps as a distraction to confuse their prey.

In the vivarium, crickets, roaches, grasshoppers, phasmids, katydids, mantids, caterpillars, spiders, flies, fly larvae, and beetle larvae are all accepted prey. Given their relatively sedate hunting strategy and slow metabolisms in comparison to more active species, Texas alligator lizards also respond very well to tong feeding. They are strongly food-motivated, and I have found that encouraging the lizards to pursue their prey on the tongs is a good way to encourage exercise and familiarize the lizards with their keeper. Mine readily recognize the food cup and greedily approach the vivarium door upon my approach, showing no fear of me whatsoever and willingly climbing out onto my hand or arm in pursuit of an insect on the tongs!

In terms of supplementation, I utilize high-quality multivitamin and calcium products formulated for reptiles to dust feeder insects. My rotation is usually two to three feedings of insects dusted with multivitamins, followed by one dusted with calcium, repeating the rotation and remaining attentive to any need for adjustment. Reproductively active females should be offered additional calcium to ensure they have sufficient resources for egg production. As with all of the lizards in my care, the Gerrhonotus are kept under high-quality UV-producing bulbs, and as such I avoid supplements with added D3 to avoid the possibility of hypervitaminosis.

Breeding

As far as I have observed, Texas alligator lizards have been inconsistently bred and are poorly represented in herpetoculture, at least in recent years. This is likely due in part to their relative rarity within the practice, alongside the generally lacking commercial demand for the species. That said, I feel that they show remarkable appeal and consider them worthy of more dedication in herpetocultureespecially given their resilience, beauty, and fecundity.

As of this writing, I have only attempted one pairing of infernalis, after raising my adults from neonates Though I never observed copulation, I suspect it occurred in the fall, after my late summer attempts to simulate the monsoon rains with greater misting frequency, as well as much more frequent offering of food (~3-4 feedings per week). Like many species subject to seasonal scarcity, I believe that the species is triggered to breed by a combination of heavy precipitation, change in temperature, and resource abundance. That said, only a combination of continued refinement and consistent success over time will clarify the exact factors which reliably elicit courtship behaviour and breeding in this species.

Over the early winter, the female’s abdomen began to noticeably swell, and on January 19th she laid an impressive first clutch of 28 eggs beneath the water bowl - where the substrate was cool and moist. Having heard from the great herpetologist, Harry Greene, that female Gerrhonotus are known to guard their eggs, I gently removed the water bowl and was not surprised when met with a hissing and protective mother who began lunging at me with mouth agape. Though tempted to leave the eggs with the female, given her impressive display and clear commitment to her eggs, I ultimately decided to remove them for placing in the incubator, where I expected the more stable temperatures and humidity might result in a better hatching outcome.

All 28 eggs were placed in simple incubation containers, which featured ventilated plastic trays elevated over moist, fired clay substrate. I also added a layer of wrung sphagnum moss on top of the eggs to help maintain humidity. I set the incubator to 80 degrees F (26.6 C) with a night drop to 78.5 degrees F (25.8 C), anticipating an incubation period of anywhere between 50-70 days and left the eggs to hatch. Disappointingly, over the following weeks, the majority of the eggs failed, perhaps due to excessive moisture and higher-than-optimal temperatures. In later correspondence with another keeper who has been successful in hatching infernalis, Laurence Paul, I was informed that the eggs consistently hatch very well at lower overall temperatures than those I employed. Regardless, after 48 days the first neonates began to pip, and by the 50th day, nine hatchlings had successfully emerged from their eggs.

Rearing of neonates

Neonate Texas alligator lizards are beautifully patterned and show much more pronounced contrast than adults of the species. Though diminutive and somewhat delicate, I’ve found that, in most respects, their husbandry tracks very closely with that of their mature counterparts. All that hatched were born with strong appetites, and after a few days took to feeding on appropriately sized insects. Flightless fruit flies, bean beetles, small caterpillars, buffalo beetle larvae (Alphitobius diaperinus), roach nymphs, and small crickets were all accepted prey, with a particular preference expressed for crickets. To avoid the potential of aggression or tail and toe nops between conspecifics, I fed the neonates every other day.

Though I was warned about potential aggression issues with housing the neonates communally, I found that they exhibited no aggression toward one another and did not nip one another’s toes or tails when kept in groups of 5 to 7 individuals in a roughly 60x45x45cm or equivalent space. With sufficient cover, easily provided by some leafy branches of live oak, the neonates showed very little fear or reaction to my approach, seemingly confident in their camouflage. The great majority of the time, they could be observed basking among the twigs and branches of their vivaria, springing to life with cat-like movements whenever prey was offered.

With a regular feeding schedule, Gerrhonotus grow quickly, and mine reached adult size and sexual maturity at approximately 18 months, at which point I began to observe some territoriality between the males. For this reason, it is best to house them individually, or in oppositesexed pairs as they approach maturity to avoid stress and potential injury between conspecifics. I have never observed worrying behaviour between opposite-sexed pairs housed together year-round, provided they are offered sufficient space to avoid one another as desired. Overall, they are very tolerant of one another and can often be observed coiled togethe`r in repose.

Conclusion

In summary, the Texas alligator lizard is an excellent candidate for the beginner to intermediate reptile keeper. As juveniles and adults, their durability and tolerance to extremes provide a broad margin of error in husbandry, making them an excellent species for the less experienced herpetoculturist to learn from in developing a skill set. Simultaneously, their relative rarity in herpetoculture and impressive fecundity are attractive considerations for more advanced keepers and breeders seeking a viable project. Furthermore, their charisma and interesting behavioral repertoire are sure to capture the interest of anyone with an appreciation for natural history. With a bit more focus on bloodline diversity from dedicated herpetoculturists, I have little doubt they could become a mainstay in the practice for generations to come.